This page is supervised by specialist physicians at IC Clinic Ikebukuro, a 5-minute walk from JR Ikebukuro Station.
🚨 “My epidermoid cyst has turned red and is painful…”
These symptoms are a warning sign!
💡 An inflamed epidermoid cyst is a more serious condition than an ordinary epidermoid cyst. If you have pain and swelling, please see a specialist promptly.
An inflamed epidermoid cyst (atheroma) is a cyst in which bacteria have entered at an early stage, leading to inflammation and suppuration.
Because an inflamed epidermoid cyst develops from an ordinary cyst and progresses to cause pain, it should not be left untreated — prompt treatment is necessary.
⚠️ Warning Signs
✅ The cyst is red and swollen
✅ Throbbing pain
✅ Warm to the touch
If even one of these applies, please seek medical attention right away!
🔥 What Is an Inflamed Epidermoid Cyst (Atheroma)? Symptoms and Causes
💡 This section explains the basic symptoms and causes of an inflamed epidermoid cyst. Understanding the differences from an ordinary cyst is important.
In its early stages, an epidermoid cyst typically causes no pain and can be felt simply as a firm lump under the skin.
However, when bacteria enter and cause inflammation, the cyst becomes red, swollen, and painful.
This is referred to as an inflamed epidermoid cyst or a suppurative epidermoid cyst.
※ Throughout the rest of this article, the term “inflamed epidermoid cyst” will be used consistently.
⚠️ Risks of Leaving an Epidermoid Cyst (Atheroma) Untreated: Suppuration and Unpleasant Odor
💡 This section explains in detail the serious problems that can arise from leaving an epidermoid cyst untreated. Reading this will help you understand why early treatment is important.
The greatest danger of leaving an epidermoid cyst (atheroma) untreated is that over time, the waste matter accumulated inside can decompose, or bacteria can enter from outside and cause infection, leading to inflammation and suppuration.
- 🔴 Progression of Inflammation and Suppuration:
The interior of a cyst tends to accumulate dead skin cells and sebum, creating an environment where bacteria can multiply easily.
In particular, when bacteria enter through the small opening (“punctum”) that connects the cyst to the skin surface, infection can spread rapidly and trigger inflammation.
Once inflamed, the cyst becomes red and swollen, accompanied by intense throbbing pain.
As the condition worsens, pus accumulates inside, the cyst takes on the appearance of a boil, feels warm to the touch, and the overlying skin begins to bulge. - 👃 Development of an Unpleasant Odor:
The old keratin and sebum that accumulate inside the cyst are broken down by bacteria, producing a distinctive unpleasant odor.
This odor can become strong enough to be noticeable to those around you, and may cause significant psychological distress in daily life and social situations. - 💥 Rupture and Increased Treatment Complexity:
When suppuration advances and the internal pressure reaches its limit, the cyst may spontaneously rupture, releasing pus and decomposed contents.
Although pain may temporarily subside, bacteria can more easily re-enter through the ruptured wound, risking the spread of inflammation to surrounding skin or the development of a widespread skin infection known as cellulitis.
In addition, a ruptured cyst is prone to adhesion with surrounding tissue, which means that subsequent surgery becomes more complex and scarring is more likely. - 📏 Enlargement:
Repeated episodes of inflammation and rupture can cause the cyst to grow larger, compressing surrounding tissue and becoming visibly prominent as a large lump.
As the cyst grows, the scope of surgery expands accordingly, affecting both the cost and the recovery period.
As described above, leaving an epidermoid cyst (atheroma) untreated is not merely a cosmetic issue — it can significantly increase the risk of pain, odor, and more serious infections, and may complicate treatment.
For this reason, if you notice symptoms of an epidermoid cyst, it is important to visit a medical facility promptly and receive appropriate treatment.
🚫 Never Attempt to Self-Treat (Pop) an Epidermoid Cyst (Atheroma)
💡 Attempting to pop an epidermoid cyst yourself is extremely dangerous. This section explains why, and the risks involved.
If you are bothered by an epidermoid cyst (atheroma) and are tempted to “just pop it yourself” because of its appearance or discomfort, please be aware of the following.
Self-treatment of an epidermoid cyst should never be attempted.
Attempting to pop it yourself carries a range of serious risks and is very likely to worsen your condition.
Attempting to pop an epidermoid cyst yourself can cause the following problems.
