Invasive Lobular Carcinoma of the Breast With Imaging Features Resembling Mucosa-Associated Lymphoid Tissue Lymphoma: A Case Report

Invasive lobular carcinoma (ILC) is a special histologic type of invasive breast carcinoma characterized by diffuse, single-file infiltration of small discohesive cells. We herein report a case in which differentiation between ILC and primary breast malignant lymphoma was particularly challenging. Imaging findings and core needle biopsy suggested difficulty in distinguishing ILC from mucosa-associated lymphoid tissue (MALT) lymphoma, mainly because the lesion demonstrated dense lymphocytic infiltration. Excisional biopsy ultimately confirmed the diagnosis of ILC. This case highlights the diagnostic challenge posed by ILC presenting with atypical imaging features and marked lymphoid infiltration, which can closely mimic lymphoma. Given the substantial differences in treatment strategies between ILC and primary breast lymphoma, accurate diagnosis necessitates careful integration and summation of imaging, pathological, and immunohistochemical data.