A Retrospective Hospital-Based Study of HMGCR Expression in HER2 IHC 2+ and 3+ Breast Cancer

Objective: The role of HMG-CoA reductase (HMGCR) in relation to prognostic and treatment predictive information of HER2 positive breast cancer has been newly explored. In this study, we aimed to determine the expression of HMGCR in HER2 immunohistochemistry (IHC) scores of 2+ and 3+ breast cancer and to correlate with the patients’ outcomes.Methodology: Using a cross-sectional design, invasive breast carcinoma of no special type (NST) and HER2 IHC scores of 2+ and 3+ cases were selected over a 50-month period in Hospital Sultanah Bahiyah (HSB), Alor Setar. IHC staining for HMGCR was performed on paraffin-embedded tissues at the Pathology Laboratory, Hospital Universiti Sains Malaysia (HUSM), Kubang Kerian using the standard staining procedure. The results were correlated with the patient’s demographic and clinicopathological data. Results: A total of 59 cases of HER2 IHC 2+ and 3+ invasive breast carcinoma were identified. The cases were predominant in young Malay women with tumours smaller than 50mm, higher grade and positive for lymphovascular invasion, axillary lymph nodes involvement and ER/PR expressions. HMGCR was positively expressed in HER2 IHC 2+ and 3+ breast cancer cases, which the staining intensities varied from weak, moderate to strong. Majority of the cases were scored 1+ for HMGCR expression. A low-positive HMGCR was more likely to be associated with less favourable outcomes of patients with HER2 IHC 2+ and 3+. However, the associations were statistically not significant. Conclusion: A study in a larger cohort of tumour samples is needed to further validate HMGCR expression as a potential prognostic biomarker for HER2 positive breast cancer. It is also suggested that all the HER2 IHC 2+ and 3+ cases need to be gene amplified using FISH analysis.