- 🦠 Greatly Increased Risk of Bacterial Infection:
Using fingers, fingernails, or an unsterilized needle to try to pop a cyst damages the skin, greatly increasing the likelihood that large numbers of bacteria will enter the interior of the cyst.
This can cause inflammation to worsen further, accelerate suppuration, and raise the risk of serious infections such as cellulitis in the surrounding skin. - 😣 Worsening Inflammation and Increased Pain:
Forcing the cyst open can rupture the internal sac and cause its contents to spread into surrounding tissue, triggering a severe inflammatory reaction.
This can significantly worsen symptoms such as intense pain, swelling, and warmth, and can greatly interfere with daily activities. - 🩹 Scar Formation:
When inflammation or infection becomes severe, noticeable scarring is more likely to form during the healing process.
This may present a cosmetic concern, particularly in visible areas such as the face. - 🔄 Risk of Recurrence:
The fundamental treatment for an epidermoid cyst involves completely removing not only the contents but also the “sac” (cyst wall) that is the underlying cause.
Even if you manage to pop it yourself, if any part of the sac remains, the contents will accumulate again over time and recurrence is highly likely.
Repeated recurrences can make the cyst progressively more difficult to treat. - ⏰ Delayed Diagnosis:
Attempting self-treatment may delay the timing of seeking medical attention.
While rare, there are malignant tumors that can resemble an epidermoid cyst in appearance.
Consulting a specialist allows for an accurate diagnosis and the formulation of an appropriate treatment plan.
An epidermoid cyst (atheroma) requires appropriate treatment by a dermatologist or a specialist in plastic and reconstructive surgery.
If you have any concerning symptoms, do not attempt to manage them yourself — please visit a medical facility promptly.
A specialist will recommend the most suitable treatment approach based on the presence of inflammation, the size of the cyst, and its overall condition.
📈 Why Does an Epidermoid Cyst (Atheroma) Grow Larger, and What Should You Do?
💡 This section explains in detail why epidermoid cysts grow larger and why you should address them before they become very large.
Once an epidermoid cyst (atheroma) forms, it almost never resolves on its own and in most cases will gradually enlarge over time.
The main reason for this growth is the continuous accumulation of old keratin and sebum that are constantly produced inside the sac.
- 🔸 Continuous Production of Contents:
The sac of an epidermoid cyst is formed from a portion of skin that has invaginated inward.
As a result, the cells lining the inside of the sac continue to produce keratin just as normal skin does.
As this keratin and sebum accumulate inside the sac, the cyst gradually expands. - 🔥 Repeated Episodes of Inflammation:
When an epidermoid cyst becomes inflamed, the surrounding tissue swells and the cyst itself may feel temporarily larger.
Even after inflammation subsides, contents accumulate again, and with each subsequent episode of inflammation the cyst tends to become progressively larger in a vicious cycle.
Repeated inflammation can also thicken the sac wall and cause adhesion to surrounding tissue, further contributing to enlargement. - 👕 Friction and Physical Irritation:
Constant rubbing from clothing, physical pressure, or other forms of friction that cause the cyst to be chronically irritated can make it more prone to inflammation, which in turn may contribute to its growth.
💊 What to Do If an Epidermoid Cyst (Atheroma) Has Grown Larger
As a cyst grows larger, symptoms such as pain and odor become more pronounced, and practical inconveniences increase — for example, the cyst catching on clothing or getting in the way when sitting.
Moreover, the larger the cyst becomes, the wider the incision required during surgery, and the more likely it is that scarring will remain.
Therefore, if you notice that an epidermoid cyst (atheroma) is growing larger, please consider the following points and visit a medical facility promptly.
- 🏥 See a Specialist Early:
Treating a cyst while it is still small reduces the burden of surgery and makes it easier to minimize scarring.
Before it grows larger, consult a specialist such as a dermatologist or plastic and reconstructive surgeon for a proper diagnosis and discussion of treatment options. - 🔪 Consider Appropriate Surgery:
The definitive treatment for an epidermoid cyst is surgery to completely remove the “sac” (cyst wall) along with its contents.
Surgery is ideally performed when there is no active inflammation.
If inflammation is present, the first step is typically a procedure to reduce inflammation (such as incision and drainage), followed by a separate procedure at a later date to remove the sac. - 🚫 Do Not Self-Diagnose or Self-Treat:
A larger cyst has even greater internal pressure, so attempting to pop it yourself significantly increases the risk of more severe infection and inflammation.
Never touch or attempt to pop a cyst on your own.
The size and condition of an epidermoid cyst varies from person to person.
