CYTOKERATIN EXPRESSION IN PRENEOPLASTIC LESIONS AND EARLY SQUAMOUS-CELL CARCINOMA OF THE BRONCHI

Cytokeratins are expressed in varying combination in the course of dif ferentiation of epithelial cells and tumor cells. This is the first re port of systematic immunohistochemical (ABC-method) investigations con cerning the expression of different cytokeratin types (KL 1, CK 4, 10 and 17) within the transformation of the bronchial mucosal epithelium with epithelial hyperplasia to potential preneoplasia and early squamo us cell carcinoma of the lung. In bioptical obtained specimens from 35 patients, 63 areas with diagnosis of regular bronchial mucosa (n = 10 ), basal cell hyperplasia (n = 9), goblet cell hyperplasia (n = 10), s quamous cell metaplasia (n = 11), dysplasia I-III (n = 13), carcinoma in situ in the border zone of squamous cell carcinoma (n = 10) and in 5 surgically obtained specimens with findings of an early squamous cel l carcinoma of the bronchus (n = 5), the expression of different cytok eratin types was investigated. The specimens were fixed in formalin an d embedded in paraffin for lightmicroscopical and immunohistochemical investigations (ABC-method)(6). KL 1 was detected in all regular and p athological mucosal epithelia, CK 4 in basal cells, squamous cell meta plasia, potentially preneoplastic changes and early squamous cell carc inoma of the bronchus. CK 10 was expressed only in early squamous cell carcinoma of the bronchus, and CK 17 in varying quantity in hyperplas tic, preneoplastic and cancerous lesions of the bronchial mucosa. Our results reveal an increasing expression of squamous epithelial type-cy tokeratins (CK 4, CK 17) in hyperplastic and metaplastic lesions of th e bronchial mucosa. In dysplastic lesions and carcinomata In situ, a q uantitative, as well as qualitative decrease of the CK 4- and CK 17-ex pression with a heterogeneous expression pattern for CK 17 was found. The heterogeneous neo-expression of CK 10 in early squamous cell carci noma of the bronchus has to be emphasized.