THE RET PROTOONCOGENE IS EXPRESSED IN PREDOMINANTLY EPITHELIAL HUMAN THYMOMAS

Thymomas are thymic tumors composed of epithelial cells with various n umber of lymphocytes. On the basis of lymphocytes number, they can be histologically classified into predominantly lymphocytic, predominantl y epithelial and mixed lympho-epithelial. These tumors are rare and th eir prognosis is not well known yet. In this study we demonstrate by i n situ hybridization the presence of RET transcripts in the medullary part of normal murine thymus and in epithelial thymomas. Conversely RE T expression was not detected in the cortical part of the thymus and i n thymomas with the predominance of the lymphocytic component, suggest ing that its expression could be a specific marker of the predominantl y epithelial histotype.