Gastric carcinoma with lymphoid stroma derived from hamartomatous inverted polyp with osteoclast-like giant cells: a case report.

Gastric carcinomas with lymphoid stroma (GCLS) are characterized by prominent stromal infiltration of lymphocyte and account for 1-4% of gastric cancers. Although, osteoclast-like giant cells (OGC) have been reported in some GCLS, OGCs in gastric tumors is exceedingly rare. A 60-year-old woman presented to our hospital after the finding of a positive fecal blood test during a routine medical check. Esophagogastroduodenoscopy revealed a Type 0-III + IIc tumor in the middle part of the gastric body. Biopsy revealed a poorly differentiated tumor and she was referred to our department. Early phase computed tomography showed thickening of the wall in the middle of the gastric body and enlargement of nearby lymph nodes. Laparoscopic total gastrectomy was performed. Pathological examination revealed a hamartomatous inverted polyp (HIP) in the submucosal layer with tub2-por1 tumor in the HIP. Prominent lymphocytic infiltration and OGCs were found around the tumor. Immunohistochemical analysis showed that the tumor cells were negative for EBER, MLH-1, and MSH2, 6. These findings suggest that this tumor was a non-microsatellite instability (MSI)-high GCLS without Epstein-Barr virus (EBV) infection. The patient's postoperative course was uneventful and she was discharged 11 days after surgery. She remains well 3 years after surgery.