Malignant eccrine spiradenoma (Spiradenocarcinoma) - A clinicopathologic study of 12 cases

Malignant eccrine spiradenoma is a very rare tumor. The clinicopathologic f eatures of 12 cases are reported herein. Six patients were men, six were wo men, and the average patient age was 62 years. Seven tumors were located on the trunk, three on the extremities, and two in the head and neck region. All tumors were large (average size-7.5 cm). Lesions had been present from 7 months to 30 years before surgical removal. In all cases, continuity betw een benign eccrine spiradenoma and areas with malignant change was observed . Malignancy was evidenced by increased mitotic rate, necrosis, nuclear aty pia, pleomorphism, and hyperchromasia, loss of nested and trabecular growth patterns, and absence of a dual cell population. In most cases (8 of 12), the malignant component comprised the bulk of the lesion. Two distinctive h istologic patterns were observed. Five of 12 tumors exhibited abrupt transi tion between a benign eccrine spiradenoma and a high-grade carcinoma compon ent. The others lacked a clear-cut transition between benign and malignant components and were diagnostically challenging. Diagnosis in such cases was established based on the loss of two cell populations, increased nuclear t o cytoplasmic ratio, hyperchromasia, and marked mitotic activity. Two tumor s showed focal squamous differentiation. Five of seven patients on whom the re was follow-up information were free of disease (average duration of foll ow-up = 3.4 years). One patient developed metastases to local lymph nodes 5 years after the primary tumor was resected. This patient had no evidence o f disease 16 months after resection of her lymph node metastases.