Mammary Paget's Disease

Mammary Paget disease is a rare form of breast cancer, which typically presents as an eczematous plaque on the nipple or surrounding skin. It is often a clinical diagnosis that is confirmed with skin biopsy. Histologic hallmarks of mammary Paget disease include large, pleomorphic, malignant, ductal epithelial cells within the epidermis. Chronic lichenoid inflammation may be seen in the papillary dermis but is not diagnostic. Because mammary Paget disease often overlies ductal carcinoma in situ or invasive carcinoma of the breast, prompt bilateral mammography is warranted. We report a case of Paget disease of the nipple with negative breast imaging that was originally misdiagnosed due to a dense lichenoid infiltrate obscuring the neoplasm.

Primary melanoma of the nipple (PMN) is exceedingly rare, with only single cases reported to date. We identified 10 patients with PMN: 5 females, 5 males, median age 55.5 years (range 29-66) at diagnosis of melanoma in situ (4 cases) or invasive melanoma (6 cases, Breslow depth 0.2 mm to 3.5 mm). Follow-up was available for all 10 patients (median 19 months, range 1-183). Nine patients had no evidence of disease; one patient died of disease (13.5 months) after presenting with a nodal metastasis. One case was exceptional, because the patient presented with a pigmented lesion that histopathologically exhibited co-existence of melanoma in situ and Paget disease, a challenging differential diagnosis due to immunohistochemical pitfalls in distinction between melanoma in situ and the pigmented variant of mammary Paget disease. Here we report the second largest series of PMN including a case of PMN colliding with mammary Paget disease, to raise awareness of these rare malignancies.