OBJECTIVETo evaluate the clinicopathologic features of gastrointestinal stromal tumor (GIST) with synchronous carcinoma and the treatment principle.

METHODSNineteen cases of GIST with synchronous carcinoma were collected from 113 cases of GIST from 2002 to 2008. The clinicopathologic features were studied and the expression of CD117, CD34, smooth muscle actin and S-100 protein were detected by immunohistochemistry using EliVision method. The expression of proliferation marker Ki-67 was also studied. GIST with synchronous carcinoma and those without carcinoma were compared.

RESULTSNineteen cases (16.8%) of GIST with synchronous carcinoma were found, including 11 males and 8 females (male to female ratio 1.38: 1.00). The age of the patients ranged from 43 to 66 years (median age 57 years). Five of 19 cases were located in the inferior segment of esophagus and 14 were in the gastric wall. The diameter ranged from 0.6 to 3.8 cm [mean (1.91 ± 0.92) cm]. Three of 19 cases showed low grade dysplasia, and there was no dysplasia in the remaining 16 cases. The number of mitosis ranged from 0 to 4/50 HPF [mean (0.74 ± 1.07)/50 HPF]. The Ki-67 proliferative index (number of Ki-67 positive cell/HPF) ranged from 0 to 7.72% [mean (2.51 ± 2.20)%]. The synchronous carcinomas included two esophageal carcinomas and 17 gastric cancers.In contrast, patients of GIST without carcinoma included 52 males and 42 females (male to female ratio 1.24: 1.00). The age of patients ranged from 43 to 71 years (median age 55 years). Seventy-nine of the 94 cases were located in the stomach, 10 were in the intestine and 5 were in the esophagus. The diameter ranged from 2.4 to 15.5 cm [mean (5.42 ± 6.17) cm].Seventy-nine of the 94 cases showed variable degrees of dysplasia, and 12 cases were of high malignant potential. The number of mitosis ranged from 0 to 53/50 HPF [average (3.78 ± 10.22)/50 HPF]. The Ki-67 proliferative index ranged from 0 to 37.54% [mean (6.78 ± 12.45)%]. Comparing these two groups, the male to female ratio of GIST with synchronous carcinoma was higher than that of GIST without carcinoma. The average diameter of GIST with synchronous carcinoma was smaller than of those without carcinoma. The number of mitosis and Ki-67 proliferative index of GIST with synchronous carcinoma were significantly lower than those without carcinoma (t' = 2.809, P < 0.05; t' = 3.095, P < 0.05, respectively).

CONCLUSIONSSixteen point eight percent of GIST may be associated with synchronous carcinoma. There are no special clinical symptoms in most of GIST with synchronous carcinoma, as these GIST are usually incidental findings. The Ki-67 proliferative index of GIST with synchronous carcinoma is significantly lower than that of GIST without synchronous carcinoma. Most GIST with synchronous carcinoma can be treated by the standard treatment for the accompanying carcinoma, and do not require specific additional treatments.