Cytokeratins, the intermediate filaments, are expressed by many epithelial cells. Immunohistochemistry revealed the presence of
cytokeratin-19 both in bronchial epithelium and in
lung cancer cells. The aim of our study was to establish the value of serum
cytokeratin-19 estimation by immunoenzymatic assay (Enzymun
Cyfra 21-1, Boehringer Mannheim) in the patients (pts) with
lung cancer (Ic). 153 pts (104 men, 49 women, median age 50 years) entered this study. The group consisted of 37 pts with benign
lung diseases (control group), 56 pts with squamous cell Ic, 37 pts with small cell Ic and 23 with
adenocarcinoma. Cut off value was determined at 4 ng/ml, with 96% of specificity. Elevated
cytokeratin-19 values were found in 41% of pts with
lung cancer (45% of squamous cell Ic, 39% of
adenocarcinoma and 35% of small cell Ic). Median
cytokeratin-19 values were 2.2 ng/ml in the control group, 3.4 ng/ml in squamous cell Ic, 3.3 ng/ml
adenocarcinoma and 2.9 in small cell Ic.
Cytokeratin-19 elevation was observed more often in non small cell Ic pts with advanced disease, stage III--46%, stage IV--50% than in early stages (I + II)--34%. In small cell Ic pts the frequency of
cytokeratin-19 elevation was 20% in limited disease versus 45% in extensive disease. We conclude that
cytokeratin estimation is not valuable in the recognition of histologic type of
lung cancer, although elevated levels are seen more often in squamous cell Ic.
Cytokeratin-19 estimation may be also helpful in
lung cancer staging.