Eccrine porocarcinoma arising in a long-standing gluteal lesion with lymph node metastasis: a clinicopathologic case report

Eccrine porocarcinoma (EPC) is a rare malignant adnexal neoplasm that may arise de novo or from a pre-existing poroma. Because of its rarity and overlapping clinical and histopathologic features with other cutaneous lesions, accurate diagnosis may be challenging. We report a 60-year-old man with a 15-year history of a slowly enlarging gluteal lesion that had been repeatedly treated as an inflammatory process. Histopathologic examination following complete excision revealed an infiltrative dermal neoplasm composed of atypical poroid cells arranged in interanastomosing nests with unequivocal ductal differentiation and focal luminal cuticle formation. Adjacent poroma-like areas supported malignant transformation. Immunohistochemically, the tumor showed diffuse CK19, CK7, EMA, and CD117 expression, focal luminal CEA staining, peripheral/basal p63 expression, CK5/6 positivity limited to areas of squamous differentiation, absence of BerEP4 expression, and a Ki-67 proliferation index of approximately 70%. Following positive surgical margins, wide local re-excision and inguinal lymph node dissection revealed a 1.3-cm metastatic deposit in one lymph node without extranodal extension. This case highlights the importance of recognizing eccrine porocarcinoma in long-standing cutaneous lesions with atypical clinical behavior. Because both the clinical presentation and histopathologic appearance may be misleading, accurate diagnosis relies on careful evaluation of characteristic ductal differentiation supported by an appropriate immunohistochemical panel. Early recognition is crucial to avoid diagnostic delay and ensure appropriate surgical management.