Sporadic Gastrointestinal Stromal Tumors Research Articles

Gastrointestinal stromal tumors in Japanese patients with neurofibromatosis type I.

BackgroundNeurofibromatosis type I (NF1) predisposes patients to various neoplasias, including gastrointestinal stromal tumors (GISTs). Little is known about the risk of developing GISTs for NF1 patients or the clinicopathologic features and prognosis of NF1-GIST.MethodsWe conducted a multi-detector computed tomography screen for adult NF1 patients between 2003 and 2012. Clinicopathologic data of sporadic GISTs from patients who underwent surgery between 2001 and 2010 were retrospectively collected from 32 hospitals in Japan.ResultsCT screening identified 6 GIST patients from the 95 NF1 patients screened, suggesting that the prevalence rate of GISTs was approximately 6.3/100 in NF1 patients. All 6 NF1 patients exhibited hyperplasia of the interstitial cells of Cajal in the adjoining small intestine. NF1-GISTs may account for 1.1–1.3 % of primary sporadic GISTs and present as multiple tumors in the small intestine, with low mitotic activity and no KIT or PDGFRA mutations. The risk of recurrence and mortality is very similar between NF1 and non-NF1 patients after surgical resection of GISTs.ConclusionsNF1 patients may be predisposed to developing small intestinal GISTs, which may appear as multiple GISTs without KIT and PDGFRA mutations. The prognosis of patients with NF1-GISTs is similar to patients with conventional GISTs.Electronic supplementary materialThe online version of this article (doi:10.1007/s00535-015-1132-6) contains supplementary material, which is available to authorized users.

Aberrant DNA hypermethylation of SDHC: a novel mechanism of tumor development in Carney triad

Carney triad (CT) is a rare condition with synchronous or metachronous occurrence of gastrointestinal stromal tumors (GISTs), paragangliomas (PGLs), and pulmonary chondromas in a patient. In contrast to Carney–Stratakis syndrome (CSS) and familial PGL syndromes, no germline or somatic mutations in the succinate dehydrogenase (SDH) complex subunits A, B, C, or D have been found in most tumors and/or patients with CT. Nonetheless, the tumors arising among patients with CT, CSS, or familial PGL share a similar morphology with loss of the SDHB subunit on the protein level. For the current study, we employed massive parallel bisulfite sequencing to evaluate DNA methylation patterns in CpG islands in proximity to the gene loci of all four SDH subunits. For the first time, we report on a recurrent aberrant dense DNA methylation at the gene locus of SDHC in tumors of patients with CT, which was not present in tumors of patients with CSS or PGL, or in sporadic GISTs with KIT mutations. This DNA methylation pattern was correlated to a reduced mRNA expression of SDHC, and concurrent loss of the SDHC subunit on the protein level. Collectively, these data suggest epigenetic inactivation of the SDHC gene locus with Key Words

PDGFRA-mutant syndrome

Germline PDGFRA mutations cause multiple heterogeneous gastrointestinal mesenchymal tumors. In its familial form this disease, which was formerly termed intestinal neurofibromatosis/neurofibromatosis 3b (INF/NF3b), has been included among familial gastrointestinal stromal tumors (GISTs) because of its genotype, described when GIST was the only known PDGFRA-mutant gastrointestinal tumor. Shortly afterwards, however, inflammatory fibroid polyps also revealed PDGFRA mutations. Subsequently, gastrointestinal CD34+ ‘fibrous tumors’ of uncertain classification were described in a germline PDGFRA-mutant context. Our aim was to characterize the syndrome produced by germline PDGFRA mutations and establish diagnostic criteria and management strategies for this hitherto puzzling disease. We studied a kindred displaying multiple gastrointestinal mesenchymal tumors, comparing it with published families/individuals with possible analogous conditions. We identified a novel inherited PDGFRA mutation (P653L), constituting the third reported example of familial PDGFRA mutation. In adult mutants we detected inflammatory fibroid polyps, gastric GISTs and gastrointestinal fibrous tumors of uncertain nosology. We demonstrate that the syndrome formerly defined as INF/NF3b (exemplified by the family reported herein) is simplistically considered a form of familial GIST, because inflammatory fibroid polyps often prevail. Fibrous tumors appear variants of inflammatory fibroid polyps. ‘INF/NF3b’ and ‘familial GIST’ are misleading terms which we propose changing to ‘PDGFRA-mutant syndrome’. In this condition, unlike KIT-dependent familial GIST syndromes, if present, GISTs are stomach-restricted and diffuse Cajal cell hyperplasia is not observed. This restriction of GISTs to the stomach in PDGFRA-mutant syndrome: (i) focuses oncological concern on gastric masses, as inflammatory fibroid polyps are benign; (ii) supports a selective role of gastric environment for PDGFRA mutations to elicit GISTs, justifying the known predilection for stomach of sporadic PDGFRA-mutant GISTs. An awareness that inflammatory fibroid polyps, relatively common among gastrointestinal mesenchymal tumors, may be the prevailing tumor in PDGFRA-mutant syndrome could eventually reveal an unsuspected prevalence of this condition.