Receiving a specialist’s diagnosis and selecting the treatment approach most suited to your individual situation is the first step toward a safe and effective resolution.
🔴 Symptoms of an Inflamed Epidermoid Cyst
💡 This section explains in detail the specific symptoms of an inflamed epidermoid cyst. If you are experiencing these symptoms, please seek medical attention promptly.
When an epidermoid cyst becomes inflamed or suppurates, it becomes red, swollen, and painful.
In cases of severe suppuration, the sac-like structure beneath the skin is destroyed and pus accumulates inside.
This condition is also referred to as an abscess, and it is accompanied by significant pain.
🦠 Medical Causes of Inflammation in an Epidermoid Cyst
💡 This section explains from a medical perspective the mechanism by which an epidermoid cyst becomes inflamed.
The medical cause of inflammation is bacteria entering through the small opening (“punctum”) at the center of the cyst.
An epidermoid cyst is a benign tumor that forms when waste matter such as dead skin cells and sebum accumulates beneath the skin.
Because an epidermoid cyst does not resolve on its own, it gradually develops into a larger sac-like structure as the condition worsens. When bacteria enter this sac, inflammation is triggered.
(※ For reference: What Is an Epidermoid Cyst?)
The interior of the cyst sac is structurally devoid of the immune cells responsible for eliminating bacteria and other pathogens, which means it is particularly susceptible to bacterial infection.
In particular, touching or trying to pop the cyst out of habit can introduce bacteria and trigger an inflamed epidermoid cyst, so please avoid touching it as much as possible.
🧠 Psychological Causes of Inflammation in an Epidermoid Cyst
A sense of “psychological complacency” — such as thinking “it’s just a lump, I can leave it alone” or “it’s a benign tumor, so there’s no problem leaving it” — may also contribute to the development of an inflamed epidermoid cyst.
As noted above, an epidermoid cyst does not resolve on its own and is susceptible to bacterial infection.
Nevertheless, some patients leave their cyst untreated and only visit a medical facility once inflammation and pain have developed.
If you are reading this article, we strongly encourage you not to leave your cyst untreated, and to contact a medical facility that treats epidermoid cysts as soon as possible.
⚠️ [Important] Seek Medical Attention Before an Inflamed Epidermoid Cyst Ruptures
💡 This section explains in detail the dangers of a ruptured inflamed epidermoid cyst and the steps you can take to prevent it.
An inflamed epidermoid cyst represents an escalation from an ordinary cyst and carries increased risks.
Unnecessary touching can cause it to rupture, so please visit a clinic for examination before that happens.
In fact, an inflamed epidermoid cyst carries a risk of rupturing even through ordinary daily activities.
The following sections cover the causes of rupture in an inflamed epidermoid cyst and what to do if the contents begin to discharge.
Being aware of this information can help prevent a worsening of symptoms caused by rupture before you are able to seek medical attention.
💥 Causes of Rupture in an Inflamed Epidermoid Cyst
An inflamed epidermoid cyst can rupture from even a slight impact.
When a cyst becomes infected with bacteria and develops into an inflamed cyst, the sac-like structure of the cyst becomes fragile and prone to tearing.
What begins as a firm lump gradually becomes softer and warm to the touch as inflammation progresses.
Once softened, even a minor knock or pressure can cause it to rupture and release pus.
When the sac ruptures, pus spreads to the surrounding area, causing the inflammation to worsen further.
The area becomes increasingly red and swollen, and as the condition advances the opening may become eroded and wider, with malodorous pus and cyst contents being discharged.
This state of spontaneous pus discharge is referred to as “spontaneous rupture” (自壊, jikaï).
🩹 What to Do If a Cyst Ruptures and Discharges Its Contents
If a cyst ruptures and discharges its contents during daily life, seek medical attention as soon as possible.
In cases of severe suppuration, a procedure may be performed in which the skin is incised and the pus accumulated inside is drained — this is known as incision and drainage.
Because this involves a surgical procedure, it is advisable to visit a hospital or clinic with experience in epidermoid cyst surgery.
💡 If you have already popped your cyst, please consult IC Clinic.
If you accidentally ruptured your cyst by touching it and it is now red and swollen, please contact IC Clinic right away.
Inflamed epidermoid cysts are prone to scarring, so treatment should be sought as soon as possible.
We will propose a treatment approach designed to minimize discomfort and reduce the visibility of any scarring, so please feel reassured in leaving your care to us.
