Section Editor: Allison Osmond MD FRCPC
June 10, 2026
Sebaceous carcinoma is an uncommon type of skin cancer. It develops from sebocytes, the cells that make up the oil (sebaceous) glands of the skin. These cells normally produce a fatty substance called sebum, and because the tumor cells continue to make this oily material, the tumor often looks yellow. Sebaceous carcinoma is found most often on the eyelid, where it can be mistaken at first for a harmless lump such as a stye or chalazion, but it can also occur on the rest of the face, scalp, neck, and elsewhere on the skin.
This article explains what a diagnosis of sebaceous carcinoma means, what the findings in your pathology report describe, and how those findings guide the decisions you and your care team will make together. One feature sets this cancer apart from most other skin cancers: in some people it is linked to an inherited condition that also raises the risk of cancers inside the body, so the diagnosis sometimes leads to genetic testing. Most sebaceous carcinomas that are found early and completely removed are treated successfully.
What causes sebaceous carcinoma?
The exact cause of sebaceous carcinoma is not fully understood. Recognized risk factors include previous radiation therapy to the skin, long-term sun exposure, a weakened immune system, and infection with certain viruses such as human papillomavirus (HPV) and HIV.
A particularly important cause is an inherited condition called Muir-Torre syndrome, which is considered a variant of Lynch syndrome. People with this syndrome carry an inherited change in one of the mismatch repair genes (most often a gene called MSH2) that normally help cells fix DNA errors. They tend to develop sebaceous tumors, often more than one and at a younger age, along with an increased risk of cancers inside the body, especially of the colon, uterus (endometrium), and urinary tract. Because a sebaceous carcinoma can be the first sign of this syndrome, the pathologist may perform additional testing on the tumor (described in the biomarker section below), and your doctor may suggest a referral to a genetic counselor, particularly if you are young, have more than one sebaceous tumor, or have a personal or family history of related cancers.
What are the symptoms of sebaceous carcinoma?
Sebaceous carcinoma usually appears as a firm, slowly growing, yellowish lump that is most often painless. On the eyelid it may show up as a thickening of the lid, a persistent lump, or redness and irritation that does not go away, and it can be mistaken for a common eyelid condition such as a chalazion or chronic inflammation. Any lump or eyelid change that does not heal, keeps coming back, or slowly grows should be checked by a doctor.
How is the diagnosis made?
The diagnosis is made after a sample of the tumor is examined under the microscope by a pathologist. The sample is obtained by a biopsy, and the diagnosis may also be made after the whole tumor is removed by an excision. If the diagnosis is made on a small biopsy, your doctor will usually recommend a second procedure to remove the rest of the tumor.
Under the microscope, sebaceous carcinoma is made up of sheets and rounded groups (lobules) of abnormal cells. Many of the cells contain small bubbles in their cytoplasm (the material surrounding the center of the cell), giving them a foamy or bubbly appearance; these bubbles are the droplets of oil the tumor cells produce. The cells often have enlarged, irregular nuclei (the part of the cell that holds the DNA) and frequent mitotic figures (dividing cells), reflecting rapid growth. In some cases, the tumor cells spread upward in a scattered fashion through the surface skin or the lining of the eyelid, a pattern called pagetoid spread, which is important because it can make the true extent of the tumor larger than it appears. Because sebaceous carcinoma can resemble other skin cancers such as basal cell carcinoma and squamous cell carcinoma, the pathologist often uses immunohistochemistry (special stains that detect specific proteins in the cells, such as adipophilin, EMA, and androgen receptor) to confirm that the tumor arises from sebaceous cells. Once the diagnosis is confirmed, imaging may be used to check whether the cancer has spread. Additional testing of the tumor for mismatch repair proteins, which can point to an inherited syndrome, is described in the biomarker section below.
Histologic grade
Sebaceous carcinoma is not given a standard numeric grade. Pathologists may describe the tumor as well differentiated (the cells clearly resemble normal sebaceous cells) or poorly differentiated (the cells look very abnormal and are harder to recognize as sebaceous), which gives a general sense of how the tumor may behave. However, there is no formal grading system for this cancer that directly determines treatment, so your report may not include a grade.
Perineural invasion
Perineural invasion means that tumor cells are seen attached to or growing along a nerve. Nerves run throughout the body and carry signals such as temperature, pressure, and pain. Perineural invasion is important because tumor cells can travel along a nerve into nearby tissue, which makes the tumor harder to remove completely and raises the risk that it will return after treatment. Your report will state whether perineural invasion is present.
