Solitary mastocytoma in the eyelid of an adult.

Purpose: To describe the ophthalmic symptoms and histopathological findings in a rare case of an eyelid mastocytoma in an adult.

Observations: A man in his early 60s developed a painless, non-tender, non-pruritic, mobile nodule on the right lower eyelid beneath the inferior orbital rim. The lesion grew to 15 × 9 mm over eleven months. Biopsy revealed a diffuse infiltrate of histiocytoid and spindle-shaped mast cells forming cords and small nests between collagen fibers in the superficial and deep dermis. Mast cell lineage was confirmed by immunohistochemistry. Physical examination revealed no other cutaneous lesions and no evidence of systemic disease. Serum tryptase level was normal. Annual full-body examination by a dermatologist for 4.5 years has revealed neither recurrence in the eyelid nor cutaneous involvement at other sites.

Conclusions and importance: Mast cell tumors limited to the human eyelid are extremely uncommon with only four previously reported cases, including one in an adult. This case highlights the rare possibility of a solitary mastocytoma presenting in the eyelid of an adult.