Fine needle aspiration cytopathology of eccrine spiradenoma

Eccrine spiradenoma (ES) is a rare benign cutaneous adnexal tumor. The aim of our study was to discuss the clinical presentation, cytomorphologic features, and differential diagnosis of a series of 3 cases of ES diagnosed by fine needle aspiration (FNA).The pathology databases were searched for cases of ES diagnosed by FNA and confirmed by follow-up surgical excision. FNA smears, cell blocks, and histologic sections were examined.Three cases of ES that had presented as a soft tissue mass from 3 patients were reviewed. The sites included the left forearm, left leg, and left ankle. Cytology smears showed the presence of hypercellular 3-dimensional dense cell clusters and smaller loose cell aggregates, single cells, and bare nuclei. Most cells had round to oval nuclei, scant cytoplasm, and indistinct cell borders. A second population of cells had more spindled nuclei and were often dispersed as single cells. Scattered lymphocytes were present. Two cases showed the presence of pseudo-rosettes composed of hyaline globules of basement membrane-like material with a surrounding row of basaloid cells. None of the cases showed cytologic atypia, necrosis, or mitoses. Immunohistochemistry was used in 2 cases and showed positive staining with myoepithelial markers (smooth muscle actin, calponin, S100, and CK5). The cytology diagnoses were ES, basaloid cutaneous adnexal neoplasm, and suspicious for ES.FNA cytopathology of ES demonstrated banal basaloid and spindle cells, lymphocytes, and infrequent metachromatic-stained hyaline globules. A specific diagnosis requires immunohistochemistry testing to avoid confusion with other cutaneous basaloid neoplasms.