Profile of molecular subtyping of breast cancer and clinico-pathological features in Mankweng Hospital breast oncology clinic, Limpopo Province, South Africa

Background. Breast cancer is recognised as a heterogeneous disorder, comprising a number of subcategories of several cellular compositions, molecular alterations as well as clinical behaviour. Across the world, research has been able to show that the most common molecular subtype is luminal A, followed by triple negative and human epidermal receptor 2 (HER2)-positive (non-luminal) subtype. However, another study found that the most common molecular subtype was HER2/neu amplification, suggesting that subtypes case frequencies differ in different people. Objectives. To determine the case frequency of molecular subtypes of breast cancers and the associated clinicopathological features in women from Limpopo Province, South Africa. Method. We performed a retrospective, cross-sectional descriptive study from July 2021 - June 2021 at Mankweng Hospital breast oncology clinic. The inclusion criterion was all women with histologically confirmed breast cancer. Result. We identified 222 women who met the inclusion criteria, and the age range (median) was 25 - 91 (54.8) years. The majority of the women came from the Vhembe district (28%; n=62), followed by Capricorn district (26%; n=59), Mopani district (17%; n=38), Sekhukhune district (16%; n=35), and Waterberg district (13%; n=28). Histology revealed that the most common type was invasive ductal carcinoma (no special type; 91.44%; n=203), followed by invasive mucinous carcinoma (4%; n=9). The most predominant molecular subtype was luminal B (48.19%; n=107), followed by luminal A (22.97%; n=51), triple negative (17.12%; n=38) and 11.75% (n=26) overexpressed HER2. More than one-third of the cancers were HER2-positive (40.54%; n=90), and 59.46% (n=132) were HER2-negative. The majority of patients presented with late-stage cancer (62.16%; n=138), and the rest presented with early-stage (I and II) disease (37.84%; n=84). Conclusion. The majority of our patients had luminal subtypes and hormonal receptor-positive breast cancers, which should be associated with very good clinical outcomes. However, the majority of patients presented late with advanced-stage disease and high Ki-67 expression. Therefore, research is required to help us understand why in our context patients present late with advanced-stage disease.