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Case Reports

Abstract

Spiradenocarcinoma (SC) is a rare malignant adnexal tumor with sweat gland differentiation and usually arises in a long-standing spiradenoma. Here, we present an extraordinary case of SC with sarcomatoid differentiation that developed distant metastases. A 74-year-old man with a previous history of myxoinflammatory fibroblastic sarcoma presented clinically with a 9 cm asymptomatic skin-colored nodule on his right lower leg for 15 years, which slowly increased in size. An excision was performed, and the sections revealed irregular proliferation composed of atypical epithelial cells in poorly formed glandular structures and with nuclear atypia, increased mitotic rate, and necrosis in the background of spiradenoma, features of SC arising in a spiradenoma. In addition, in some areas, admixed atypical epithelioid spindle cells in poorly formed fascicles infiltrate into the surrounding dermis and subcutaneous tissue. In an immunohistochemical study, both atypical glandular epithelial cells and spindle cells were positive for CAM5.2, and the atypical spindle cells were focally positive for p63 and SMA. Meanwhile, a previous epidural biopsy specimen was retrieved and reviewed. The histopathologic features were similar to those of the sarcomatoid component in the current specimen, and it was regarded as a metastasis. To our knowledge, a SC with sarcomatoid differentiation and distant metastasis has yet to be reported in the medical literature. We present this case to emphasize the aggressive behavior and the risk of distant metastasis of SC with sarcomatoid differentiation and highlight the need to identify any sarcomatoid component when SC is evaluated histopathologically.