Abstract

Plasma cell mastitis (PCM) is an aseptic inflammatory process of the breast, characterized by lactiferous duct dilatation and plasmacytic inflammatory infiltrate of unknown etiology. PCM occurs in non-pregnant, non-lactating females, has an association with nipple inversion and smoking, and presents as a breast mass with changes to the overlying skin. We report a 71-year-old female former smoker who presented seeking a second opinion for 6 months of skin flaking progressing to ulceration, involving the left areola and peri-areolar skin. An initial biopsy performed at an outside institution had been interpreted as eczema. The lesion did not improve despite multiple topical over-the-counter treatments including topical antibiotic ointments. Examination showed a 6-cm eroded erythematous plaque on the left breast, involving areola and with destruction of the nipple. No masses were palpated. Ultrasound showed scattered subcentimeter hypoechoic areas suggestive of cysts, classified as BIRADS-3. Skin punch biopsy was performed for a clinical concern of Paget disease. Sections revealed vacuolar interface dermatitis with atrophy, mild papillary dermal hyalinization, and robust superficial and deep perivascular lymphoplasmacytic infiltrate. Special stains were negative for fungi and spirochetes. No kappa or lambda light chain restriction or elevated IgG4:IgG was identified by immunohistochemistry. A diagnosis of plasma cell mastitis was rendered. The patient reported improvement with prescription steroids. There is significant clinical and radiographic overlap between PCM, Paget disease, and inflammatory breast carcinoma. Prognosis and management of these entities differ, making definitive diagnosis on histopathology key. Awareness of the dermatopathologic features of PCM is essential for guiding appropriate therapy.

Financial Disclosure:
No current or relevant financial relationships exist.