Sebaceous Gland Carcinoma

Sebaceous Gland Carcinoma

Sebaceous gland carcinoma (SGC) is the third most common eyelid malignancy in Western populations and the second most common in Asian populations. It arises from meibomian glands (tarsal plate), glands of Zeis (lash follicles), or sebaceous glands of the caruncle. The upper eyelid is involved twice as often as the lower eyelid — reflecting the greater number and size of meibomian glands in the upper tarsus.

SGC is notorious for masquerading as benign conditions. The most common mimics are:

• Recurrent chalazion — most dangerous masquerade; any chalazion recurring after proper I&C should be biopsied
• Chronic blepharitis or meibomian gland dysfunction
• Unilateral conjunctivitis that fails antibiotic treatment

A key feature distinguishing SGC from BCC is its ability to spread intraepithelially (pagetoid spread) throughout the conjunctival epithelium and skin without forming a discrete mass, making clinical margins unreliable. This also explains why it can present as chronic, diffuse eyelid erythema with madarosis (lash loss) — a presentation easily attributed to blepharitis for months or years.

Diagnosis: Full-thickness eyelid biopsy (including conjunctiva) and map biopsies of the conjunctiva to assess the extent of pagetoid spread. Immunohistochemistry (EMA, adipophilin, androgen receptor) confirms sebaceous differentiation. SGC is associated with Muir-Torre syndrome (MLH1 or MSH2 germline mutations) — microsatellite instability testing and oncology referral are appropriate, especially in patients under 60.

Treatment: Wide local excision with frozen-section control of all margins, including conjunctival margins if pagetoid spread is present. Sentinel lymph node biopsy is appropriate. Exenteration may be required for orbital invasion or extensive pagetoid spread. Adjuvant radiation is used for positive margins or regional nodal disease. The 5-year disease-specific mortality is ~10–20%.