Histopathological and Clinical Features of HER2-Positive Breast Cancers across Hormone Receptor Subgroups: A...

HER2-positive breast carcinomas are a heterogeneous group with various clinicopathological characteristics depending on hormone receptor (HR) status. This study aimed to analyze and compare the clinical and histopathological features of HER2-positive breast carcinomas across three subgroups: Group 1: Triple-positive (ER+/PR+/HER2+), Group 2:ER-positive only (ER+/PR-/HER2+), and Group 3: HER2-enriched (ER-/PR-/HER2+).

This was a single-institution, retrospective, cross-sectional study conducted over 42 months (January 2021-June 2024) at a tertiary care center comprising of 117 HER2-positive breast carcinoma cases. The demographic, clinical, and histopathological parameters were studied retrospectively. Statistical analysis was performed via SPSS Version 29.0, employing ANOVA and chi-square tests, with p < 0.05 considered significant.

Among 117 HER2-positive breast cancer patients, left and right breast involvement was nearly equal. Most were diagnosed via core biopsy (83.8%), with the upper outer quadrant most commonly affected (42.9%). Invasive breast carcinoma of no special type was the predominant subtype. The HER2-enriched group (Group 3) had the highest mean age (57.28 years; p = 0.001) and the most Grade 3 tumors (36.1%; p = 0.005). Although Group 2 (ER-positive) had the largest mean tumor size (4.31 cm), the difference was not statistically significant ( p = 0.143). Lymphovascular invasion, necrosis, Ductal carcinoma in situ (DCIS), and skin involvement showed no significant differences across groups. ANOVA showed significant variation in age and grade, and post-hoc analysis confirmed that Group 1 vs Group 3 differed significantly in both age ( p = 0.001) and grade ( p = 0.004).

HER2-positive breast carcinomas show variability by HR status. The HER2-enriched subtype is associated with older age, higher histological grade, and advanced nodal stage, suggesting a more aggressive phenotype. Recognizing these patterns aids in accurate prognostication and guiding individualized therapy.