Comparison of cytokeratin 19 expression in tumor tissue and serum CYFRA 21-1 levels in non‑small cell lung cancer

Introduction. Cytokeratin (CK) 19 belongs to type I cytokeratins. CYFRA 21-1 is an assay which detects the soluble fragment of cytokeratin 19. Objectives. The aim of this study was to compare the CYFRA 21-1 serum level with cytokeratin 19 expression in tumor tissue. Patients and methods. The CK 19 expression and CYFRA 21-1 levels were examined in 36 patients with non‑small cell lung cancer (19 men and 17 women). The mean age of the patients was 59.2 ±7.4 years. CK 19 expression was determined by immunohistochemistry using the Monoclonal Mouse Anti‑Human Cytokeratin 19 Clone BA 17 DAKO M 0772. Serum levels of CYFRA 21-1 were measured using an electrochemiluminescent immunoassay in the analyzer Elecsys 2010 (Roche Diagnostic). Results Positive cytoplasmatic staining of CK 19 was observed in all examined tumor tissues. Weak staining + (CK 1) was found in 12 (33%) patients, medium staining ++ (CK 2) in 16 (44%) patients and strong staining +++ (CK 3) in 8 (22%) subjects. The median CYFRA 21-1 serum level was 3.19 ng/ml. In 18 patients (50%) CYFRA 21-1 levels were increased (>3.3 ng/ml). In the group with increased CYFRA 21-1 serum levels the number of patients with strong CK 19 expression (CK 3) was significantly smaller (1/18 vs. 7/18; χ2 Yatesa 4.02; p = 0.045). Serum CYFRA 21-1 levels were significantly lower in patients with strong expression of CK 19 (CK 3) (Mann‑Whitney test, p = 0.04). Conclusions. A tendency towards lower serum CYFRA 21-1 levels is observed in non‑small cell lung cancer patients with strong cytokeratin 19 expression (+++) in tumor cells.