Abstract

Introduction: Mammary Paget’s disease is a malignant proliferation of glandular epithelial cells that typically presents as an indolent erythematous, eczematous rash of the areolar skin. Case presentation: Our patient is a 66-year-old Black male with a history of Hepatitis C with sustained virologic response who presented with 6 months of a pruritic, burning left nipple rash. He endorsed no new contactants to the area but does report frequent exercise with rubbing of the nipple against clothing. Of note, he denied a history of atopic dermatitis. On physical examination, he was Fitzpatrick Type VI; his left nipple and areola had a well-demarcated, round, hyperpigmented, lichenified plaque with a central focus of ulceration. The rash did not improve with a two-week course of triamcinolone ointment and barrier protection during exercise. On close follow-up, a punch biopsy of the left nipple was performed and demonstrated a proliferation of atypical epidermal cells with ample cytoplasm. The cells were present in solitary units and aggregates and showed a pagetoid scatter. On immunohistochemical staining, the atypical cells were negative for cytokeratin-7 and MelanA, but positive for GATA-binding protein 3 (GATA3) and Cam5.2. The clinical presentation, atypical pagetoid proliferation, and GATA3 positivity confirmed the diagnosis of Paget’s disease. We placed an urgent referral to the multidisciplinary breast cancer clinic for further evaluation and treatment. Conclusion: We present this unusual case to highlight awareness of the diagnostically problematic entity of cytokeratin-7 negative mammary Paget’s disease and to emphasize the need for a high index of clinical suspicion and histologic correlation. Given most mammary Paget’s cases are associated with underlying high-grade carcinoma in situ or invasive carcinoma, prompt diagnosis and referral to breast oncology are essential.

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