Sub-Classification of Triple-Negative Breast Cancer using Androgen Receptor and Cytokeratin 5/6

Background: Triple negative breast cancer (TNBC) is a unique heterogenous subtypes of breast cancer which is characterized by negative estrogen, progesterone, and human epidermal growth factor receptor (HER-2) status. TNBC displays different molecular phenotype with which basal-like tumour can be identified using high molecular weight basal cytokeratin 5/6 (CK5/6).
Methods: Ninety-five (95) formalin fixed cases from Korle Bu Teaching Hospital in Ghana’s (KBTH) archives were sampled in a retrospective study from 2012-2016. Blocks of these triple-negative breast cancer was subclassified using CK5/6 and Androgen Receptor (AR) antibodies. Subclasses were also identified.
Results and Conclusion: In all ninety-five (95) TNBC cases, hormonal subtyping was sub-classified using CK 5/6 and AR. The mean ±SD of these cases was recorded as 53.96 (±13.56) years and the age range of these cases was 22-104 years. The average size (±SD) of the tumour was recorded to be 14.43(±7.62) and it had a range of 2.4-45cm. lymph nodes retrieved also had a mean ± SD of 10.35(±6.05) with an average tumour lymph nodes involvement of 2.6(± 3.697).
Invasive Ductal carcinoma was identified as the commonest histologic type of TNBC with approximately 95% of the cases. This was followed by invasive lobular (2.1%), medullary carcinoma (2.1%) and metaplastic carcinoma (1.1%).
Approximately 30% of TNBC stained positive for CK5/6.
It can however be concluded that, most TNBC are not basal-like when the basal marker CK5/6 is used.