Objectives: This study aims to evaluate and compare four breast cancer subtypes defined by immunohistochemistry expression of ER, PR, and HER-2 in correlation with Ki-67 and GATA-3 expression.
Methods: Slides from 89 paraffin blocks of invasive breast cancer patients with four molecular subtypes based on HER-2, ER, and PR expression were then stained with Ki-67 and GATA-3 antibodies to evaluate their expression in correlation with molecular subtype and metastases to lymph nodes.
Results: This study was a retrospective study of 89 invasive breast cancers. Luminal A; Luminal B; HER2+; and triple-negative types were 35 (39.3%), 10 (11.2%), 27 (30.3%), and 17 (19.1%) samples. Expression of Ki-67 was increased in triple-negative (TN) tumor compared to non-triple-negative (non-TN) tumor subtypes (p < 0.05). This Ki-67 expression was inversely correlated with the positivity of hormone receptor expression related to lymph-node metastases in TN-type tumors. Sixty-two (57%) samples were immunohistochemically positive for GATA-3. GATA-3 positive samples were significantly more likely to be ER and PR-positive, Ki-67 negative, and luminal A tumors.
Conclusions: Subtype triple-negative breast cancer correlates with high expression of Ki-67 that contributes to poor prognosis of this subtype. The higher Ki-67 expression was correlated with the absence of hormone receptor expression compared with the negativity of Her-2 expression, downplay a role in nodal metastases in a triple-negative tumor. GATA-3 positive breast cancer showed luminal differentiation characterized by high ER expression and mainly was classified as luminal A type tumor with a better prognosis.
Keywords: ER; GATA-3; HER-2; KI-67; PR; breast cancer.