BackgroundAbout 10–15% of adult, and most pediatric, gastrointestinal stromal tumors (GIST) lack mutations in KIT, PDGFRA, SDHx, or RAS pathway components (KRAS, BRAF, NF1). The identification of additional mutated genes in this rare subset of tumors can have important clinical benefit to identify altered biological pathways and select targeted therapies.MethodsWe performed comprehensive genomic profiling (CGP) for coding regions in more than 300 cancer-related genes of 186 GISTs to assess for their somatic alterations.ResultsWe identified 24 GIST lacking alterations in the canonical KIT/PDGFRA/RAS pathways, including 12 without SDHx alterations. These 24 patients were mostly adults (96%). The tumors had a 46% rate of nodal metastases. These 24 GIST were more commonly mutated at 7 genes: ARID1B, ATR, FGFR1, LTK, SUFU, PARK2 and ZNF217. Two tumors harbored FGFR1 gene fusions (FGFR1–HOOK3, FGFR1–TACC1) and one harbored an ETV6–NTRK3 fusion that responded to TRK inhibition. In an independent sample set, we identified 5 GIST cases lacking alterations in the KIT/PDGFRA/SDHx/RAS pathways, including two additional cases with FGFR1–TACC1 and ETV6–NTRK3 fusions.ConclusionsUsing patient demographics, tumor characteristics, and CGP, we show that GIST lacking alterations in canonical genes occur in younger patients, frequently metastasize to lymph nodes, and most contain deleterious genomic alterations, including gene fusions involving FGFR1 and NTRK3. If confirmed in larger series, routine testing for these translocations may be indicated for this subset of GIST. Moreover, these findings can be used to guide personalized treatments for patients with GIST. Trial registration NCT 02576431. Registered October 12, 2015Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-1075-6) contains supplementary material, which is available to authorized users.

Background/AimsGastric glomus tumors are extremely rare, and presurgical confirmation is often impossible. The identification of clinical and radiologic characteristics of this tumor type is important for preoperative diagnosis and treatment planning.MethodsIn this study, we analyzed 10 cases of gastric glomus tumors resected at a single institute over 9 years.ResultsEight of the patients were men and 2 were women, with a mean age of 49 years. Five patients presented with abdominal discomfort or pain, 1 presented with anemia, and the remaining 4 cases were found incidentally during endoscopic examinations. The most common location of the tumor was the antrum (n=7), followed by the low (n=2) and high body (n=1). Although the endoscopic ultrasonography findings were variable, contrast-enhanced computed tomography generally showed a strong homogeneous enhancement. The resected tumors were well-demarcated solid masses with sizes ranging from 1.0 to 3.6 cm. Microscopically, the masses were composed of abundant vascular channels with clusters of uniform and round glomus cells. There was no evidence of recurrence after complete surgical resection.ConclusionsGastric glomus tumors are unusual, distinct lesions that should be considered in the differential diagnosis of a gastric submucosal mass. Unlike their deep soft tissue counterparts, most glomus tumors in the stomach are benign.

Pathological diagnosis of gastrointestinal stromal tumors (GISTs) is based on histological findings and immunohistochemical demonstration of the KIT protein. KIT-negative GISTs account for B5% of cases and cause diagnostic difficulties. In the era of imatinib therapy, a correct diagnosis of GISTs is important for therapeutic reasons regardless of KIT expression. Recently, DOG1 has been introduced as an important diagnostic marker with high sensitivity and specificity. In this study, immunohistochemical staining for DOG1 and protein kinase C-h (PKC-h) in whole tissue sections, and mutation analyses for KIT and PDGFRA were performed in 26 KIT-negative GISTs. Tissue microarrays of 112 KIT-positive GISTs were used as controls. Overall, 25 KIT-negative GISTs were located in the stomach, and 1 in the rectum. The histological subtype was spindle in 12, epithelioid in 11, and mixed in 3 cases. The expression of DOG1 and PKC-h was positive in 24 (92%) and in 25 cases (96%), respectively. All 26 KIT-negative GISTs expressed either DOG1 or PKC-h, and 23 cases (89%) were positive for both makers. PKC-h was positive in two cases (8%), which lacked both KIT and DOG1 expressions. Mutation analysis showed PDGFRA exon 18 mutation in 15 cases (58%) and KIT exon 11 mutation in 1 case (4%), whereas the remaining 10 cases (39%) were wild type for both KIT and PDGFRA. The expression of DOG1 and PKC-h showed no significant difference in KIT-negative and KIT-positive GISTs (P ¼ 1.000 and P ¼ 0.167, respectively). Our findings suggest that both DOG1 and PKC-h can be used in the diagnosis of KIT-negative GISTs and they show positive staining even in KIT-negative tumors, which are wild type for KIT and PDGFRA on mutation analysis.