Lymphovascular invasion
Lymphovascular invasion means that tumor cells are seen inside a blood vessel or a lymphatic channel. Blood vessels carry blood, while lymphatic channels carry a clear fluid called lymph. These vessels give tumor cells a route to spread to lymph nodes or distant organs, so the presence of lymphovascular invasion is associated with a higher risk of spread. Your report will state whether it was seen.
Surgical margins
A margin is the rim of normal-looking tissue removed around the tumor during surgery. Margins are usually reported only after an excision meant to remove the entire tumor, not after a small diagnostic biopsy.
- Negative margin — No tumor cells are seen at the cut edge, which suggests the tumor was completely removed. The pathologist often records the distance, usually in millimeters, from the nearest tumor cells to the edge, because a wider clear margin is associated with a lower risk of the tumor returning.
- Close margin — Tumor cells are near the cut edge but do not reach it. Depending on the distance, your doctor may discuss further surgery or radiation.
- Positive margin — Tumor cells are present at the cut edge, which means some tumor may remain. A positive margin is associated with a higher risk that the tumor will return at the same site and may lead to further surgery or radiation. Because sebaceous carcinoma can show pagetoid spread, the true edge of the tumor can be hard to judge, which is one reason margins are examined carefully.
Lymph nodes
Lymph nodes are small immune organs found throughout the body. Tumor cells can travel from the skin to nearby lymph nodes through lymphatic channels; when tumor cells are found in a node, this is called a lymph node metastasis. Sebaceous carcinoma can spread to the lymph nodes that drain the area of the tumor. For tumors on or around the eyelid, these are usually the nodes in front of the ear and in the neck. Lymph nodes are generally examined only when they feel enlarged or look suspicious on imaging, although for some higher-risk tumors a sentinel lymph node biopsy (sampling of the first node that drains the area) may be considered. If a node is removed, the report will state how many nodes were examined and how many contain tumor.
Biomarker and molecular testing
Biomarkers are features of the tumor, often proteins or genetic changes, that provide information beyond the diagnosis itself. For sebaceous carcinoma, the most important biomarker test looks at the mismatch repair (MMR) proteins, because the result can reveal an inherited syndrome and may also influence treatment in advanced disease.
The mismatch repair system is a group of proteins (the four most important are MLH1, PMS2, MSH2, and MSH6) that fix small errors when DNA is copied. Pathologists test for these proteins using immunohistochemistry, and the report describes whether each one is still present in the tumor cells. The result is reported in one of two ways:
- Mismatch repair proficient (pMMR) — All four proteins are present. The report may describe this as the proteins being “intact,” “retained,” “preserved,” or showing “no loss of expression.” This is the normal result and means the repair system is working. On DNA-based testing, the matching result is microsatellite stable (MSS). A proficient result makes an inherited syndrome less likely, although it does not completely rule one out, and it means immunotherapy based on mismatch repair status alone is generally not used.
- Mismatch repair deficient (dMMR) — One or more of the proteins are missing. The report will name which ones, for example “loss of MSH2 and MSH6” or “loss of MLH1 and PMS2.” On DNA-based testing, the matching result is microsatellite instability-high (MSI-H). This is the result that carries the added implications described below.
A mismatch repair deficient result matters for two reasons:
- Inherited syndrome — Loss of a mismatch repair protein in a sebaceous tumor raises the possibility of Muir-Torre syndrome and the related Lynch syndrome. A deficient result is a clue, not a diagnosis on its own; confirming the syndrome requires a separate germline genetic test, usually arranged through a genetic counselor, and it has important implications for cancer screening for both the patient and their family members.
- Treatment — Tumors that are mismatch repair deficient may respond to immunotherapy. A drug called pembrolizumab is approved for advanced, mismatch repair-deficient cancers regardless of where in the body the cancer started, so this result can open a treatment option if a sebaceous carcinoma is advanced or has spread.
You can read more in the article on mismatch repair and microsatellite instability across cancer types and in the Biomarkers section of this site.
