Molecular Subtypes and Prognostic Biomarkers of Breast Carcinoma in Different Age Groups: Findings from a Tertiary Care Hospital in Saudi Arabia

Background: Breast cancer is a leading cause of cancer-related deaths globally, with a rising incidence in Saudi Arabia. However, limited studies from Saudi Arabia have reported the molecular subtypes and prognostic biomarkers of breast cancer. Objectives: This study aimed at comparing the clinicopathological and immunohistochemical characteristics of breast cancer among two age groups from Saudi Arabia. Methods: A retrospective study was conducted on Saudi female patients diagnosed with breast cancer between 2017 and 2022 at a tertiary care hospital in Riyadh. Patients were stratified into two age groups: aged ≤40 years and >40 years. Tumor size, grade, stage, and molecular subtypes were compared among these age groups. Results: The study comprised 300 females with breast cancer (mean age: 53.2 ± 12.6 years). Majority of patients (54.3%) were postmenopausal. The most common tumor type overall was invasive breast carcinoma of no special type (84%). In patients aged ≤40 years, most patients had T4 tumor size (39%) and were at an advanced stage (69.2%). Compared with those aged >40 years, patients aged ≤40 years had significantly higher Ki-67 index ( P < 0.001), lymph node spread ( P = 0.009) and poor short-term survival ( P < 0.024). Luminal A tumors were more common in the older age group, while significantly higher proportion of young patients had triple negative breast cancer (TNBC) ( P = 0.035). Cox regression analysis demonstrated advanced stage (hazard ratio [HR]: 12.4; P = 0.002) and TNBC (HR: 11.9; P = 0.002) as factors that raised the risk of mortality compared to early stage and luminal A type, respectively. Conclusion: Breast cancer patients aged ≤40 years exhibited more aggressive clinicopathological features, including higher grade, advanced stage, triple negative receptor status, and poorer short-term survival compared with patients aged >40 years.