OSSIFYING FIBROMYXOID TUMOR OF THE RETROPERITONEUM

A case of ossifying fibromyxoid tumor (OFMT) in an unusual site, the r etroperitoneum, in a 71 year old Japanese man is reported. The well de marcated tumor contained a large amount of mature bony tissue within t he tumor. The tumor cells were round to spindle-shaped, and showed a h igh cellularity in some areas and were loosely arranged in other areas . Although the majority of tumor cells expressed vimentin, neuron spec ific enolase and Leu-7, there were no tumor cells positive for S-100 p rotein, myogenic or epithelial markers. We would like to emphasize tha t tumors classified as OFMT contain a wide spectrum of histologic feat ures and heterogeneity.