A 79-year-old woman arrives at the clinic complaining of bleeding from an ulcerative lesion on her right breast. The itching lesion has been there for several months and is gradually growing in size. The examination reveals a crusty, thickened, erythematous, and ulcerated nodule with hyperpigmentation. The changes have spread to the adjacent areola. Excisional biopsy revealed clusters of big, polygonal, pleomorphic cells with significant mitotic activity and surrounding necrosis. The stains S-100 and HMB-45 are diffusely positive. Which of the following is the most likely diagnosis?

Question

Quizplus · Accepted Answer

Eductional Objective: On the nipple and areola of his elderly patient is a crusty, ulcerated, hyperpigmented lump. Paget disease of the breast , an adenocarcinoma of the areolar epithelium, was biopsied to distinguish it from nodular malignant melanoma. Histopathology demonstrated that the cells were poorly differentiated, with extensive mitotic activity and necrosis. Following immunostaining, S-100 (a protein produced in neural crest cells such as melanocytes) and HMB-45 (a monoclonal antibody that binds to immature melanosomes present in melanocytic tumors) were positive, confirming melanoma.
Immunostaining is frequently used to aid in the diagnosis of melanoma since histopathologic characteristics are not always enough to confirm the diagnosis. Melanoma is quite likely when tumor cells stain positive for several melanocyte markers (as in this example). 
 S-100 is positive in >95% of melanoma tumors, and HMB-45 is both highly sensitive (>95%) and highly specific (~100%) for the malignancy.

A 79-Year-Old Woman Arrives at the Clinic Complaining of Bleeding