Cecal adenocarcinoma with prominent rhabdoid feature: report of a case with immunohistochemical, ultrastructural, and molecular analyses.

Colorectal adenocarcinoma with rhabdoid phenotype is extremely rare, and only 1 case of adenocarcinoma showing rhabdoid dedifferentiation has been reported. The authors present another case of cecal adenocarcinoma with prominent rhabdoid feature in a 66-year-old man. The 13-cm sized tumor consisted mainly of rhabdoid cells and partly of adenocarcinoma, and transition from adenocarcinoma to rhabdoid areas was noted. Ultrastructural analysis revealed intracytoplasmic aggregates of intermediate filaments in the rhabdoid cells. Adenocarcinoma cells were diffusely immunoreactive to cytokeratin 7 and AE1/3, but occasionally positive for vimentin. The rhabdoid cells were negative for cytokeratin 7, weakly/focally immunoreactive to AE1/3, and diffusely positive for vimentin. These results suggested that the rhabdoid cells were dedifferentiated adenocarcinoma. Analysis of the rhabdoid cells with molecular techniques is also presented.