CHANGES OF CYTOKERATIN AND INVOLUCRIN EXPRESSION IN SQUAMOUS-CELL CARCINOMAS OF THE SKIN DURING PROGRESSION TO MALIGNANCY

The detection of cytokeratins in neoplastic tissues by immunohistochem ical methods has numerous diagnostic and investigative applications, b ecause cytokeratins are usually conserved in tumour cells during malig nant transformation. Recently, however, it has been reported that prog ression to malignancy is associated with commencement of expression of low-molecular-weight cytokeratins. In the present study, 42 specimens from 35 cases of squamous cell carcinoma (SCC) of the skin were analy sed by immunohistochemical techniques, using polyclonal anti-involucri n antibody and a panel of monoclonal antikeratin antibodies, in order to investigate the nature and differentiation of SCCs. The expression of cytokeratins and involucrin in well-differentiated SCCs was similar to that in normal epidermis. In contrast with well-differentiated SCC s, the expression of differentiation-specific cytokeratins and involuc rin was diminished in the immature tumour cells in proportion to the m alignancy of the SCCs. Some antibodies, however, stained all tumour ce lls, irrespective of the degree of malignancy. Furthermore, expression of simple epithelial and non-cornifying stratified squamous epithelia l cytokeratins was observed in atypical tumour cells of poorly differe ntiated SCCs. It is of interest that similar expression was noted in m any tumour cells in the lymph node metastases and in some tumour cells in the primary cutaneous lesions. Cytokeratin expression similar to t hat in normal epidermal keratinocytes was conserved in well-differenti ated SCCs, but the expression of cytokeratins changed during progressi on to malignant transformation. The expression of simple epithelial or non-cornifying stratified squamous epithelial cytokeratins in cutaneo us SCCs may be a marker for their capability of invasion and metastati c potential.