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?
Sebaceous carcinoma is a rare aggressive skin cancer. Sebaceous carcinoma is sometimes called sebaceous gland adenocarcinoma.
Who gets sebaceous carcinoma?
Ocular sebaceous carcinomas affects adults. It occurs more frequently in Asian populations than Caucasians, and is more common in women than in men, particularly those around 60 to 80 years of age. In patients with a predisposing genetic syndrome, it may be diagnosed at a younger age.
Extraocular sebaceous carcinomas occur mainly in older adults and without predilection for male or female.
What causes sebaceous carcinoma?
The exact cause of sebaceous carcinoma is unclear. The following have been reported to possibly increase the risk of these tumours:
- Underlying Muir-Torre or Lynch syndrome
- Previous radiation therapy to the area for a variety of benign and malignant conditions, such as retinoblastoma
- History of oral thiazide diuretic use
- Mutations to the tumour suppressor gene p53
What are the 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 2–3 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 (madarosis), 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.
How is sebaceous carcinoma diagnosed?
Sebaceous carcinoma may be suspected clinically. Definitive diagnosis is based upon patient history, adequate surgical biopsy and the combined knowledge of a pathologist, ophthalmologist and dermatologist.
What is the differential diagnosis of sebaceous carcinoma?
The 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 mimic the condition.
Note that basal cell carcinoma is less aggressive than sebaceous carcinoma, but sometimes shows sebaceous differentiation.
Conditions/diseases that mimic ocular sebaceous carcinoma
- Hordeolum (stye)
- Blepharoconjunctivitis / blepharitis
- Papillary conjunctivitis
- Pyogenic granuloma / reactive haemangioma
- Ocular cicatricial pemphigoid
- Granulomatous inflammation from syphilis or tuberculosis (TB)
- Exophthalmos, often due to Grave disease
- Central retinal artery occlusion causing proptosis
- Torre-Muir syndrome
Other eyelid tumours
- Basal cell carcinoma
- Squamous cell carcinoma
- Cutaneous horn
- Conjunctival carcinoma
- Merkel cell carcinoma
- Benign hair follicle tumours such as sebaceous hyperplasia and sebaceous adenoma.
- Benign sweat gland lesions
- Metastatic tumours
What are the complications of sebaceous carcinoma?
Sebaceous carcinoma, although rare, is an aggressive and potentially dangerous tumour that can lead to significant morbidity and mortality. The overall mortality rate is 5–10% because of inherent tumour factors, or delayed diagnosis and treatment.
Factors for a poorer prognosis include delay in diagnosis of greater than 6 months, tumour diameter greater than 1 cm, and both upper and lower eyelid involvement.
How is sebaceous carcinoma treated?
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.