Not All Cases of Mammary Paget’s Disease are Cytokeratin-7 Positive: A Challenging Diagnosis!

Abstract

Mammary Paget’s disease accounts for 1% to 3% of all breast tumors and manifests as a chronic eczematous lesion of the areolar skin. It can occur without any underlying neoplasia or can be present in association with an underlying invasive and/or in situ carcinoma of the breast. The present report describes a challenging nipple punch biopsy showing an infiltration of the lower third to two-thirds of the epidermis by large, ovoid, neoplastic cells. The morphology was consistent with mammary Paget's disease, although immunohistochemistry for cytokeratin-7 (CK7) was repeatedly negative. This resulted in an initial misdiagnosis and, subsequently, a delay in the patient's follow-up. Additional immunohistochemistry for GATA binding protein 3 (GATA3) and human epidermal growth factor receptor 2 (HER2), as well as a second opinion of a breast pathologist, resulted in the diagnosis of mammary Paget's disease. The aim of this article is to raise awareness among pathologists and prevent them from misdiagnosing CK7-negative Paget disease of the breast.

Immunohistochemical expression of TRPS1 in mammary Paget disease, extramammary Paget disease, and their close histopathologic mimics

“…The same is also true for SCCIS. For instance, MPDs may rarely lack CK7 expression,8,9 and SCCISs, particularly those with a pagetoid pattern of growth, can also often express CK7 and Cam5.2 10. Based on our findings, TRPS1 IHC may have some diagnostic utility in the evaluation of pagetoid intraepidermal neoplasms, particularly those arising in the nipple such as MPDs.…”