Breast Mass as the Initial Presentation of B-Cell Acute Lymphoblastic Leukemia: A Case Report

Introduction: Breast involvement by acute lymphoblastic leukemia (ALL) is an exceedingly rare clinical entity, often posing a significant diagnostic challenge as it can mimic common benign or malignant breast conditions. Case presentation: A 17-year-old female presented with a palpable right breast mass and axillary lymphadenopathy. Initial imaging and clinical findings were misinterpreted as an infectious or inflammatory process. Her course was complicated by axillary vein thrombosis and a large pleural effusion. Subsequent clinical deterioration prompted a peripheral blood smear and bone marrow biopsy, which revealed B-ALL with 40% blasts, confirmed by immunohistochemistry (positive for LCA, CD20, PAX5, TDT). Despite an initial favorable response to chemotherapy (BFM protocol), a breast biopsy revealed persistent disease. The treatment was escalated to hyper-CVAD, but the patient succumbed to complications, including neutropenic fever, pneumonia, and paraplegia. Conclusion: This case underscores the diagnostic consequence of leukemic breast infiltration. A high index of suspicion for hematological malignancy is essential when evaluating breast masses, particularly in young patients with atypical or rapidly progressing features. Fine-needle aspiration (FNA) coupled with immunophenotyping is a rapid and effective diagnostic tool that can prevent unnecessary surgeries and ensure the initiation of systemic chemotherapy for managing this aggressive disease.