Osseous metaplasia is a rare phenomenon in the gastrointestinal tract. It has been reported in association with benign and malignant tumors. Here we report two cases of metaplastic ossification occuring in colonic adenocarcinomas. In both cases well formed bony spicules were present adjacent to epithelial cells. There was also intense fibroblastic proliferation in the stroma surrounding the bony spicules. In the first case osseous metaplasia was present in association with mucinous leakage. In the second case there was tumor necrosis close to bony spicules. The pathogenesis of osseous metaplasia in colorectal tumors remains unclear.

Key words: Osseous metaplasia, adenocarcinoma, colon.

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