Breast cancer or not? A pictorial essay on diagnosing plasma cell mastitis

Purpose This aimed to describe ultrasound, mammography, and magnetic resonance imaging (MRI) findings helping in differentiating plasma cell mastitis (PCM) from breast cancer. Background Plasma cell mastitis (PCM) is a rare, benign, chronic inflammatory breast disease that often mimics breast carcinoma clinically and radiologically, posing a significant diagnostic challenge. It typically affects non-lactating women and may present with overlapping features such as a tender mass, nipple retraction, and skin changes. Although histology remains the diagnostic gold standard, familiarity with imaging findings—particularly on ultrasound and MRI—can aid in differentiation and help avoid unnecessary invasive procedures. Findings PCM presents with a range of clinical signs including a retroareolar mass, nipple retraction, discharge, skin thickening, and reactive axillary lymphadenopathy—features that often mimic inflammatory breast carcinoma. Mammography may show asymmetries, skin and nipple changes, and rod-like calcifications, though findings are frequently non-specific. Ultrasound typically reveals hypoechoic, ill-defined lesions with ductal dilatation, increased vascularity, and, in advanced stages, abscesses or fistulas. MRI shows heterogeneous T2 hyperintensity and post-contrast enhancement patterns (Type I or II curves), while DWI demonstrates restricted diffusion with low ADC values. Definitive diagnosis is achieved through ultrasound-guided core needle biopsy, confirming plasma cell-rich periductal inflammation in the absence of malignancy. Conclusions Given its clinical and radiological resemblance to breast cancer, PCM remains a diagnostic challenge. Awareness of its imaging features and histopathological confirmation via biopsy are essential for accurate diagnosis and to avoid unnecessary surgical interventions.