Sebaceous carcinomas are rare and aggressive carcinomas (cancer arising from tissues that line organs) that affect develop in the skin. More specifically, they develop in sebaceous glands attached to hair follicles in the skin. These glands produce the natural oils in the skin, mainly a substance called sebum. Sebum is a group of complex oils that lubricates the skin in order to protect the skin from friction, as well as acting as a waterproofing mechanism.
Sebaceous carcinomas are more common in women, and are generally diagnosed in people over 60 years old. However, anyone can develop this disease.
Types of Sebaceous Carcinomas
There are two primary types of sebaceous carcinomas, which are categorised by the areas of the body that they develop from.
Periocular Sebaceous Carcinomas
Periocular sebaceous carcinomas are the most common subtype of sebaceous carcinomas, and are generally found around the eyes. More specifically, they develop in the meibomian glands in the eyelids, which are responsible for secreting the lipid layer that prevents tears from drying out on the ocular surface. While this type of cancer can be aggressive, it can have a good prognosis when caught early.
Extraocular Sebaceous Carcinomas
Extraocular sebaceous carcinomas are less common, and develop outside of the eye area. Generally, they can be found in the head and neck, but they have also been found in other areas such as the genitals, ear canal, breasts, trunk, and oral cavity. While this type of cancer can be aggressive, it can have a good prognosis when caught early.
Treatment
If sebaceous carcinoma is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumour) indicates the size and depth of the tumour.
- N (nodes) indicates whether the cancer has spread to nearby lymph nodes.
- M (metastasis) indicates whether the cancer has spread to other parts of the body.
This system can also be used in combination with a numerical value, from stage 0-IV:
- Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissue.
- Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
- Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localised cancer.
- Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
- Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advanced or metastatic cancer.
Cancers can also be graded based on the rate of growth and how likely they are to spread:
- Grade I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
- Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
- Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.
Once your tumour has been staged and graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, stage of disease and overall health.
Treatment options for sebaceous carcinomas may include:
- Surgery, potentially including:
- Mohs micrographic surgery (specialised surgery that removes thin layers of cancer in stages until completely removed; this option is particularly useful in smaller areas, such as the eyelid).
- Wide local excision.
- Lymphonodectomy (removal of affected lymph nodes).
- Enucleation (complete removal of eye; only in rare and extreme cases).
- Radiation therapy.
- Clinical trials.
- Palliative care.
For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.
Risk factors
While the cause of sebaceous carcinomas remains unknown, the following factors may increase the risk of developing the disease:
- Having non-cancerous lumps (also known as benign adenomas) in the sebaceous glands.
- Prior exposure to radiation.
- Having certain conditions, such as:
- Muir Torré syndrome.
- Lynch syndrome.
- Being immunocompromised.
- Prior history of oral thiazide diuretic use.
- Genetic mutations to the p53 tumour suppressor gene.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Early symptoms
The symptoms of sebaceous carcinomas often vary by subtype.
Symptoms of Periocular Sebaceous Carcinomas
Symptoms of periocular sebaceous carcinomas may include:
- Painless, rounded nodule on the eyelid.
- Inflammation and/or pain in the affected area.
- Red or yellowish nodule.
- Nodule that oozes blood.
Symptoms of Extraocular Sebaceous Carcinomas
Symptoms of extraocular sebaceous carcinomas may include:
- Yellowish-tan coloured nodule.
- Ulcerated nodule.
Not everyone with the symptoms above will have cancer, but see your GP if you are concerned.
Diagnosis/diagnosing
If your doctor suspects you have a sebaceous carcinoma, they will order a range of diagnostic tests to confirm the diagnosis, and refer you to a specialist for treatment.
Physical examination
Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities.
Imaging & blood tests
The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), x-ray, and/or ultrasound, depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.
Eye tests
Your doctor may request a variety of eye tests to check for abnormalities in your eye. One of these tests is called an ophthalmoscopy (fundoscopy), which involves using eye drops to widen your pupil and then looking into a large microscope. This option is beneficial as you may not require a biopsy after this test.
Biopsy
Once the location(s) of the cancer has been identified, the doctor will perform a biopsy to remove a section of tissue using a needle. This can be done by either a punch biopsy, a fine needle aspiration, and/or a lymph node biopsy. The samples are then analysed for cancer cells.
Prognosis (Certain factors affect the prognosis and treatment options)
While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on stage, rate/depth of tumour growth, susceptibility to treatment, age, overall fitness and medical history. Generally, early-stage sebaceous carcinomas have a good prognosis and survival rates. However, if the cancer is advanced and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence.
References
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.