Understanding the Puzzle of Primary Breast Lymphoma: An Experience in a Tertiary Care Center in North India.

Background Breast carcinoma is the most common cause of death in women arising primarily from either epithelial or stromal components. Primary breast lymphoma (PBL) is a less common type of neoplasm arising from the lymphoid tissue and is classified as non-Hodgkin's lymphoma (NHL). PBL is a rare tumor that accounts for less than 1% of total primary malignant neoplasms of the breast. The majority of PBLs are of B-cell origin; the most common histological type is diffuse large B-cell lymphoma (DLBCL) followed by follicular lymphoma (FL) and other T-cell and B-cell lymphomas. Material and methods We conducted this five-year retrospective descriptive PBL study from July 2019 to May 2024 at a tertiary care center in North India. We included 11 cases of diagnosed PBL based on morphology and confirmation by at least one lymphoid differentiation marker, that is, leukocyte common antigen (LCA) We retrieved paraffin-embedded blocks from the archive and conducted routine hematoxylin and eosin (H&E) staining and Leishman's stain. We applied an extended immunohistochemistry (IHC) panel to confirm the microscopic findings We used the Dako (Agilent Diagnostics & Genomics Group) antibody with a dilution of 1:100.  Results In this study, patients' mean age was 46.8 years (32 to 84 years). Radiological findings indicated that the tumor was indistinguishable from carcinoma. Microscopic findings showed that cells were medium to large lymphoid cells displaying moderate pleomorphism, centrally placed nuclei, vesicular to coarsely clumped chromatin, and scant cytoplasm. IHC showed one case of T-cell origin (ALCL) and 10 of B-cell origin. Among the B-cell cases, four were DLBCL, four were high-grade NHL likely DLBCL and two were high-grade lymphoma. Conclusion Primary breast lymphoma is a rare tumor that closely resembles breast carcinoma clinically as well as radiologically. This study is an effort to highlight the importance of clinical, radiological, and histopathological parameters as well as immunohistochemical features in confirming diagnosis. We also emphasize a treatment protocol and survival outcome in hopes that this knowledge will provide an understanding of early diagnosis and proper management of disease.