Intrinsic Molecular Subtyping of Breast Cancer in Low Resource Setting

Background: Immunohistochemistry is an invaluable technique used clinically in the characterisation of breast cancer in various intrinsic subtypes. Such characterisation into the intrinsic subtypes is of great prognostic value in the management of breast cancer.

Methodology: Two hundred and seventy-six cases of formalin-fixed paraffin-embedded (FFPE) tissue blocks were selected from 2012 – 2016 cases from Korle Bu Teaching Hospital (KBTH). The hormonal markers Estrogen Receptor (ER), Progesterone Receptor (PR), HER 2 and Ki67 were determined for cases using a semi-automated immunohistochemical method with commercially prepared antibodies from BioSB.

Results: The commonest intrinsic molecular subtype is luminal type A (42.2%), luminal B (12.3%), Her 2+ (10.5) and TNBC (35.0%). There is a significant association between tumour size and all the intrinsic subtypes (P < 0.05). The luminal type A and B were associated with size <5cm while TNBC was associated with size ≥5cm. Ki67 was unfavourable for 65.5% of the cases with 21.8% favourable and 12.7% being borderline. The various subtypes are significantly associated with vascular invasion.

Discussion and Conclusion: This study has shown that a greater percentage of breast cancer among Ghanaian patients are hormonal positive and should have done well on hormonal treatment but did not because of the late presentation and tumour characteristics. The study confirmed previous results of the higher incidence of TNBC in African women as compared to other ethnic groups.