IMMUNOHISTOCHEMICAL STUDY OF C-ERBB-2 EXPRESSION IN CARCINOMA EX-PLEOMORPHIC ADENOMA

A series of 19 cases of carcinoma ex-pleomorphic adenoma was studied f or the immune-expression of c-erbB-2 oncoprotein. Twelve rumours showe d a malignant component with only one histological type; in the remain ing seven there was co-existence of areas of various carcinoma types, adenocarcinoma NOS being the most frequent, Membranous c-erbB-2 reacti vity was found in 21.1% of the cases, all corresponding to high-grade adenocarcinomatous areas, The low-grade carcinoma types that formed th e malignant mixed tumours components were negative, Benign pleomorphic adenoma areas, either adjacent or intermingled with carcinomatous are as, were also consistently negative, proving that c-erbB-2 accumulatio n is associated with the acquisition of the malignant phenotype. The f inding of a preferential association between c-erbB-a overexpression a nd high-grade malignant mixed tumour may indicate prognostic implicati ons for the oncogene protein and may also be indicative of its specifi c relationship with the putative pathway of malignant transformation i n pleomorphic adenomas.