Osseous metaplasia in benign colorectal polyps.

We report two unique cases of metaplastic ossification occurring within a tubulovillous adenoma and a juvenile polyp. In both lesions, well-formed bony spicules were present that were adjacent to living epithelial cells. The metaplastic bone revealed vimentin positivity and cytokeratin negativity. The pathogenesis of osseous metaplasia in colorectal tumors remains unclear, but the process seems to have no clinical significance.