UNDIFFERENTIATED CARCINOMA - AN IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL-STUDY

Twenty-eight undifferentiated carcinomas (UCs) were immunohistochemica lly investigated with antibodies against cytokeratins (CKs), vimentin, p53 protein, c-erbB-2 protein and CEA. The diagnoses were based on th e findings of conventional histophathology, immunohistochemistry and e lectron microscopy. CKs8, 18 and 19 were the CKs most frequently prese nt in these tumors, in 61%, 61% and 82% of the cases, respectively. Ni ne of the 28 (32%) UCs were CKs5/6 positive. Expression of CK20 was fo und in three (11%) cases. Four UCs were sub-type Cks negative, but one of them was confirmed AE1/AE3 positive. P53 protein overexpression wa s found in nine (32%) cases. One of the patients with p53 protein posi tive tumors has been alive for 174 months. Nine (32%) UCs expressed vi mentin, which included all of the three thyroid UCs. Comparing with ou r previous study of squamous cell carcinomas, we found that vimentin a nd CK18 are more frequently expressed in UCs. The overexpression of p5 3 protein is similar in the two groups of carcinomas and thus, p53 pro tein is not a differentiation marker in these tumors. Finally, we reco mmend the use of a CK ''cocktail of antibodies'' in the diagnosis of U Cs.