Molecular Subtypes and Treatment Modalities in Breast Cancer in a Brazilian Military Hospital: An Observational Study

Breast cancer is a global public health concern and the most common malignancy in women, with a lifetime risk of 12.5%. It is also the most frequently diagnosed cancer, accounting for 11.6% of all cases. This study is aimed at describing the clinical, anatomopathological, and sociodemographic profile of women diagnosed with breast cancer at a public military hospital in Brazil, and evaluating the association between molecular subtypes and the type of treatment received. This was an observational, cross‐sectional, and quantitative study. Data were extracted from the hospital′s electronic medical records (AGHUse platform) in 2022 and 2025, involving a total of 102 women. Most cases were diagnosed at clinical Stage II (49.0%). Regarding molecular classification, the most prevalent subtype was Luminal B (47.1%), followed by Luminal A (18.6%), HER2‐enriched luminal (16.7%), triple negative (12.8%), and HER2‐enriched nonluminal (4.9%). A total of 54.9% of the tumors had histological Grade 2. Most patients (71.6%) did not present metastases, whereas a minority did (28.4%). Treatment decisions were guided by molecular subtypes, with triple negative and HER2‐enriched subtypes more frequently receiving neoadjuvant or palliative treatment and luminal subtypes predominantly treated with adjuvant therapy; no statistically significant association was found between individual molecular subtypes and the overall type of treatment received, which is likely attributable to the limited statistical power resulting from the small sample size within the neoadjuvant subgroup ( n = 36). The total cohort for neoadjuvant analysis consisted of 36 patients, with a global pathological complete response (pCR) rate of 47.2% ( n = 17). Within the residual disease group ( n = 19), qualitative stratification revealed that 73.7% ( n = 14) achieved a partial response (pPR), whereas 26.3% ( n = 5) presented a minimal response. Although the global association between molecular subtypes and pathological response (pCR vs. RD) did not reach statistical significance ( p = 0.2831), a subgroup analysis comparing aggressive phenotypes (triple negative and HER2‐enriched) against luminal phenotypes (Luminal A and B) was evaluated ( p = 0.169; OR = 3.61; 95% CI: 0.86–15.20). Aggressive subtypes demonstrated a clinically higher rate of pCR (59.1% vs. 28.6%), supporting biological aggressiveness as a driver of chemosensitivity in this cohort. These results contribute to clinical decision‐making and a better understanding of the disease profile in women treated in military hospitals. Moreover, it highlights the need for better response prediction markers for pathological response.