A Retrospective Study to Classify Breast Carcinomas According to Molecular Classification and to Correlate the ER, PR, HER2 Results with the Nottingham Grade and the Axillary Lymph Node Status and to Compare the Nottingham Grade with Axillary Lymph Node Status in Breast Carcinomas

Background: Breast carcinoma (BC) is a heterogeneous disease. Gene expression analyses identify several subtypes which are of prognostic and predictive importance. Aims: (1) to determine the prevalence of BC subtypes from SSWPS area patients according to molecular classification using immunohistochemistry (IHC) as surrogate markers and (2) to determine the relationship between certain pathological characteristics. Methods: We reviewed 312 cases of BC diagnosed in 2013 in our department. Molecular classification of BC was based on Estrogen Receptor (ER), Progesterone Receptor (PR), HER2/neu (HER2), HER2 CISH and Ki-67 results. Triple negative cases were subdivided into Basal-like and Unclassified groups using CK5/6, CK14 and EGFR. The ER, PR and HER2 results were correlated with Nottingham grade (NG) and axillary lymph node (ALN) status. Results: The commonest molecular subtype was Luminal A subtype (45%) followed by Luminal B (38%) [Luminal B HER2 negative (32%) and Luminal B HER2 positive (6%)], HER2 positive (7%), Basal-like (9%) and Unclassified subtype (2%). Positive ER and PR findings were inversely correlated with higher NG (p≤0.0001) whereas high NG was positively correlated with positive HER2 status (p≤0.0001). There was no correlation between ALN status and ER, PR and HER2 results. A statistically significant correlation was found between higher NG and number of ALN metastasis. Majority of Luminal A subtype BCs were either of NG 1 or 2 (135 cases, 96.4%). Amongst the NG 3 cases, majority of the BCs belonged to Luminal B HER2 negative subtype (44.14%). Conclusion: This study shows that molecular classification of BC by IHC is practical and is necessary for therapeutic decision and prognosis as molecular testing is not always feasible in routine laboratories.