Primary cutaneous adenomyoepithelioma.

An 83-year-old Caucasian woman presented to her dermatologist with a 5-cm subcutaneous tumor on her right thigh. The lesion had been present for many years, but had recently enlarged. Incisional biopsy showed a multinodular tumor composed of variably sized glands comprised of a luminal layer of epithelial cells surrounded by one or more layers of myoepithelial cells. The histopathologic features resembled those of adenomyoepithelioma, an uncommon neoplasm usually encountered within the breast. Primary cutaneous adenomyoepithelioma is very rare yet shares histopathologic features with common cutaneous lesions such as spiradenomas and benign mixed tumors (chondroid syringomas). Primary cutaneous adenomyoepithelioma is part of the spectrum of epithelial-myoepithelial tumors that includes benign mixed tumor, myoepithelioma and myoepithelial carcinoma. This rare tumor may mimic malignant lesions including metastatic adenocarcinoma. Like its breast counterpart, primary cutaneous adenomyoepithelioma should probably be regarded as a neoplasm of borderline malignant potential.