Cutaneous adenomyoepithelioma with histopathological heterogeneity: A case report.

Some skin adnexal tumors display both epithelial and myoepithelial cell populations and can be broadly categorized as biphasic tumors. These include apocrine hidrocystoma, mixed tumor, adenomyoepithelioma (AME), and adenoid cystic carcinoma (ACC). Myoepithelioma is the myoepithelial cell-predominant type in this category. Cutaneous AME is exceedingly rare and usually has a benign prognosis, but it is considered to have the potential for local recurrence and metastasis. We report the case of a 57-year-old man with a 1-year history of an ulcerated nodule on his scalp. Microscopically, it was a defined cutaneous nodule with a focal lobulated architecture, composed of epithelial cells forming ducts and myoepithelial cells distributed around the ducts. In addition to these findings of typical AME, the present case focally revealed atypical features, such as increased mitotic activity (7/10 high power fields), invasive growth, and necrosis. However, cytological atypia was not significant. We conclusively diagnosed cutaneous AME with atypical features, suggesting malignant potential. Moreover, areas showing appearances similar to apocrine hidrocystoma, mixed tumor, myoepithelioma, and ACC were focally observed. We present a unique case of cutaneous AME exhibiting histopathological heterogeneity. The recognition of morphological variation could be helpful in appropriately diagnosing and treating AME of the skin.