Pathologic stage (pTNM)
The pathologic stage describes how advanced the cancer is, based on the tissue removed at surgery. Sebaceous carcinoma is staged using the TNM system of the AJCC (American Joint Committee on Cancer), 8th edition. Because most of these tumors occur on the eyelid, a staging system specific to carcinoma of the eyelid is used for tumors in that location, while tumors elsewhere on the skin are staged with the system for skin (cutaneous) carcinomas. In both systems, the tumor stage (pT) is based mainly on the size of the tumor and whether it has grown into deeper structures. Spread to distant organs (the M category) is determined by imaging. Many small tumors that are completely removed are not assigned a formal stage.
The eyelid tumor stages are, in simplified form:
- pT1 — Tumor is 10 mm or smaller.
- pT2 — Tumor is larger than 10 mm but 20 mm or smaller, or it involves the full thickness of the eyelid.
- pT3 — Tumor is larger than 20 mm, or it has grown into nearby structures such as the tear drainage system or the eye socket.
- pT4 — Tumor has grown into deeper structures such as the orbit, the sinuses, or the brain.
The nodal stage describes whether the cancer has reached the lymph nodes:
- pN0 — No tumor is found in the lymph nodes.
- pN1 — Tumor is found in one or more lymph nodes.
- pNX — The lymph nodes could not be assessed.
What is the prognosis?
The outlook for sebaceous carcinoma is generally favorable when the tumor is found early and completely removed. The cancer can come back at the same site, particularly when removal is incomplete, and it can spread to nearby lymph nodes; spread to distant organs is less common. Tumors around the eye have historically been considered higher-risk because of their location and their tendency to show pagetoid spread, which can make complete removal more difficult.
Several features in the pathology report are associated with a higher risk that the cancer will return or spread:
- Large tumor size and deep invasion — Bigger and deeper tumors are harder to remove completely.
- Pagetoid spread — Scattered tumor cells in the surface skin or eyelid lining can extend beyond the visible tumor.
- Positive or close margins — Tumor at or near the cut edge increases the risk of local recurrence.
- Perineural invasion — Tumor growing along nerves is harder to remove and more likely to recur.
- Lymphovascular invasion — Indicates the tumor has reached vessels that can carry cells elsewhere.
- Lymph node involvement — Spread to lymph nodes lowers the chance of cure.
- Poorly differentiated appearance — Tumors whose cells look very abnormal tend to behave less predictably.
What happens after the diagnosis?
Treatment is usually coordinated by a team that may include a dermatologist, an eye surgeon (oculoplastic surgeon) for eyelid tumors, a surgical oncologist, a radiation oncologist, a pathologist, and, when an inherited syndrome is suspected, a genetic counselor. The main treatment for sebaceous carcinoma is complete surgical removal. Because the tumor can spread in a scattered (pagetoid) pattern, the surgeon often aims for a generous margin of normal tissue, and Mohs micrographic surgery, a technique in which the tumor is removed in thin layers that are checked under the microscope during the operation, is frequently used to confirm that all of the tumor has been removed while sparing as much healthy tissue as possible. For eyelid tumors, small samples of the nearby eyelid lining (map biopsies) may be taken to look for pagetoid spread.
Radiation therapy may be considered after surgery when there are high-risk features, such as a positive margin that cannot be removed with more surgery, or as the main treatment for people who are not candidates for surgery. When the cancer has spread to lymph nodes or distant organs, the care team may consider additional treatment, and if the tumor is mismatch repair deficient, immunotherapy may be an option. After treatment, regular skin and eye examinations are important because the cancer can return and because people who have had one skin cancer are at higher risk of developing another. If testing or genetic counseling points to Muir-Torre or Lynch syndrome, your doctor will arrange a personalized screening plan, which often includes regular colonoscopy and other cancer screening, and will discuss testing for family members.
Questions to ask your doctor
- Where was my tumor located, and how large was it?
- Was the whole tumor removed, or were tumor cells found at the margins?
- If the margins were positive, do I need more surgery or radiation?
- Was perineural or lymphovascular invasion seen?
- Was my tumor tested for mismatch repair (MMR) proteins?
- Could I have Muir-Torre or Lynch syndrome, and should I see a genetic counselor?
- Should my family members be tested?
- Do I need a colonoscopy or other cancer screening because of this diagnosis?
- Would Mohs micrographic surgery be a good option, especially for an eyelid tumor?
- Has the cancer spread to my lymph nodes, and do I need a sentinel lymph node biopsy?
- What is the stage of my cancer, and what does that mean for treatment?
- How often will I need follow-up, and what changes should I watch for?
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