Primary gastric inflammatory myofibroblastic tumor: a clinicopathologic and immunohistochemical study of 5 cases.

Primary gastric inflammatory myofibroblastic tumors are rare. Here we report on 5 such cases (4 males and 1 female, age range 36-45 years). Their presenting symptoms included abdominal mass (5 patients), abdominal pain (4 patients), and upper gastrointestinal hemorrhage (1 patient). Tumor size ranged from 4.5 to 8 cm in the greatest dimension. Histologically, these tumors showed three patterns: myxoid hypocellular, fascicular, and hyalinized. A lymphoplasmacytic infiltrate was present in all 5 tumors. One to two mitotic figures were recognized in 10 high power fields (HPFs) in 4 patients and focally up to 5 in 10HPFs in 1 patient. No prominent nuclear atypia or necrosis was observed. ALK, smooth muscle actin, and vimentin staining were observed in all tumors. One tumor focally expressed desmin. S-100, CD21, CD34, CD35, CD68, and CD117 were negative in all IMTs. The patients were followed up for 2-5 years (mean 3.4 years), and none of them had tumor metastasis or died. Only one patient developed local recurrence and is now alive with no evidence of disease after the second surgery (11 months after the second surgery). Our results indicate that primary gastric IMTs have an intermediate behavior as seen at other sites.