Abstract
Porocarcinoma is a rare eccrine carcinoma with recurrent and metastatic potential. It commonly occurs in elderly patients with a predilection for the lower extremities and head and neck. Various histopathological features contribute to challenges in making diagnoses. Here we report a case of porocarcinoma mimicking squamous cell carcinoma which had local recurrence and regional nodal metastases after initial excision followed by radiation treatment. A 77-year-old Caucasian male initially presented with a telangiectatic painless nodule on the right ear helix, diagnosed as porocarcinoma, and underwent excision followed by 12-month radiation treatment. Two years later, an intermittently bleeding mass was found on the right posterior ear. Clinical examination showed a 3.5 x 1.8 cm ulcerated mass with bleeding. A shave biopsy demonstrated infiltrative nests and cords of high-grade epithelioid cells with prominent squamous differentiation in a background of solar elastosis, mimicking squamous cell carcinoma. However, presence of scattered ductal structures and immunoprofile of positivity for pancytokeratin, p63, EMA and CEA (patchy) supported a diagnosis of recurrent porocarcinoma. CT confirmed a right external ear mass and right retroauricular and intraparotid adenopathy without evidence of distant metastases. Subsequently, right partial auriculectomy with parotidectomy and neck dissection were performed. Microscopically, tumor showed similar histopathological features with numerous mitosis, necrosis and lymphovascular invasion. Right retroauricular and intraparotid lymph nodes were positive for metastases. During two-year follow-ups, there has been no recurrence. Our report emphasizes the importance of distinction of porocarcinoma from its mimics and necessity of appropriate follow-up intervals and adequate surgical resection to improve prognosis.