Malignant eccrine spiradenoma. A clinicopathologic study

Malignant eccrine spiradenomas (MES) are exceedingly rare and their immunohistochemical and ultrastructural features have not been fully characterized. We studied two cases, one of them immunohistochemically and electron microscopically. Patient 1 had a 25-year history of multiple exophytic tumors involving the scalp, the skin of the face, and the torso. Of the lesions removed, ten were spiradenomas, two with malignant changes, and three were cylindromas. The malignant areas showed loss of tubular and nesting patterns, lack of two cell populations, and contained anaplastic cells with high mitotic rate. The immunohistochemical findings were consistent with eccrine differentiation. Patient 2 had a cystlike mass of long duration in the right groin. Histologically, the mass consisted of nodules of benign eccrine spiradenomas adjacent to a ductal-cystic mass lined by anaplastic cells, but areas of squamous and glandular differentiation were also present.

(a) Case 1 is probably the first reported MES associated with multiple spiradenomas and cylindromas. (b) Cytodifferentiation in MES is variable, sometimes with almost complete loss of eccrine differentiation. (c) Identification of adjacent spiradenomas may be required for definite diagnosis of MES. (d) Clinical history of longstanding lesions with recent fast growth warrants tissue diagnosis.