Epidermoid cyst surgery at our clinic is covered by Japanese public health insurance, so you can feel reassured about the cost as well.
Surgery is typically completed in around 20 minutes at most, making same-day discharge possible.
If you have any concerns about an epidermoid cyst, please do not leave it unaddressed — feel free to consult IC Clinic.
✂️ Treatment for Epidermoid Cysts (Atheroma) | Surgery for Complete Removal
💡 This section explains in detail the fundamental treatment for epidermoid cysts. Understand why medication alone is not effective and why surgery is necessary.
An epidermoid cyst (atheroma) cannot be treated with medication alone.
The fundamental treatment requires surgery to completely remove the “sac” (cyst wall) along with its accumulated contents.
This section explains the main surgical techniques for treating an epidermoid cyst (atheroma), their characteristics, and the possibility of same-day surgery.
🔧 Surgical Techniques for Epidermoid Cysts (Atheroma): Punch Excision and Excision with Fusiform Incision
There are two main surgical techniques for treating an epidermoid cyst (atheroma): punch excision (punch-out method) and excision with fusiform incision.
The choice between these techniques is determined by the physician based on factors such as the size, location, and presence of inflammation.
| Technique | Characteristics (Advantages) | Disadvantages / Points to Note | Indications |
| Punch Excision (Punch-Out Method) | ・Minimal scarring: Contents and sac are removed through a small opening of a few millimeters in diameter, resulting in a less noticeable final scar. ・Faster recovery: Little or no suturing is required, so there is a tendency for less post-operative swelling and discomfort and a shorter healing period. ・Less physical burden: The procedure is completed in a short time and can be performed under local anesthesia only. |
・Not suitable when inflamed: When inflammation is significant or suppuration is present, the sac may be fragile and complete removal may not be possible, so this technique is often not chosen in such cases. ・Recurrence risk: In rare cases, a small portion of the sac may remain, leading to possible recurrence. ・Requires skill: Accurate removal of the sac through a small opening demands a high level of surgical expertise. |
・Non-inflamed cysts: Cysts in a settled state with no redness or pain. ・Relatively small cysts: Those approximately 2 cm in diameter are most commonly indicated, though larger cysts may be treatable with sufficient skill. ・Particularly recommended for cysts in cosmetically sensitive areas such as the face or neck where minimal scarring is desired. |
| Excision with Fusiform Incision | ・Reliable removal: Because the skin is incised more widely, the entire cyst sac can be removed under direct visual confirmation. ・Applicable even with inflammation: In cases of significant inflammation or suppuration, the cyst may be incised to drain the pus, and the sac removed at the same time (though in severe cases, drainage may be performed first and the sac excised at a later date). ・Low recurrence risk: Because the entire sac can be completely removed, the risk of recurrence is very low. |
・More noticeable scarring: Because a wider incision is required relative to the size of the cyst, scarring tends to be more extensive than with the punch excision technique. ・Longer recovery: Suturing is usually required, and healing may take longer, including the period until suture removal. ・Slightly greater physical burden: Performed under local anesthesia, but is more invasive than the punch excision method. |
・Inflamed cysts: Cysts that are red, swollen, or contain accumulated pus. ・Larger cysts: Relatively large cysts of 3 cm or more in diameter, or cysts located deep beneath the skin. ・Cases where punch excision is not feasible, or where the cyst has ruptured and become adherent to surrounding tissue. |
🎯 What Is Punch Excision (Punch-Out Method) for Epidermoid Cysts (Atheroma)?
Punch excision, also known as the “punch-out method,” is a surgical technique in which a small opening is made at the punctum at the center of the cyst — or by creating a new small incision — and a specialized instrument is used to extract the cyst sac through this opening in a coring motion.
📋 Procedure Overview:
📌 Local anesthesia: Local anesthetic is first injected into the cyst and surrounding area.
📌 Small incision or perforation: A small opening approximately 2–5 mm in diameter is made at the punctum of the cyst, or a new small incision is created.
📌 Evacuation of contents: Pressure is applied through the small opening to evacuate the keratin, sebum, and other contents accumulated inside the cyst.
📌 Removal of the cyst wall: Once the contents have been evacuated, the sac-like structure (cyst wall) is carefully peeled away and extracted using specialized forceps.
Care is taken throughout to avoid rupturing the sac.
📌 Completion: After confirming that the sac has been completely removed, the wound is typically left to heal naturally without suturing.
In some cases, a minimal number of sutures may be placed.
The wound is small and generally closes within a few days.
