Background: Breast cancer is a heterogeneous disease with molecular subtypes that have biological distinctness and different behavior. They are classified into luminal A, luminal B, Her-2 and triple negative/basal-like molecular subtypes. Most of breast cancers reported in Indonesia are already large size, with high grade or late stage but the clinicopathological features of different molecular subtypes are still unclear. They need to be better clarified to determine proper treatment and prognosis. Aim: To elaborate the clinicopathological features of molecular subtypes of breast cancers in Indonesian women. Materials and
Methods: A retrospective cross-sectional study of 84 paraffin-embedded tissues of breast cancer samples from Dr. Sardjito General Hospital in Central Java,Indonesia was performed. Expression of ER, PR, Her-2 and Ki-67 was analyzed to classify molecular subtypes of breast cancer by immunohistochemistry. The relation of clinicopathological features of breast cancers with molecular subtypes of luminal A, luminal B, Her-2 and triple negative/basal-like were analyzed usingPearson`s Chi-Square test. A p-value of <0.05 was considered statistically significant.
Results: Case frequency of luminal A, Luminal B, Her-2+ and triple negative/basal-like subtypes were 38.1%, 16.7%, 20.2% and 25%, respectively. Significant difference was found in breast cancer molecular subtypes in regard to age, histological grade, lymph node status and staging. However it showed insignificant result in regard to tumor size. Luminal A subtype of breast cancer was commonly found in >50 years old women (p:0.028), low grade cancer (p:0.09), negative lymph node metastasis (p:0.034) and stage III (p:0.017). Eventhough the difference was insignificant, luminal A subtype breast cancer was mostly found in small size breast cancer (p:0.129). Her-2+ subtype breastcancer was more commonly diagnosed with large size, positive lymph node metastasis and poor grade. Triple negative/basal-like cancer was mostly diagnosed among <50 years old women.
Conclusions: This study suggeststhat immunohistochemistry-based subtyping is essential to classify breast carcinoma into subtypes that vary in clinicopathological features, implying different therapeutic options and prognosis for each subtype.