Primary Breast Lymphoma in Mexico: A 15-Year Retrospective Case Series From a Tertiary Center Suggesting a Distinctly Early Age at Presentation

BACKGROUND: Primary breast lymphoma (PBL) is a rare extranodal lymphoma involving breast tissue and most commonly affects women in the sixth to seventh decades of life. We describe a clinicopathological series of PBL cases diagnosed at a tertiary referral center in Mexico. Histologically, most cases correspond to B-cell non-Hodgkin lymphomas, particularly diffuse large B-cell lymphoma (DLBCL). Due to its rarity, available evidence is largely derived from small case series and retrospective analyses, highlighting the need for additional reports from diverse populations. METHODS: A retrospective, observational, descriptive study was conducted at a tertiary referral center in Mexico. All cases diagnosed as PBL between 2005 and 2020 were retrieved from the institutional pathology database. Inclusion criteria consisted of a histopathological diagnosis of primary lymphoma involving the breast with availability of complete histopathological material, including paraffin blocks and immunohistochemical studies. Descriptive statistics were used. Continuous variables are expressed as mean ± standard deviation, and categorical variables as absolute frequencies and percentages. Due to the small sample size, no inferential statistical analysis was performed. RESULTS: Six cases met the diagnostic criteria for PBL (N = 6), and all patients were women. The mean age at diagnosis was 38.2 ± 19 years (range, 19-66). DLBCL was the most frequent subtype (4/6, 66.7%), followed by classical Hodgkin lymphoma (1/6, 16.7%) and B-lymphoblastic lymphoma (1/6, 16.7%). Left breast involvement was observed in three cases, right-sided disease in one, bilateral presentation in one, and one case lacked specified laterality. CONCLUSIONS: In this single-center Mexican series, patients were diagnosed at a younger age than typically reported in the international literature. DLBCL was the predominant subtype. These findings suggest the possibility of population-specific epidemiological patterns and underscore the need for larger regional studies to clarify potential differences in disease presentation.