Background: A unique finding of an extraskletal osseous lesion of the omentum was detected in a 53-yearold woman who had diffuse infiltrative gastric adenocarcinoma associated with serosal
metastases.Case Report: The patient was a 53-year-old woman and she had epigastric pain, regurgitation and dispeptic complains for 12 years. At esophago-gastroduodenoscopy,there was a mass in the antrum in 10 cm diameter. Ultrasound and CT examination showed diffuse thickening of the gastric wall and a mass situated in the antral region.The biopsy was performed, and the result revealed poorly differentiated adenocarcinoma. Then, the patient underwent surgical resection. During the initial intraoperative evaluation of the abdomen, there was only a calcificnodule in the omentum majus in 0.5 cm diameter. Thus, total gastrectomy, omentectomy, ophagojejunostomy were performed.Resected tumor seen in the antral region was measured in a size of 10x6x1cm. Calcific nodule was measured as 0.5 cm in the omentum majus. The pathological diagnoses were diffuse infiltrative gastric adenocarcinoma and heterotopic bone formation in omentum tissue.Conclusions: Heterotopic bone formation in the omentum is exceedingly rare event. Therefore, we presented an osseous metaplasia case in the omentum with diffuse infiltrative adenocarcinoma of stomach and we tried to discuss the probable pathogenetic mechanisms for ossification in the omentum.

Keywords: Heterotopic bone formation, Omentum tissue, Diffuse infiltrative gastric adenocarcinoma