Malignant rhabdoid tumor of the colon. Report of a case with molecular analysis.

Abstract

Malignant rhabdoid tumors were first described in the kidney as a rare variant of Wilms' tumor with a "rhabdomyosarcomatoid" pattern and a particularly poor prognosis. Further studies have demonstrated these neoplasms as a distinct clinicopathologic entity. Subsequently, tumors with a similar histologic appearance, demonstrating the "rhabdoid" cells, have been found in a variety of extrarenal sites. We report here a case of malignant rhabdoid tumor of the colon studied with selected molecular techniques. This tumor demonstrated several unusual findings for malignant rhabdoid tumors of renal or extrarenal sites, including aneuploidy by flow cytometric analysis and a positive nuclear immunohistochemical staining for p53 protein, which suggests presence of p53 gene mutation. DNA analyses, however, failed to demonstrate the presence of point mutation in any of the ras family genes.