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.