Gut wall replacing type of gastrointestinal stromal tumor presenting as a perforation of the ileal diverticulum

Gastrointestinal stromal tumors (GISTs) usually form a well-circumscribed mass. Very rarely, however, sporadic GISTs show gut-wall replacing growth, similar to the diffuse hyperplasia of interstitial cells of Cajal (ICC) observed in patients with neurofibromatosis type 1 (NF1) and hereditary GIST. Here we describe a patient with ileal perforation caused by this unusual type of GIST. An 82-year-old man was admitted to the emergency department with sudden abdominal pain. Following a provisional diagnosis of perforation of Meckel's diverticulum, he underwent segmental resection of the small intestine. Macroscopic examination revealed a diverticulum-like structure 2.5cm in size near the site of mesenteric attachment of the ileum. Histological examination showed diffuse and nodular proliferation of spindle cells positive for c-KIT and CD34 that had replaced the muscularis propria of the small intestine. Mutational analyses of the lesions revealed monoclonality of proliferating cells with a somatic mutation in c-kit exon 11 (p.Leu576Pro). Gut-wall replacing type of GIST should be recognized as a specific type of GIST causing diverticulum-like structures of the gastrointestinal tract.

A Sporadic Small Jejunal GIST Presenting with Acute Lower Gastrointestinal Hemorrhage: A Review of the Literature and Management Guidelines.

Gastrointestinal stromal tumors (GISTs) represent the majority of primary nonepithelial neoplasms of the digestive tract, most frequently expressing the KIT protein detected by immunohistochemical staining for the CD117 antigen. Jejunal GISTs account for approximately 10% of GISTs. Patients usually present with abdominal discomfort. Jejunal GISTs may cause symptoms secondary to obstruction or hemorrhage. Pressure necrosis and ulceration of the overlying mucosa may cause gastrointestinal bleeding, and patients who experience significant blood loss may suffer from malaise and fatigue. Literature has classified small-bowel GISTs on the basis of size, and various established guidelines have advised conservative management of small jejunal GISTs (<2cm). We here report the clinical, macroscopic, and immunohistological features of a small jejunal GIST presenting with acute lower gastrointestinal hemorrhage in a 50-year-old postmenopausal woman necessitating an emergency laparotomy to control the bleed. The management of very small (<2cm) small-bowel GISTs is controversial. While guidelines are primarily based on the risk of malignancy in GISTs, no guideline predicting the risk of complications in small-bowel GISTs exists. Hence, these tumors should be removed even if incidentally detected.

Gastrointestinal stromal tumors in the setting of multiple tumor syndromes.

Knowledge related to gastrointestinal stromal tumor (GIST) in the setting of nonhereditary and hereditary multiple tumor syndromes continues to expand. This review describes associations between sporadic GIST and second malignancies, as well as new contributions to our knowledge about hereditary GIST multiple tumor syndromes. Sporadic GIST patients have increased risk of developing synchronous/metachronous cancers, including nonhematologic and hematologic malignancies. Data suggest these associations are nonrandom, more prevalent in men and increase with age. New adrenal tumors have also been associated with nonhereditary Carney's triad. Meanwhile, understanding of the molecular basis of heritable GIST syndromes has improved. Several new familial GIST kindreds have been reported, including those with germline KIT and PDGFRα mutations. Knowledge about succinate dehydrogenase (SDH) deficiency and mutations in hereditary GIST syndromes has expanded. It is now known that neurofibromatosis-1-associated GISTs are SDHB-positive, whereas Carney-Stratakis syndrome-associated GISTs are SDHB-deficient with underlying germline mutations in SDH subunits A-D. Recognition and early diagnosis of GIST syndromes allows for improved comprehensive medical care. With additional understanding of the molecular pathogenesis of GIST multiple tumor syndromes, we can refine our screening programs and management of these patients and their families.

