Cytokeratin expression in preneoplastic lesions and early squamous cell carcinoma of the bronchi.

Cytokeratins are expressed in varying combination in the course of differentiation of epithelial cells and tumor cells. This is the first report of systematic immunohistochemical (ABC-method) investigations concerning 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 squamous 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), squamous 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 cell carcinoma of the bronchus (n = 5), the expression of different cytokeratin types was investigated. The specimens were fixed in formalin and embedded in paraffin for lightmicroscopical and immunohistochemical investigations (ABC-method). KL 1 was detected in all regular and pathological mucosal epithelia, CK 4 in basal cells, squamous cell metaplasia, potentially preneoplastic changes and early squamous cell carcinoma of the bronchus. CK 10 was expressed only in early squamous cell carcinoma of the bronchus, and CK 17 in varying quantity in hyperplastic, preneoplastic and cancerous lesions of the bronchial mucosa. Our results reveal an increasing expression of squamous epithelial type-cytokeratins (CK 4, CK 17) in hyperplastic and metaplastic lesions of the bronchial mucosa. In dysplastic lesions and carcinomata in situ, a quantitative, as well as qualitative decrease of the CK 4- and CK 17-expression with a heterogeneous expression pattern for CK 17 was found. The heterogeneous neo-expression of CK 10 in early squamous cell carcinoma of the bronchus has to be emphasized.