Cystic neutrophilic granulomatous mastitis during chemotherapy treatment for invasive breast carcinoma \u2013 a rare lesion that simulates tumor progression

Abstract

BackgroundCystic neutrophilic granulomatous mastitis (CNGM) is an uncommon and recently described pattern of granulomatous mastitis. To our knowledge, no cases have been described during chemotherapy for invasive breast cancer.Case presentationA 42-year-old female patient had a diagnosis of invasive breast carcinoma (3-cm nodule). During neoadjuvant chemotherapy, she presented with an enlargement of the breast nodule that measured 7.0-cm on palpation. The lesion did not show typical inflammatory clinical findings and simulated tumor progression. A core biopsy showed granulomas with pseudocystic spaces with gram-positive bacilli (Corynebacterium sp.), and numerous circumjacent neutrophils. She was treated with antibiotics and resumed chemotherapy. Surgical specimen showed a 1.0-cm residual carcinoma and extensive xanthogranulomatous inflammation with no evidence of residual CNGM.ConclusionCNGM is usually associated with typical clinical presentation of mastitis. It is an important pattern of granulomatous inflammation to be recognized in the breast since it directly impacts treatment. The present case highlights its potential occurrence during chemotherapy treatment of breast cancer mimicking progression of breast malignancy.