Paget disease of the nipple is an uncommon manifestation of breast cancer with involvement of the nipple. The disease presents as an eczematous, red, pruritic and/or scaling rash which may be mistaken for eczema. Paget disease occurs due to intraepidermal proliferation of malignant cells from an underlying ductal carcinoma in-situ with extension into the nipple skin via the lactiferous sinuses without breaching the basement membrane.

This slide demonstrates an inflamed and eroded nipple eptithelium with a proliferation of large atypical cells which are more numerous and confluent near the area of erosion. Small clusters and single malignant cells (ie. Pagetoid spread) are also seen within the epithelium further away from the more confluent areas. The large lactiferous ducts underlying the area of Paget disease also show involvement by high grade ductal carcinoma in-situ.

In addition to these classic findings of Paget disease, this case also demonstrates an unusual presentation of invasive ductal carcinoma NOS arising from Paget disease with infiltration of the nipple dermis by a few irregularly shaped clusters of malignant cells which appear to be discontinuous from the overlying Paget disease. Focal lymphovascular invasion is also identified.

The prognosis of Paget disease depends on the features of the underlying carcinoma (if present). The prognosis is excellent if there is only in-situ disease.

This slide shows D2-40 stain. See Related Content for H&E stain.