Gastrointestinal stromal tumor: clinicopathological characteristics and pathologic prognostic analysis

OBJECTIVE: This study aimed to understand clinicopathological characteristics of gastrointestinal stromal tumors (GISTs) and correlation between pathologic features and clinical outcome. METHODS: We used 76 cases diagnosed as primary GISTs during January 2007 to July 2017 at Army Institute of Pathology, Thailand. Clinical, survival, and pathological data were collected and analyzed. RESULTS: Ages of the patients ranged from 15 to 88 years (M:F = 1:1). The most common presentation was gastrointestinal bleeding (39.7%). The most common site was the stomach (64.5%). Tumor size ranged from 0.6 to 25.5 cm (average 8.78 cm). Histologic types were spindle cell type (75%), mixed spindled-epithelioid type (17.1%), and epithelioid type (7.9%). The majority of histologic subtype was diffuse hypercellularity (67.1%). Tumor necrosis was found in 38.1% and 80% showed low mitotic counts. Most gastrointestinal stromal tumors (27.6%) are low-risk category according to Miettinen and Lasota’s algorithm. Metastasis was found in 27.7%, mostly occurs within 2 years, and is correlated with tumor size > 10 cm (P = 0.023), non-spindle cell histologic type (P = 0.027), mitotic count > 5/5mm(2) (P = 0.000), myxoid change (P = 0.011), and mucosal invasion (P = 0.002). Recurrence was found in 8.1%, mostly occurs within 7 years, and correlated with myxoid change (P = 0.045). CONCLUSION: We found that most of GISTs show spindle cell type and low-risk category. Metastasis was correlated with tumor size > 10 cm, non-spindle cell histologic type, mitotic count > 5/5mm(2), myxoid change, and mucosal invasion. Recurrence was correlated with myxoid change.