Association between molecular subtypes of breast cancer and surgical margin status analysis from Assam, India

Breast cancer (BC) is common in young women in India, with 68.8% of cases occurring under 50 years. Key factors regularly evaluated to predict the prognosis and treatment response include tumor size, lymph node, ER, PR, HER2 status, tumor grade, and age. The molecular subtypes Luminal A, Luminal B, HER2- over expressed and triple negative breast cancers carry different treatment plan and prognosis. Regardless of surgical strategy, margin status of the resection specimen remains one of the most important factors of recurrence.

This study investigated the association between molecular subtypes and surgical margin status, as well as other prognostic parameters, in women from North Eastern India, where triple negative breast cancer (TNBC) subtype and poor 5-year survival rates are prevalent.

This cross-sectional study was conducted at a tertiary care centre in Upper Assam, North East India, from October 2019 to March 2025. BC cases that underwent breast conservative surgery (lumpectomy) or modified radical mastectomy (MRM) and fulfilled the inclusion criteria were included. Tumors were classified into molecular subtypes by immunohistochemistry. Surgical margin status was assessed by histopathological examination, with margins considered positive if neoplastic cells were present at the inked margin. Prognostic parameters with surgical margin status were analyzed using Pearson's Chi-square test and Fisher's exact test.

A total of 155 breast cancer cases were included in the study with average age of 47 years. The distribution of molecular subtypes was: TNBC (36.77%), Luminal A (29.67%), Luminal B (18.06%), and HER2-enriched (15%). Histologic grade III tumors were predominant (58.70%). Total positive margin was 34.83% cases. Positive surgical margins were associated with HER2-enriched subtype (p < 0.05) and grade I tumors. Lymph node involvement was 77%, with stage 2 and 3 accounting for 80.64% of cases.

Our study highlights the high prevalence of TNBC and the significant association between positive tumor margins and HER2-enriched subtype. The findings emphasize the need for tailored treatment strategies to improve outcomes in this population.