Dose pathological uniformity exist between center and periphery of gastric gastrointestinal stromal tumors?

Abstract

Gastrointestinal stromal tumors (GISTs) have been reported increasingly and are currently regarded as potentially malignant tumors. So, the risk stratification in patients with GISTs will be important to manage. According to the risk stratification of Armed Forces Institute of Pathology (AFIP) criteria and National Institutes of Health consensus criteria, mitotic index has been known as one of most important factors to predict of behavior of cells in GISTs. Mitosis identification needs to be interpreted carefully because it can be subjective according to pathologists or measurement sites, and it remains unknown where to measure the mitotic index. Therefore, the aim of this study was to identify the pathological uniformity of mitotic counts between the periphery and center of the lesions in gastric GISTs.

We analysis 37 patients received curative surgical resection for gastric GISTs at Hanyang University Seoul Hospital and reviewed pathological and clinical data retrospectively. Surgical resection was performed for patients with gastric GISTs larger than 2 cm. Pathological diagnosis was based on histopathology and immunohistochemical analysis. We categorized according to modified NIH criteria and the modified Armed Forces Institute of Pathology (AFIP) risk classification criteria. GIST centers were defined as a part of the tumor starting at 5 mm from the surface of the tumor. Mitotic index was counted under 50 high-power fields HPF and at 3 different sites of tumor.

The mean size of tumor was 3.56 ± 2.10 (range 2.0-11.5) cm, and 32 (86.5%) had a size of 2 to 5 cm. Gastric body was the most common involving site (n=14, 37.8%), followed by fundus (n=11, 29.7%), cardia (n=9, 24.3%) and antrum (n=3, 8.1%). The mitotic count was ≤ 5/50 HPF in 29 cases (78.4%), 6-10/50 HPF in 3 cases (8.1%), and > 10/HPF in 5 cases (13.5%). The original risk stratification by AFIP criteria showed that 3 cases were no risk, 22 very low risk, 1 low risk, 8 moderate risk and 3 high risk. Among 37 gastric GISTs, 94.6% (n=35) showed the same risk stratification for the center and the periphery. Only two (5.4%) cases had different risk stratification between the two sites. One case categorized into very low risk on center, while intermediate risk on periphery and original pathologic data.

This study indicated that mitotic indices of the periphery and center of gastric GISTs showed good concurrence. Therefore biopsy using endoscopic approaches will be representing whole gastric GISTs mass although it has limitation because of small l tissue volume and difficulty to approach the tumor.