✨ Advantages:
🔸 Cosmetically favorable: The final scar is very small and less noticeable — this is the primary advantage of the technique.
It is particularly suitable for cosmetically sensitive areas such as the face and neck.
🔸 Less physical burden: The procedure is short (typically around 10–20 minutes), with minimal blood loss, reducing the physical burden on the patient.
🔸 Faster recovery: Because the wound is small, post-operative swelling and discomfort are minimal and return to daily activities is typically quick.
⚠️ Points to Note:
Punch excision is suitable for non-inflamed cysts of relatively small size.
When inflammation is significant or suppuration is already present, the sac may be too fragile for complete removal, and excision with fusiform incision is often selected instead.
🔪 What Is Excision with Fusiform Incision for Epidermoid Cysts (Atheroma)?
Excision with fusiform incision is a surgical technique in which the skin directly overlying the cyst is incised and the entire cyst sac is removed under direct visual confirmation — the most reliable surgical approach available.
📋 Procedure Overview:
📌 Local anesthesia: Local anesthetic is injected into the cyst and surrounding area.
📌 Skin incision: The skin is incised in a fusiform (leaf-shaped) pattern along the long axis of the cyst, sized to match the cyst.
📌 Dissection and removal of the cyst wall: The cyst sac (cyst wall) is carefully dissected away from surrounding tissue and completely removed.
Care is taken throughout to avoid rupturing the sac.
📌 Hemostasis and suturing: Bleeding is controlled and the skin is carefully sutured closed.
The skin surface is typically closed with sutures.
📌 Completion: The wound is covered with gauze or tape for protection.
A follow-up visit for suture removal will be required at a later date.
✨ Advantages:
🔸 Reliability: Because the entire sac can be removed under direct visual confirmation, the risk of residual tissue is low, and the risk of recurrence is very low — this is the primary advantage of the technique.
🔸 Broad applicability: This technique is applicable to a wide range of cyst conditions, including inflamed cysts, suppurating cysts, large cysts, and cysts of complex shape.
When inflammation is severe, the cyst may first be incised to drain the pus, and the sac excised once the inflammation has settled — a two-stage surgical approach.
⚠️ Points to Note:
Because the excision with fusiform incision technique involves a wider area of incision compared to punch excision, scarring tends to be more noticeable.
In particular, the shape and length of the scar may be a cosmetic consideration for cysts in visible areas such as the face.
Recovery time also tends to be somewhat longer than with the punch excision method.
The choice between techniques is made by taking into account the overall condition of the patient’s cyst and their preferences regarding scarring, and should be decided in thorough consultation with your physician.
🏥 Is Same-Day Surgery Possible for Epidermoid Cysts (Atheroma)?
Many epidermoid cysts (atheroma) can be treated on the same day.
This is because the surgery itself is performed under local anesthesia and is completed in a relatively short time.
- 📋 Typical Cases:
For small, stable, non-inflamed cysts, surgery can be performed on an outpatient basis under local anesthesia, allowing the patient to go home the same day.
The duration of surgery varies depending on the size and number of cysts and the technique selected, but in most cases is completed in approximately 10 to 30 minutes.
After surgery, the patient receives wound care and post-operative instructions and can go home immediately. - ✅ Advantages of Same-Day Surgery:
- Minimal time commitment: Because hospitalization is not required, the impact on daily life and work is minimized.
- Less psychological burden: There is no need to experience an unfamiliar hospital stay, and recovering in the comfort of your own home reduces psychological stress.
- Lower financial burden: Because there are no hospitalization fees, the total medical cost is reduced.
- ⚠️ Exceptional Cases (Where Hospitalization May Be Required):
However, not all epidermoid cysts can be treated on the same day.
Hospitalization, or more careful planning, may be required in the following situations. - Very large cysts: In the case of very large cysts exceeding several centimeters in diameter, greater blood loss or more complex post-operative care may be anticipated, and hospitalization for observation may be necessary.
- Severely inflamed or suppurating cysts: When a cyst has formed an abscess with severe inflammation, an initial procedure to incise and drain the pus may be performed, with surgery to remove the sac carried out a few days later once the inflammation has subsided. Depending on the post-operative course, a brief hospital stay may be required.
- Patients with unstable general health: For patients with serious underlying conditions such as heart disease or diabetes, hospitalization for surgery in a more closely monitored environment may be recommended given the surgical risks involved.
