The ret protooncogene is expressed in predominantly epithelial human thymomas

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