EXPRESSION OF CK5 BASAL CYTOKERATIN DURING METASTATIC DEVELOPMENT OF BREAST CARCINOMA

Abstract

Objective. Breast cancer is a one of the most common cancers in females worldwide. Basal cytokeratin CK5 represent the marker of progenitors for glandular and myoepithelial lineages of mammary epithelium. During epithelial differentiation there is a gradual decrease of CK5 expression. The purpose of this study was to compare the expression of basal cytokeratin CK5 vs hormone receptors, HER2, Ki67 and molecular subtypes immunohistochemically defined in the primary breast carcinoma of NST type and axillar lymph node metastasis. Material and Methods. We processed immunohistochemically 91 invasive breast carcinomas of NST type and their ipsilateral axillar lymph node metastasis (LNM). Results. The majority of primary tumors were evaluated as CK5 negative (78 cases/85.7%). The majority of cases were evaluated as Luminal B (50 cases/54.9%) and Luminal A (28 cases/30.8%) tumors. The HER2 subtype was confirmed in 8 cases/8.8%, 5NP in 3 cases/3.3% and Basal-like in 2 cases/2.2%. The parallel comparison of CK5 expression at both sites, primary and metastatic, revealed that this marker is not stable during metastatic progression. The molecular subtypes were not stable during metastatic process in 21 cases/23.1%. Conclusions. The majority of NST invasive ductal breast carcinomas are CK5 negative. The molecular subtypes and CK5 are not stable during metastatic process. Cancerous cells prefer to lose this marker in the lymph node environment. The presence of cases with simultaneous expression of CK5 and hormone receptors is an open field to debate the existence of other, transient molecular subtypes. We expect a further confirmation in larger study groups