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Introduction: Complete tumor resection with clear margins including adjacent organs is the treatment of choice for gastrointestinal stromal tumors (GISTs). However, true tumor invasion of adjacent organs has been reported to be rare. Concomitant distal pancreatectomy (DP) for suspected tumor infiltration is not infrequently performed during resection of large gastric GISTs. This study aims to determine the true frequency of adjacent organ involvement by large gastric GISTs with particular attention to the pancreas and compares the outcome after curative resection with and without a concomitant DP in order to determine if DP is truly necessary., Methods: A retrospective review of 37 patients who underwent curative resection of large (>or=10 cm) gastric GISTs was conducted., Results: Wedge resections were performed in 22, partial gastectomies in nine, and total gastrectomies in six patients. The median operative time was 180 min (range, 60-330 min), and the patients had a median postoperative stay of 8 days (range, 4-29 days). Overall, there were eight (22%) morbidities including two (5%) mortalities. Nineteen (51%) had concomitant adjacent organ resection, and these included 15 (41%) DPs with splenectomies. Direct organ invasion was demonstrated in 5/19 patients (26%) and 7/30 organs (23%) resected. Only 1/15 (6.7%) DP specimens demonstrated tumor infiltration. Comparison between the patients with and without a concomitant DP demonstrated that performance of a DP was associated with a longer operation time [225 min (range, 105-305 min) vs 158 min (60-330 min), P=.002)], increased postoperative stay [9 days (range, 7-29 days) vs 7.5 days (4-19 days), P=.042], and increased postoperative morbidity [6 (40%) vs 2 (9%), P=.025]. The DP cohort also had a statistically significant poorer 5-year recurrence free survival (22% vs 60%, P=.017)., Conclusion: Although adjacent organ involvement is not uncommon with large gastric GISTs, concomitant DP is usually unnecessary as direct pancreatic invasion is rare. Furthermore, concomitant DP with splenectomy is associated with an increase in postoperative morbidity.

Introduction: Gastrointestinal stromal tumors (GISTs) arising from outside the gut wall also termed extragastrointestinal stromal tumors (EGISTs) are reported to be rare. Presently, their pathogenesis remains controversial, and recently, it has been proposed that EGISTs may be the result of extensive extramural growth of GISTs which lose contact with the gut wall. This study presents a single-institution experience with eight EGISTs and compares their clinicopathological features with mural GISTs in order to determine further insight to their possible origin., Methods: Between 1997 and 2008, 156 patients with pathologically proven CD117-positive primary GISTs were retrospectively reviewed. Eight tumors were identified as EGISTs, 104 were gastric GISTs, and 44 were small-bowel GISTs. Mural GISTs were classified as extramural or intra/transmural according to their gross pattern of growth., Results: There were five male and three female patients with a median age of 58 years (range, 42-81 years). All patients were symptomatic, and the tumors were located in the greater omentum (n = 2), lesser sac (n = 2), lesser omentum, retroperitoneum, small-bowel mesentery, and pancreas. The median tumor size was 140 mm (range, 55 to 220 mm). Seven of eight EGISTs were found to be in close association to the adjacent gut wall. Pathological examination demonstrated that two tumors demonstrated focal involvement of the muscularis propria of the adjacent gut wall. Four tumors demonstrated tumor abutting or adherent to the serosa but no muscle involvement and one tumor was separated from the serosa. Comparison between the clinicopathological features of EGISTs with extramural GISTs and intra/transmural GISTs demonstrated that EGISTs were significantly larger [140 range (55-220) mm vs 80 (5-260) mm vs 50 (15-190) mm, P = 0.049, P < 0.001 respectively]., Conclusion: The occurrence of true EGISTs is rare. Most cases demonstrate some form of communication or contact with the gut wall, and EGISTs are significantly larger than extramural or intra/transmural GIST. These observations suggest that most, if not all, cases of EGISTs are likely to represent mural GISTs with extensive extramural growth with eventual loss of contact with the muscle layer of the gut.

Background: This study aims to validate and compare the performance of the National Institute of Health (NIH) criteria, Huang modified NIH criteria, and Armed Forces Institute of Pathology (AFIP) risk criteria for gastrointestinal stromal tumors (GISTs) in a large series of localized primary GISTs surgically treated at a single institution to determine the ideal risk stratification system for GIST., Methods: The clinicopathological features of 171 consecutive patients who underwent surgical resection for GISTs were retrospectively reviewed. Statistical analyses were performed to compare the prognostic value of the three risk criteria by analyzing the discriminatory ability linear trend, homogeneity, monotonicity of gradients, and Akaike information criteria., Results: The median actuarial recurrence-free survival (RFS) for all 171 patients was 70%. On multivariate analyses, size >10 cm, mitotic count >5/50 high-power field, tumor necrosis, and serosal involvement were independent prognostic factors of RFS. All three risk criteria demonstrated a statistically significant difference in the recurrence rate, median actuarial RFS, actuarial 5-year RFS, and tumor-specific death across the different stages. Comparison of the various risk-stratification systems demonstrated that our proposed modified AFIP criteria had the best independent predictive value of RFS when compared with the other systems., Conclusion: The NIH, modified NIH, and AFIP criteria are useful in the prognostication of GIST, and the AFIP risk criteria provided the best prognostication among the three systems for primary localized GIST. However, remarkable prognostic heterogeneity exists in the AFIP high-risk category, and with our proposed modification, this system provides the most accurate prognostic information.