Abstract
A mammary fibroadenoma with prominent sebaceous gland-like structures in a female Donryu rat aged 67 weeks was immunohistochemically investigated. The tumor demonstrated a mixture of both epithelial and connective tissue components, the former having both single- and multi-layered patterns. Characteristic sebaceous gland-like structures were apparent in connection with multi-layered epithelium. Area of single-layered epithelium comprised well-differentiated myoepithelial cells positive for alpha-smooth muscle actin (alpha-SMA), similar to mammary ducts. In contrast, many epithelial cells on the basal sides of multi-layers were negative for alpha-SMA, but positive for cytokeratin 14 (CK14), suggesting pluripotency. From these results, we diagnosed this case as a mammary fibroadenoma with sebaceous gland metaplasia.