Multiple sporadic gastrointestinal stromal tumors concomitant with ampullary adenocarcinoma: A case report with KIT and PDGFRA mutational analysis and miR-221/222 expression profile

GISTs originating multifocally at different GI sites, in patients lacking familial syndromes, could be interpreted as recurrent/metastatic disease. MiR-221/222 have recently been identified as regulators of KIT expression in GISTs. We report the first case of synchronous GISTs in the stomach and duodenum concomitant with an ampullary adenocarcinoma. Different CD117 expression patterns could be related to different KIT mutational status in the two lesions: gastric GIST showed a dot-like pattern and lacked KIT mutations; duodenal GIST had a strong membranous expression pattern, likely due to KIT exon 9 duplication, which is associated with lower response to imatinib. MiR-221/222 were downregulated in GISTs as compared with normal tissue (p<0.05) and expressed increased levels in the gastric GIST as compared with duodenal one (p<0.05). Our data support an independent origin of the two GISTs. Determining whether these tumors are multiple primaries or recurrencies is helpful to predict their malignancy and to select proper treatment.

A subset of gastrointestinal stromal tumors previously regarded as wild-type tumors carries somatic activating mutations in KIT exon 8 (p.D419del)

About 10–15% of gastrointestinal stromal tumors (GISTs) carry wild-type sequences in all hot spots of KIT and platelet-derived growth factor receptor alpha (PDGFRA) (wt-GISTs). These tumors are currently defined by having no mutations in exons 9, 11, 13, and 17 of the KIT gene and exons 12, 14, and 18 of the PDGFRA gene. Until now, the analysis of further exons is not recommended. However, we have previously published a report on a KIT exon 8 germline mutation, which was associated with familial GIST and mastocytosis. We therefore investigated whether KIT exon 8 mutations might also occur in sporadic GIST. We screened a cohort of 145 wt-GISTs from a total of 1351 cases from our registry for somatic mutations in KIT exon 8. Two primary GISTs with an identical exon 8 mutation (p.D419del) were detected, representing 1.4% of all the cases analyzed. Based on all GISTs from our registry, the overall frequency of KIT exon 8 mutations was 0.15%. The first tumor originating in the small bowel of a 53-year-old male patient had mostly a biphasic spindled-epithelioid pattern with a high proliferative activity (14 mitoses/50 HPF) combined with a second low proliferative spindle cell pattern (4/50 HPF). The patient developed multiple peritoneal metastases 29 months later. The second case represented a jejunal GIST in a 67-year old woman who is relapse-free under adjuvant imatinib treatment. We conclude that about 1–2% of GISTs being classified as ‘wild type’ so far might, in fact, carry KIT mutations in exon 8. Moreover, this mutational subtype was shown to be activating and imatinib sensitive in vitro. We therefore propose that screening for KIT exon 8 mutations should become a routine in the diagnostic work-up of GIST and that patients with an exon 8 mutation and a significant risk for tumor progression should be treated with imatinib.

Gastrointestinal stromal tumor associated with neurofibromatosis type I.

10539 Background: Most gastrointestinal stromal tumors (GIST) have either KIT or PDGFRA mutations. Neurofibromatosis type 1 pts caused by mutations in the NF1 gene have increased risk of GIST development, which may have no mutation in both genes. In this study, we analyzed clinical and pathological features of NF-1 associated GISTs. Methods: Study 1: We have screened 95 adults NF1 pts (age 31-66, 35 male and 60 female) by enhanced MDCT between 2003 and 2012. Study 2: We collected 1,184 sporadic GISTs from community hospitals in Japan between 2001 and 2010 retrospectively, and found 24 primary NF1-GISTs (1.7% of sporadic) and 2 recurrent NF1-GISTs, of whom clinicopathological features were analyzed. Results: Study1: By MDCT screening, we have found histologically confirmed 6 GISTs (4 males and 2 female; 6/1,000 NF1-persons/year) in the small intestine. Median age of NF1-GIST was 45, and five pts had multiple tumors, ICC hyperplasia in the normal intestine and no mutation in the KIT and PDGFRA genes. Study 2: Median age of 26 NF1-GIST (12 male and 14 female) was 58. 25 GISTs were located in the small bowel and one in the stomach. 17 pts had multiple GISTs and 9 pts single lesion. Pathologically, KIT was positive for all NF1-GISTs. 24 pts had spindle cell tumors and 2 had mixed or epithelioid. No mutation was found in the KIT and PDGFRA genes of 11 pts examined. Median values of mitosis (0/50HPF) and Ki67 (0.5%) were lower than those of sporadic GIST (3/50HPF and 2.5%). With media follow-up of 3.6 years, 8 pts had recurrences and 4 pts died of the disease. By western blotting, KIT was faintly phosphorylated but its downstream kinases including MEK, p44/22, AKT, mTOR, p38 and STAT3, were activated. Six pts received imatinib and had no response and, subsequently, 5 pts received sunitinib with 4 PD and 1 short-term SD. Conclusions: NF1-associated GIST is a rare entity of GIST and has distinctive features from conventional sporadic GISTs. KIT-targeted TKI appeared to be ineffective to recurrent and advanced NF1-GISTs.