- Cysts in challenging locations: When a cyst is located near a joint, or close to important blood vessels or nerves, a more careful approach may be required.
In principle, same-day surgery is possible; however, the final decision is made by the physician based on the patient’s individual cyst condition and medical history.
At the time of consultation, please ask in detail whether same-day surgery is possible and whether hospitalization may be necessary.
💰 How Much Does Surgery for an Epidermoid Cyst (Atheroma) Cost? Health Insurance Coverage
💡 This section explains in detail the cost of epidermoid cyst surgery and health insurance coverage — important information to know before undergoing treatment.
One of the most common questions for those considering surgery for an epidermoid cyst (atheroma) is about cost.
Because epidermoid cyst surgery is generally covered by Japanese public health insurance, the out-of-pocket cost is relatively manageable.
Below is an overview of estimated costs and details regarding insurance coverage.
💴 Estimated Surgery Costs for Epidermoid Cysts (Atheroma)
The cost of surgery for an epidermoid cyst (atheroma) varies depending on the size and location of the cyst, the presence of inflammation, and the surgical technique selected.
In addition, separate fees may apply for the initial consultation, any required tests, anesthesia, and medication.
The following table shows typical estimated costs with health insurance applied (30% patient co-payment).
| Cyst Size / Condition | Estimated Surgery Cost (30% co-payment) | Notes |
| Small (under 3 cm in diameter, no inflammation) | Approx. ¥5,000–¥10,000 | ・Punch excision or small incision is commonly used. ・The lowest-cost scenario. ・Fees for the initial consultation, examination, local anesthesia, prescribed medications (antibiotics, pain relief, etc.), and post-operative wound care may be charged separately. |
| Medium (3 cm to under 5 cm, no inflammation) | Approx. ¥10,000–¥15,000 | ・Excision with fusiform incision is commonly selected. ・Cost is higher than for small cysts due to the wider surgical area. ・Pathological examination fees may be added in some cases. |
| Large (5 cm or more in diameter, no inflammation) | Approx. ¥15,000–¥25,000 | ・Excision with fusiform incision is almost always required. ・Cost is higher due to the increased complexity and time involved. ・Pathological examination fees are almost certain to apply. |
| Inflamed or suppurating cysts | Incision and drainage procedure: Approx. ¥3,000–¥5,000 Definitive surgery (at a later date): The above amount plus the surgery cost for the applicable size |
・When suppuration is present, an initial incision and drainage procedure is performed first. ・This procedure itself carries a cost, and a separate definitive surgery is subsequently required to remove the cyst sac, so total costs tend to be higher. ・In severe cases, the number of follow-up visits may increase, adding to consultation and treatment fees. |
[Important Notes]
・The figures above are estimates only and may vary depending on the medical facility, region, and specific treatment content.
・In most cases, fees for the initial or follow-up consultation, tests (including pathological examination), anesthesia, prescribed medications (antibiotics, pain relief, antiseptics, etc.), and post-operative wound care are charged separately from the surgery fee.
When these are included, the total amount may exceed the estimates above.
・Depending on your health insurance association or local municipality, high-cost medical care benefit systems or medical expense assistance programs may be available — please check whether you are eligible.
・For accurate cost information, we recommend contacting the medical facility you intend to visit directly, or confirming with the physician or reception staff at the time of your consultation.
🏥 Is Surgery for an Epidermoid Cyst Covered by Health Insurance?
To put it simply, surgery for an epidermoid cyst (atheroma) is covered by Japanese public health insurance in most cases.
This is because an epidermoid cyst is medically classified as a “benign skin tumor” that carries a risk of inflammation and infection and is therefore considered a condition requiring treatment.
Patients are therefore able to undergo surgery at the cost corresponding to their applicable co-payment rate (typically 30%, 10%, or 20%).
✅ Cases Covered by Health Insurance:
- 📌 The cyst has grown larger and is interfering with daily life (e.g., rubbing against clothing, causing pain when sitting).
- 📌 The cyst is inflamed or suppurating.
- 📌 Pain or an unpleasant odor is present.
- 📌 Even if the concern is primarily cosmetic, the physician determines that there is a medical necessity for treatment.
❌ Cases That May Not Be Covered by Health Insurance:
- 💅 If a cyst is very small, entirely asymptomatic, and surgery is requested solely for cosmetic reasons despite low medical necessity, it may not be covered by insurance.
In this case, the procedure would be classified as “self-pay” and the full cost would be borne by the patient.
