Metaplastic bone formation in the abdominal wall--an incidental finding in a patient with gastric cancer. Case report and hypothesis about its histogenesis.

A 64-year-old man was hospitalized showing symptoms suggesting gastric cancer. The gastroscopy showed a 70 × 30-mm tumor. The intraoperatory findings indicated an inoperable gastric tumor located in the antrum and gastric body, which invaded the spleen and pancreas. The abdominal incision was closed without performing gastrectomy. Considering his general condition, after 1 month, he was transferred to our hospital. We decided to perform a total gastrectomy of necessity, spleno-pancreatectomy, and dissection of regional lymph nodes. The surgical incision was performed along to the previous one. At palpation, a well-defined nodule with hard consistency was observed in the surgical scar, which microscopically was composed by osteoblasts-lining mature lamellar bone intermingled with osteoid and cartilage in the intermediary layer and fibroblasts in the central area, without atypia. The final diagnosis was localized metaplastic bone formation. This is a rare condition which can be related to trauma or surgery and should be differentiated by foreign-body granuloma and osteosarcoma.