Primary Cutaneous Secretory Carcinoma of the Eyelid: A Case Report and Literature Review

Secretory carcinoma is a low-grade malignant neoplasm characterized histologically by microcystic and tubular structures containing intraluminal secretions and molecularly by the frequent presence of an ETV6::NTRK3 fusion. It most commonly arises in the salivary glands and breast, whereas primary cutaneous secretory carcinoma is exceedingly rare. We report a case of secretory carcinoma arising in the skin of the right lower eyelid in an 82-year-old woman. A gradually enlarging nodule had been present for six months. Excision revealed a dermal tumor composed of mildly atypical polygonal cells forming microcystic and tubular structures with intraluminal secretions. The neoplastic cells expressed S100 protein, mammaglobin, MUC1, MUC4, GATA3, SOX10, and pan-TRK. Fluorescence in situ hybridization demonstrated fusion signals consistent with an ETV6::NTRK3 fusion. Taken together, these findings favored a diagnosis of secretory carcinoma rather than other adnexal malignancies, particularly apocrine and sebaceous carcinomas. This case illustrates the value of integrating morphology, immunohistochemistry, and appropriately interpreted molecular testing in the evaluation of rare eyelid adnexal tumors.