Clinicopathological Characteristics of Young-Onset Breast Cancer Patients Stratified by Molecular Subtypes at H. Adam Malik Hospital

Aim To examine and evaluate the clinicopathological characteristics of young-onset breast cancer across molecular subtypes in patients from Southeast Asia, with a specific focus on those treated at H. Adam Malik Hospital, Indonesia. Methods A descriptive observational study with a cross-sectional design was conducted on medical records of breast cancer patients aged <40 years treated at H. Adam Malik Hospital from January 2017 to December 2022. Data included demographic, clinical, histopathological, and immunohistochemical findings. Statistical analyses were performed descriptively. Results Among the 104 patients analyzed, 71 (69.2%) had T4 tumors, and 49 (47.1%) had NST-type tumors. Most cases lacked ER (72, 69.2%) and PR (71, 68.3%) expression. A total of 41 patients had poorly differentiated tumors, with the majority at stage IV. The HER-2 positive subtype was most common (39, 37.5%), followed by Luminal B (31, 29.8%) and TNBC (22, 21.2%). Conclusion Young-onset breast cancer at H. Adam Malik Hospital predominantly features advanced stages, aggressive histopathological grades, and a high prevalence of HER2-positive and Luminal B subtypes. These findings highlight the importance of early detection and personalized treatment approaches.