Answer: C

Histologic Description: This is a sclerotic lesion which ulcerates the epidermis of the nipple, which accounts for the erosion and eczematous appearance seen clinically. The neoplasm has features of a sclerotic papilloma with florid usual duct hyperplasia. The proliferating epithelial cells are unevenly placed, have hypochromatic nuclei and indistinct cell membranes. Focally one sees punctate central necrosis which is typical of benign sclerotic lesions in the breast. These are the typical features of a nipple duct adenoma.

Differential Diagnosis: Invasive ductal carcinoma would demonstrate a more irregular growth pattern, and absence of myoepithelial cells. Myoepithelial cells were retained in the nipple duct adenoma. Low grade adenosquamous carcinoma may arise in association with papillomas of the breast; however, this is typically an infiltrative lesion demonstrating both glandular and squamous differentiation. Sclerosing adenosis is a lobulocentric process, but lacks a papillary component and is centrally composed of spindled myoepithelial cells with abundant cytoplasm.

Nipple duct adenomas are benign lesions that are generally treated by conservative excision.