Sebaceous gland carcinoma (SGC) is a rare and aggressive skin cancer that originates in sebaceous glands, which produce the skin’s natural oils. These glands are present across most of the body, allowing SGC to develop in various locations. SGC is considered uncommon, representing a small percentage of all skin cancers.
Symptoms and Common Locations
Sebaceous gland carcinoma often appears as a firm, painless lump or nodule that may be yellowish or reddish. These lesions can sometimes bleed or ulcerate. The most frequent site for SGC is around the eye, particularly the upper eyelid, accounting for about 75% of cases. This specific location often leads to misdiagnosis, as SGC can resemble benign inflammatory conditions such as a persistent chalazion or chronic blepharitis. The misdiagnosis can result in a delay of one to three years before correct identification.
While the periocular region is the predominant site, SGC can also form in sebaceous glands elsewhere on the body, often found on the head, neck, trunk, or genital area. These extraocular lesions might present as a slowly growing pink or yellowish lump that could bleed.
Causes and Associated Risk Factors
The precise cause of sebaceous gland carcinoma is often not known. However, several factors increase the likelihood of developing this cancer. Older age is a significant risk factor, with the disease more commonly affecting individuals in their 60s and 70s, and it is more prevalent in women for periocular cases.
Radiation therapy to a specific area can also elevate the risk of SGC developing in that region. A weakened immune system, such as in individuals who have undergone organ transplantation, is another contributing factor.
A notable connection exists with Muir-Torre syndrome, a rare genetic disorder. This syndrome predisposes individuals to sebaceous tumors, including SGC, and various internal cancers, often affecting the gastrointestinal tract. The appearance of SGC can sometimes be the first indication of Muir-Torre syndrome, prompting further genetic evaluation for associated visceral malignancies.
The Diagnostic Process
A definitive diagnosis of sebaceous gland carcinoma primarily relies on a skin biopsy. During this procedure, a doctor removes a tissue sample, which is then sent to a laboratory for examination by a pathologist. The pathologist analyzes the cells under a microscope to confirm the presence of carcinoma and distinguish SGC from other common skin cancers like basal cell or squamous cell carcinoma.
In cases where the lesion appears diffuse or there is concern about spread to lymph nodes, imaging tests may be performed. These can include X-rays, ultrasound, CT, or PET-CT scans to assess whether the cancer has spread beyond the initial site. However, the microscopic analysis of the biopsy specimen remains the most important step in establishing a precise diagnosis.
Treatment Approaches
Surgical removal is the primary treatment for localized sebaceous gland carcinoma, aiming to eliminate all cancer cells along with a margin of healthy surrounding tissue. Mohs micrographic surgery is often the preferred method, particularly for SGC on the face and eyelids. This specialized technique involves removing the tumor layer by layer, with each layer immediately examined under a microscope to ensure all cancer cells have been excised. This process maximizes the preservation of healthy tissue while achieving complete tumor removal, which is especially beneficial in cosmetically sensitive areas.
Another surgical approach is wide local excision, where the surgeon removes the tumor with a predefined margin of healthy tissue. Radiation therapy serves as an additional treatment option, often used after surgery to target any remaining cancer cells, a practice known as adjuvant treatment. It may also be considered as the sole treatment for patients who are not suitable for surgery. Systemic treatments, such as chemotherapy, are generally reserved for advanced cases where the cancer has spread to distant parts of the body.
Prognosis and Long-Term Management
The outlook for individuals with sebaceous gland carcinoma is influenced by several factors, including the tumor’s size, its specific location, and whether it has spread at the time of diagnosis. SGC is considered an aggressive tumor, carrying a notable risk of local recurrence and metastasis to other parts of the body such as lymph nodes, lungs, liver, or bones. The rate of local recurrence can be substantial, with some studies reporting rates as high as 40% for eyelid SGC.
Due to the possibility of recurrence and metastasis, long-term, regular follow-up appointments with a dermatologist or oncologist are highly recommended. These check-ups are important for monitoring for any signs of the cancer returning, with a median time to recurrence often around 14 to 19 months. Full-body skin examinations are also performed during these visits to detect any new cancers, especially given the association with conditions like Muir-Torre syndrome.