Case report: differential diagnosis between primary cutaneous apocrine adenocarcinoma versus extramammary or metastatic breast adenocarcinoma.

Cutaneous apocrine adenocarcinoma (CAA) is a rare adnexal neoplasm that histologically can mimic breast carcinoma metastatic to the skin or apocrine carcinoma arising in ectopic breast tissue. It can present with a wide range of clinical modalities and can often simulate many benign processes, which delays its diagnosis and hinders its prognosis. We describe a case of a 33-year-old man who had a short-evolution small nodule in the right axilla with local lymph node metastases. The immunohistochemical characterization was closer to that of breast adenocarcinoma than to an adnexal neoplasm. This was established as the main differential diagnosis. Diagnosis of cutaneous apocrine adenocarcinoma may be difficult and immunomarkers are not specific. The anatomical criteria and systemic investigation are mandatory to establish the correct diagnosis.