However, because most epidermoid cysts are likely to be considered medically appropriate for treatment given the future risk of inflammation and changes in appearance, cases classified as purely cosmetic in motivation are relatively uncommon.
📝 Pathological Examination:
When surgery is performed under insurance coverage, the excised tissue is typically submitted for pathological examination.
This is an important test to confirm that the cyst is not malignant or some other skin condition.
A formal diagnosis of “epidermoid cyst (atheroma)” is confirmed based on the results of this examination.
🔍 The Importance of Confirming with Your Medical Facility:
Before undergoing surgery, be sure to ask the reception staff or your physician at the medical facility “Will this be covered by health insurance?”
Some cosmetic surgery clinics specialize in self-pay treatment, so it is important to confirm this in advance.
Because leaving an epidermoid cyst (atheroma) untreated can lead to problems such as inflammation and infection, we recommend seeking appropriate treatment under health insurance coverage if you have any concerning symptoms.
🏥 Treatment for Inflamed Epidermoid Cysts
💡 This section explains in detail the specific treatment options for inflamed epidermoid cysts. Understanding what kind of surgery is performed will help you prepare.
What happens when an epidermoid cyst becomes inflamed? How is it treated?
The definitive treatment for an inflamed epidermoid cyst is surgery.
Specifically, there are two surgical approaches: “excision with fusiform incision” and “punch excision (punch-out method)”.
Let us look at each treatment approach in turn.
✂️ (1) Treatment Method: Excision with Fusiform Incision
To prioritize reducing the inflammation first, an “incision and drainage procedure” is performed before surgery.
An “incision and drainage procedure” refers to making a small incision in the skin to drain the pus (incision and drainage).
Once the inflammation has resolved, the surgery to excise the cyst is carried out.
The surgical technique itself is straightforward: the skin is incised in a fusiform (spindle) shape, the cyst is removed, and the wound is sutured closed.
When sutured neatly, the scar tends to become less noticeable over time.
For inflamed epidermoid cysts, this approach tends to result in a better post-operative course than forcing the use of punch excision.
🎯 (2) Treatment Method: Punch Excision (Punch-Out Method)
The punch excision method uses a specialized punch-like instrument to create a small opening in the cyst, through which the cyst contents are squeezed out and the deflated cyst sac is then extracted.
Key features of the punch excision method are generally described as: “minimal scarring and less noticeable results” and “very short procedure time”.
For inflamed epidermoid cysts, same-day day surgery using the punch excision method may also be possible, depending on the physician’s assessment.
→ For more information about epidermoid cyst (atheroma) surgery, please see ‘What Is an Epidermoid Cyst (Atheroma)? A Guide to Receiving Treatment with Confidence.’
💊 Can Medication Treat an Inflamed Epidermoid Cyst?
In the treatment of an inflamed epidermoid cyst, antibiotics may be prescribed to help reduce the inflammation.
Taking antibiotics may relieve the pain, but it is important to understand that this only means the infection causing the pain has settled — it does not mean the cyst itself has been removed.
While this approach can be effective against infection, it is not sufficient on its own as a treatment for the cyst.
To achieve definitive treatment of an epidermoid cyst, surgery is ultimately necessary.
💴 Treatment Costs for Inflamed Epidermoid Cysts
Please be reassured that health insurance applies to the diagnosis, tests, surgery, and pathological examination involved in the treatment of an epidermoid cyst.
The following are approximate treatment costs at IC Clinic.
