A Recurrent Case of Papillary Eccrine Adenoma.

Papillary eccrine adenoma (PEA) is a rare benign eccrine gland neoplasm presenting as a solitary nodule, primarily in middle-aged African American females. Accurate histological diagnosis is crucial due to its potential to mimic adnexal carcinomas. Complete excision is recommended due to its risk of local aggression and recurrence. A 75-year-old Caucasian male with a history of basal cell carcinoma (BCC) presented with a recurrent pink, scaly nodule on the right medial pretibial leg area. Initial biopsy showed benign PEA. The lesion recurred after one year, and a re-biopsy confirmed a tubulopapillary adenoma within a scar. The lesion was excised with a 2 mm margin. PEA is characterized histologically by dilated ducts lined by a dual layer of tumor cells, often with intraluminal papillae structures. Immunohistochemical staining aids diagnosis, with markers such as S-100, carcinoembryonic antigen (CEA), and epithelial membrane antigen (EMA) indicating eccrine differentiation. Differential diagnoses include adnexal carcinomas and BCC with eccrine differentiation. Complete excision is necessary to prevent recurrence.