What is a sebaceous gland?
Sebaceous glands are small glands connected to hair follicles in the skin. They are located in any hair-bearing region of the body but are most numerous on the skin of the scalp and face. The glands are responsible for producing sebum which is an oily substance that keeps hair and skin moisturized.
What is a sebaceous carcinoma?
Tumours of the sebaceous glands may be benign, such as sebaceous hyperplasia. Sebaceous carcinoma (also called sebaceous carcinoma) is a more dangerous tumour. It is a rare aggressive skin cancer that commonly occurs around the eye region. Sebaceous carcinoma has been reported at other sites less often.
Sebaceous carcinoma is sometimes called sebaceous gland adenocarcinoma, or sebaceous carcinoma.
Clinical features of sebaceous carcinoma
Sebaceous carcinoma most commonly develops from the meibomian glands which are located mostly in the upper but also in the lower eyelids. Clinical features of ocular sebaceous carcinoma include:
- Small, erythematous or yellowish, firm, deep-seated, slowly enlarging nodule on the upper eyelid.
- Lesions occur on the upper eyelid 2 to 3 times more commonly than on the lower eyelid.
- The lesion is often mistaken for chalazion (a benign inflammation of the meibomian gland).
- As the carcinoma grows it may spread onto the conjunctiva, where it can be mistaken for keratoconjunctivitis or blepharoconjunctivitis.
- In advanced cases, spread of the lesion may lead to both upper and lower lid lesions and cause loss of eyelashes, ulceration and distorted vision.
- Undiagnosed or late diagnoses can lead to metastases (spread) to lymph nodes and parotid glands.
Ocular sebaceous carcinoma
Extraocular sebaceous carcinoma accounts for about 25% of sebaceous carcinomas. These tumours mostly occur around the head and the neck. Other sites where these tumours have been found include the genitals, ear canal, breasts, trunk and oral cavity. The clinical presentation of extraocular lesions is non-specific; they typically appear as a pink to yellow-red nodule of varying sizes.
Diagnosis of sebaceous carcinoma
A diagnosis of ocular sebaceous carcinoma is often delayed by months to years (mean delay from disease onset to diagnosis ranges from 1-3 years) because numerous other inflammatory conditions, autoimmune diseases, infectious processes and other tumours clinically mimic the condition. For example, basal cell carcinoma is less aggressive than sebaceous carcinoma, but sometimes shows sebaceous differentiation.
|Differential diagnosis of ocular sebaceous carcinoma|
|Differential conditions/diseases||Differential tumours|
Definitive diagnosis is based upon patient history, adequate surgical biopsy and the combined knowledge of a pathologist, ophthalmologist and dermatologist.
Causes and risk factors for sebaceous carcinoma
The cause of sebaceous carcinoma is still unclear. The following have been reported to possibly increase the risk of these tumours:
- Underlying Muir-Torre syndrome
- Previous radiation therapy to the area for a variety of benign and malignant conditions, e.g. retinoblastoma
- History of oral thiazide diuretic use
- Mutations to the tumour suppressor gene p53
Ocular sebaceous carcinomas occur more frequently in Asian populations and is more common in women, particularly those around 60 to 80 years of age.
Extraocular sebaceous carcinomas occur mainly in older adults and without predilection for male or female.
Complications and treatment of sebaceous carcinoma
Sebaceous carcinoma, although rare, is an aggressive and potentially dangerous tumour that can lead to significant morbidity and mortality. A delay in diagnosis of greater than 6 months, tumour diameter greater than 1cm and both upper and lower eyelid involvement are factors for a poorer prognosis. The overall mortality rate is 5-10% because of mistakes in diagnosis and delay in treatment.
Radical surgical excision with frozen section control by either a standard method or Mohs micrographic surgery is the most common and effective method of treatment. Approximately, 30% of sebaceous carcinomas recur after resection.
Radiation therapy should only be used in patients unable or willing to undergo surgery.