Malignant eccrine poroma with multiple visceral metastases: report of a case with autopsy findings.

An autopsy case of malignant eccrine poroma (MEP) with multiple visceral metastases is reported. A flat, dark tumor of 1 cm in diameter developed on a pre-existing pigmented spot at the left side of the waist of a 58-year-old male. The histopathology suggested the tumor to be malignant melanoma. Nine years later, a painless swelling occurred in the left lower leg, resulting from the obstruction of lymphatics at the left inguinal region. The swelling continued and spread with pain, reaching the inguinal region. Two years later, several papules appeared around the left knee, from which an extensive lymphorrhea occurred. The histopathology of the resected papules suggested epidermoid carcinoma or trichilemmal carcinoma, mainly localized within the lymphatics of the upper dermis. Re-examination of the first skin tumor and electron microscopy of the tumor obtained at autopsy revealed that both tumors were MEP. Although the metastases to the local cutaneous regions and lymph nodes via the lymphatics occur in 20% of MEP, cases with multiple visceral metastases are very few.