Porocarcinoma detected by fine needle aspiration biopsy of a node metastasis. A case report.

Porocarcinomas were first reported by Pinkus and Meherengan in 1963 as uncommon malignant adnexal tumors of the skin characterized by epidermotropism with pagetoid diffusion within the epidermis. CASE: The cytologic findings of an eccrine porocarcinoma lymph node metastasis in a 65-year-old female and histologic features of the skin recurrence are reported. Metastasis was firstly identified by fine needle aspiration biopsy (FNAB) performed on one inguinal lymph node. Cytologically the tumor was characterized by atypical malignant cells showing clear granular or keratinized cytoplasm and vesicular nuclei, with prominent nucleoli, which were irregularly dispersed or forming nests or cords, sometimes harboring central necrosis. The skin metastasis, detected after the cytologic FNAB diagnosis, showed superficial dissemination within the epidermis and dermal invasion. CONCLUSION: Cytologic diagnosis of porocarcinoma metastases by FNAB is important for adequate treatment, but adherence to strict diagnostic criteria is necessary. The tumor cells could be histogenetically related to the intraepidermal duct cells of the eccrine sweat glands, and pagetoid diffusion is considered a sort of homing phenomenon.