A rare case of perianal apocrine adenocarcinoma

Apocrine adenocarcinoma is a rare primary cutaneous malignancy that arises from areas with high apocrine gland density, most frequently described in the axilla. There have only been three previously reported cases of apocrine adenocarcinoma in the anal/perianal region. A 72-year-old female presented for evaluation of a perianal lesion with persistent drainage that she had noticed for over a year. The patient proceeded with surgical excision of the perianal nodule. Diagnosis was made based on pathology demonstrating areas of mixed solid and trabecular areas with large nuclei and many prominent mitotic figures, which stained positive for periodic acid-Schiff-diastase, cytokeratin 7 and gross cystic disease fluid protein 15. We are reporting just the fourth such case of apocrine adenocarcinoma in the anal/perianal region. It is important to consider apocrine adenocarcinoma in our differential, because though apocrine adenocarcinoma has a benign clinical presentation, it can have a high incidence of lymph invasion on presentation.