Molecular Subtypes of Indonesian Breast Carcinomas - Lack of Association with Patient Age and Tumor Size.

Objective: Breast carcinoma (BC) is a heterogeneous disease that exhibits variation in biological behaviour, prognosis and response to therapy. Molecular classification is generally into Luminal A, Luminal B, HER2+ and triple negative/basal-like, depending on receptor characteristics. Clinical factors that determined the BC prognosis are age and tumor size. Since information on molecular subtypes of Indonesian BCs is limited, the present study was conducted, with attention to subtypes in relation to age and tumor size. Methods: A retrospective cross-sectional study of 247 paraffin-embedded samples of invasive BC from Dr. Sardjito General Hospital Yogyakarta in the year 2012- 2015 was performed. Immunohistochemical staining using anti- ER, PR, HER2, Ki-67 and CK 5/6 antibodies was applied to classify molecular subtypes. Associations with age and tumor size were analyzed using the Chi Square Test. Results: The Luminal A was the most common subtype of Indonesian BC (41.3%), followed by triple negative (25.5%), HER2 (19.4%) and luminal B (13.8%). Among the triple negative lesions, the basal-like subtype was more frequent than the non basal-like (58.8 % vs 41.2%). Luminal B accounted for the highest percentage of younger age cases (< 40 years old) while HER2+ was most common in older age (> 50 years old) patients. Triple negative/basal-like were commonly large in size. Age (p = 0.080) and tumor size (p = 0.462) were not significantly associated with molecular subtypes of BC. Conclusion: The most common molecular subtype of Indonesian BC is luminal A, followed by triple-negative, HER2+ and luminal B. The majority of triple-negative lesions are basal-like. There are no association between age and tumor size with molecular subtypes of Indonesian BCs.