Eccrine spiradenoma. An electron microscopic study.

Electron-microscopic studies of two typical lesions of eccrine spiradenoma were performed to correlate ultrastructure and histopathology. The salient ultramorphological features of the parenchyma were an adenoid cystic organization composed of epithelial, myoepithelial, and nonepithelial cell types, and the presence of intracytoplasmic luminae within the epithelial cells. There were no indications that the parenchyma was secretorily active. The stroma ramified through the parenchyma, occupying extensive areas and forming tenuous septa of the loose connective tissue in which blood vessels and nerve fibers were embedded. Profiles of cystoid spaces resulting from invagination of stroma into the parenchyma were frequently encountered. Based on our observations, eccrine spiradenoma appears to differentiate toward ductal structures of eccrine sweat apparatus.