| Approximate epidermoid cyst surgery costs (30% patient co-payment) | ||
| Exposed area | Under 2 cm | Approx. ¥5,000–¥6,000 |
| 2 cm to under 4 cm | Approx. ¥11,000–¥12,000 | |
| 4 cm or more | Approx. ¥15,000–¥16,000 | |
| Non-exposed area | Under 3 cm | Approx. ¥4,000–¥5,000 |
| 3 cm to under 6 cm | Approx. ¥10,000–¥11,000 | |
| 6 cm or more | Approx. ¥12,000–¥14,000 | |
| ※ As there have been reports of malignant tumors arising from epidermoid cysts, pathological examination is in principle performed at the physician’s discretion. ※ In cases of multiple cysts, it may be possible to operate on adjacent sites simultaneously, subject to the physician’s assessment. ※ In addition to the above surgery fees, separate fees apply for consultation and prescriptions (approx. ¥1,000), tests (approx. ¥1,000), and pathological examination (approx. ¥3,000). |
||
| Approximate epidermoid cyst surgery costs (10% patient co-payment) | ||
| Exposed area | Under 2 cm | Approx. ¥2,000 |
| 2 cm to under 4 cm | Approx. ¥4,000 | |
| 4 cm or more | Approx. ¥5,000 | |
| Non-exposed area | Under 3 cm | Approx. ¥1,500 |
| 3 cm to under 6 cm | Approx. ¥3,500 | |
| 6 cm or more | Approx. ¥4,500 | |
| ※ From October 1, 2022, patients aged 75 and over with a certain level of income will have their patient co-payment rate changed. ※ As there have been reports of malignant tumors arising from epidermoid cysts, pathological examination is in principle performed at the physician’s discretion. ※ In cases of multiple cysts, it may be possible to operate on adjacent sites simultaneously, subject to the physician’s assessment. ※ In addition to the above surgery fees, separate fees apply for consultation and prescriptions (approx. ¥300), tests (approx. ¥300), and pathological examination (approx. ¥1,000). |
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👨⚕️ Treatment Trends at Our Clinic [Physician’s Comment]
From Dr. Kota Takakuwa (Supervising Physician at our clinic)
At our clinic, patients with inflamed epidermoid cysts tend to increase by approximately 20% during seasonal transitions. Inflammation is particularly prone to worsening during periods of increased perspiration or when friction from clothing increases. Because early consultation allows us to offer less invasive treatment options, we encourage patients to come in as soon as they notice redness or pain.
❓ Frequently Asked Questions About Inflamed Epidermoid Cysts
💡 Here we have compiled common questions from patients along with answers. We hope this helps address any concerns or uncertainties you may have.
Finally, here are some frequently asked questions about epidermoid cysts. Please feel free to read whichever sections are relevant to you.
Yes, we recommend visiting a clinic even if you have no pain. The cyst has progressed to mild inflammation, and if left unaddressed, the redness is likely to intensify and swelling and pain may develop. If surgery is ultimately required, seeking care early makes it easier to treat with minimal visible scarring. Therefore, if your cyst is red even without pain, please visit a clinic.
Malignant transformation of an epidermoid cyst is extremely rare. There is no way to distinguish a malignant cyst from an ordinary one by symptoms or appearance alone; however, pathological examination of the excised tissue can determine whether the cyst is malignant.
🏥 For Treatment of Inflamed Epidermoid Cysts in Tokyo (Ikebukuro), Please Consult IC Clinic
💡 At our clinic, experienced specialist physicians provide each patient with an individualized treatment approach.
In this article, we have introduced the characteristics, causes, treatment methods, and costs associated with inflamed epidermoid cysts.
Because an inflamed epidermoid cyst represents a worsening of an ordinary cyst, we encourage you to seek definitive surgical treatment as soon as possible.
To help minimize the possibility of scarring after treatment, we strongly encourage you not to leave your condition unaddressed and to come in for a consultation.
At our clinic, we are able to recommend a surgical approach tailored to your condition that aims to minimize discomfort and reduce the risk of noticeable scarring.
If you are troubled by an inflamed epidermoid cyst, please feel free to consult us.
✨ Four Features of IC Clinic
📌 (1) We provide specialist treatment focused on results.
Our specialist physicians, with extensive experience and a strong track record, deliver results-oriented treatment aimed at minimizing the burden on each patient.
👨⚕️ (2) We propose treatment plans tailored to each patient’s condition and wishes.
We listen carefully to each patient’s concerns and worries and provide an optimized treatment plan.
💉 (3) Minimizing discomfort and keeping scarring to a minimum!
From our wide range of treatment options, we select the approach that best reduces discomfort for the patient and minimizes any lasting impact after the procedure.
👥 (4) A clinic where anyone can feel comfortable seeking advice.
Regardless of age or gender, we strive to create a clinic environment where everyone feels at ease consulting us.
📸 Case Introductions
🔍 [Case Introduction] Woman in Her 70s — Inflamed Epidermoid Cyst (Atheroma) Near the Axilla (Updated August 3, 2025)
This patient was a woman in her 70s. She presented to IC Clinic with a large epidermoid cyst near her right axilla that had become red and swollen, with tenderness and discharge of pus. Following examination, a diagnosis of inflamed epidermoid cyst with infection was made. An initial incision and drainage procedure was performed using the “punch excision (punch method)” to allow the inflammation to settle, followed by definitive surgery to excise the cyst sac. The wound is now stable, with no concern of recurrence, and the patient has been able to return to comfortable daily life.
