Discrimination of cell types in primary transitional cell carcinoma by monoclonal anti-cytokeratin antibodies

The morphologic discrimination between low and high grade malignant tumor cells arising in the urinary bladder is a major diagnostic problem in cytopathology. Using immunochemical peroxidase staining of cytokeratins (CKs) of human bladder exfoliative cytology specimens, we have been able to discriminate between transitional cell carcinoma cells, atypical cells and normal bladder cells. Commercially available monoclonal antibodies used in this study were: anti-CK 13 (Sigma K8.12), anti-CK 5, 7 and 8 (Sigma K8.13), anti-CK 19 (Sigma K4.62), and anti-CK 18 (Transformation Res. 1091). When normal bladder cells are stained with these antibodies, CK 18 is specific for superficial cells; CK 13 is specific for the basal type cells and CKs 5, 7, 8 and 19 are expressed by all urothelial cell types. Four cases diagnosed by cytopathological criteria as 'atypical' and 7 diagnosed as 'positive' (various grades) were used in this study. Cytologic diagnosis was confirmed by histopathology in 7 cases. Tissue was not available for histopathology in 4 cases. Malignant cells with a 'basal' or 'immature' phenotype preferentially stained with CK 13 and were associated with increased metastatic or malignant potential. Patients with higher grade tumors had more cells positive for CK 13 than did patients with atypical or lower grade malignancies. Patients with well-differentiated, low grade tumors predominantly shed cells that expressed CK 18 and CK 19. High grade, invasive bladder lesions were characterized by many cells expressing CK 13, and fewer cells expressing CK 19. The combination of diagnosis by morphologic criteria on Papanicolaou-stained specimens with immunochemical characterization of the same cells for CKs facilitate an accurate diagnosis of bladder lesions.