BACKGROUND: Eccrine porocarcinoma, or malignant eccrine poroma, is a rare primary skin tumor that develops in the sixth and seventh decades of life, and can present as a painless and solitary nodule. Histopathology is required to confirm the diagnosis. A rare case is presented of metastatic eccrine porocarcinoma, occurring four years after surgical excision of the primary scalp tumor, and includes a review of the literature.
CASE REPORT: A 67-year-old man initially presented with a scalp lesion that was non-painful, exophytic, and pigmented. Following complete excision, histopathology confirmed the diagnosis of eccrine porocarcinoma with clear resection margins. Four years later, he presented with discrete erythematous patches and plaques, in a zosteriform distribution, in the skin of the right neck, shoulder, and chest. A biopsy and histopathology of the skin rash confirmed metastatic eccrine porocarcinoma. A positron-emission tomography-computed tomography (PET-CT) scan identified areas of hypermetabolic activity, with a standardized uptake value (SUV) of 12, and an infiltrating soft tissue tumor in the right suboccipital region. Surgical resection of the suboccipital mass, followed by histopathology, confirmed metastatic eccrine porocarcinoma. During a postoperative ear, nose, and throat (ENT) examination, he was found to have metastases in the right ear canal. The patient received five cycles of chemotherapy, but later developed renal failure and eventually chose palliative care.
CONCLUSIONS: A rash-like presentation of skin metastasis to the trunk and metastasis to the ear from a primary eccrine porocarcinoma is rare. Early diagnosis and adequate surgical resection are recommended to reduce patient mortality.

Keywords: Eccrine Porocarcinoma, Head and Neck Neoplasms, Neoplasms, Adnexal and Skin Appendage