Eccrine spiradenoma: clinical and pathologic study of 49 tumors. 
A clinical and pathologic study of 49 eccrine spiradenomas occurring in 46 patients is presented.  The study showed that pain and/or tenderness are not such characteristic clinical features of this tumor as has previously been suggested; either or both were present in only 23% of the 35 patients with well-documented clinical histories.  Some pathologic features, not previously documented in this tumor, were seen and included: cylindromatous foci, aggregates of stromal clear cells, clear cells lining ducts and ulceration of the overlying epidermis.  Two tumors had undergone malignant transformation, but there were no recurrences in the 35 patients with adequate follow-up.