Colorectal adenocarcinoma with heterotopic bone.

Abstract

Objective: Heterotopic bone is rarely found in colorectal carcinoma with low incidence of 0,4 %. We report a case of a 75-years old male presenting with constipation, vomiting and abdominal, i.e. acute abdomen, due to large bowel obstruction. He underwent urgent surgical operation. Method: The received material was a total colectomy with egsophytic tumour in the sigmoid colon, measuring 4 cm in length, with proximal dilatation of 16 cm in diameter. Standard tissue samples were embedded in paraffin blocks and Hematoxylin-Eosin and imunohistochemical stainings were made. Results: Histological analysis showed poorly differentiated adenocarcinoma Stage IVA. We found abundant desmoplastic stroma, partly hyalinised, with deposition of osteoid and focal formation of well-defined osseous islands of various shapes and sizes, with evident osteoblasts arranged as osteoplasts, with focally formed Haversian canals. Immunohistochemical staining showed CK18(+), Vimentin(-) signal for tumour cells, and Vimentin(+) signal for the osteoid, Osteopontin(+) signal for osteoblasts and osteoid. Conclusion: Pathogenesis is unclear, but there are theories describing fibroblast metaplasia into osteoblasts or production of BMP-2 and FGF-2 by tumour cells, inducing bone formation. The finding of osseous metaplasia in colorectal carcinoma does not change the prognosis, although is very important to differentiate this entity from carcinosarcoma, that have poor prognosis.