Immunohistochemistry of cytokeratin proteins in squamous and transitional cell lesions of the urinary tract.

Expression of low and high molecular weight cytokeratin proteins was investigated immunohistochemically in a variety of transitional and squamous epithelial lesions of the urinary tract with and without schistosomiasis. The monoclonal antibodies used were CAM 5.2 and NCL5D3 for low, PK 63 and 121 for high, and MAK 6 for a broad range of intermediate molecular weight cytokeratins. On staining with CAM 5.2 and NCL5D3, urothelial hyperplasias (n = 12) and grades 1 (n = 5) and 2 (n = 10) papillary transitional cell carcinomas showed labelling patterns quite distinct from carcinoma in situ (n = 4) and non-papillary grades 2 (n = 6) and 3 tumours (n = 3). Among squamous lesions only focal positivity was obtained in 14 of 22 moderate to poorly differentiated squamous cell carcinomas. By contrast, PK 63 and 121 stained squamous lesions exclusively. MAK 6 stained the whole range of urothelial and squamous lesions with the exception of squamous metaplasias. Polyclonal antikeratin adequately labelled spindle cell areas of high grade tumours. The distinctive staining patterns given by these or similar antibodies may help in the identification of squamous metaplasia and in diagnosing tumours of the urothelium.