Cyclooxygenase-2 expression in lung cancer cells evaluated by immunocytochemistry

Cyclooxygenase-2 (COX-2) expression may be a prognostic factor in lung cancer. In previous studies, COX-2 expression has almost exclusively been evaluated with immunohistochemical methods performed on histology sections of tissue biopsies. However, in clinical practice, lung cancer is often diagnosed with cytological techniques only. We present methodology and results from analysis of COX-2 expression with immunochemistry on cytological material in 53 patients with lung cancer. Preparation and staining with the method established at our laboratory were easy to perform and resulted in good quality slides. The percentage COX-2-stained cells and the intensity of staining varied widely between and within the different cases. The proportion of positively stained tumor cells was as follows: <1% in 20 patients, 1-10% in 7 patients, 11-50% in 17 patients, and more than 50% in 9 patients. In 17 cases, groups of cells with different intensity of COX-2 staining were found in the same slide. In conclusion, immunocytochemical analysis of COX-2 expression is technically easy to perform with routine diagnostic procedures. There is a great variation in the proportion of COX-2-positive cells among patients and in the intensity of staining among individual cells in many single cases.