Molecular characterization of an Italian series of sporadic GISTs

Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors of the gastrointestinal tract. Most (80 %) contain activating mutations in the KIT receptor tyrosine kinase, roughly 10 % in platelet-derived growth factor receptor-alpha (PDGFRA). In a small subset, BRAF mutations are an alternative molecular pathway. GISTs respond well to imatinib, but low response is seen in patients with wild-type KIT or PDGFRA. Resistance has also been reported as a result of mutations in downstream effectors such as BRAF. We provide here a molecular characterization of a series of primary GISTs from Italian patients. Of 121 GIST cases diagnosed between 2000 and 2012, 83 were evaluated by PCR amplification and direct sequencing for mutations in KIT exons 8, 9, 11, 13, and 17, PDGFRA exons 12, 14, and 18, and BRAF exon 15. Eighty-one GISTs also underwent K-RAS testing. Sixty-four GISTs were positive: 55 had mutations in KIT and 9 in PDGFRA; 16 patients were mutation negative. Three samples came from NF1 patients and were KIT- and PDGFRA negative. Overall, we identified six novel mutations in KIT (p.K550_M552delinsL, p.Q556_W557delinsG p.Q556_G575del, p.W557_V559delinsQ p.P573_R588dup, p.G592_K593dup) and one novel mutation in PDGFRA (p.D842_N848delinsVDV), thus contributing to widening the spectrum of known mutations in GIST tumors and confirming the most frequently altered regions underlying GIST development. Among the 64 KIT- and PDGFRA-positive sporadic patients in our series, no BRAF or KRAS mutations were identified, suggesting that co-occurrence of these mutations is likely to be rare in the northwestern Italian population and not a frequent cause of primary resistance to imatinib in KIT-positive GIST patients.

Gastrointestinal Stromal Tumors Associated with Neurofibromatosis 1: A Single Centre Experience and Systematic Review of the Literature Including 252 Cases

Aims. The objectives of this study were (a) to report our experience regarding the association between neurofibromatosis type 1 (NF1) and gastrointestinal stromal tumors (GISTs); (b) to provide a systematic review of the literature in this field; and (c) to compare the features of NF1-associated GISTs with those reported in sporadic GISTs. Methods. We reported two cases of NF1-associated GISTs. Moreover we reviewed 23 case reports/series including 252 GISTs detected in 126 NF1 patients; the data obtained from different studies were analyzed and compared to those of the sporadic GISTs undergone surgical treatment at our centre. Results. NF1 patients presenting with GISTs had a homogeneous M/F ratio with a mean age of 52.8 years. NF1-associated GISTs were often reported as multiple tumors, mainly incidental, localized at the jejunum, with a mean diameter of 3.8 cm, a mean mitotic count of 3.0/50 HPF, and KIT/PDGFRα wild type. We reported a statistical difference comparing the age and the symptoms at presentation, the tumors' diameters and localizations, and the risk criteria of the NF1-associated GISTs comparing to those documented in sporadic GISTs. Conclusions. NF1-associated GISTs seem to have a distinct phenotype, specifically younger age, distal localization, small diameter, and absence of KIT/PDGRFα mutations.

Behavior of advanced gastrointestinal stromal tumor in a patient with von-Recklinghausen disease: Case report

Gastrointestinal stromal tumors (GISTs) represent a malignant gastrointestinal tumor of neurofibromatosis type 1 (NF1) Von Recklinghausen disease. In the current case, we report a 27-year-old woman with NF1, who presented with a lower abdominal mass, symptomatic anaemia, and significant weight loss. We employed multiple approaches to assess the tumor behavior, including computed tomography (CT) scan, surgical tumor resection, histological and immunohistochemical analysis and gene sequencing. Additionally, the patient was given Imatinib mesylate (Gleevec) as adjuvant therapy. CT scan delineated a large thick wall cavity lesion connecting to the small bowel segment. Resection of the tumor yielded a mass of 17 cm × 13 cm with achievement of safety margins. The diagnosis was GIST, confirmed by immunohistochemical expression of CD117, CD34, and Bcl-2. Sequencing revealed no mutations in either KIT or platelet-derived growth factor receptor-alpha, genes which are mutated in over 85% of sporadic GIST cases. Further, there was no evidence of recurrence, metastasis or metachronous GIST for over three years in our patient. From our analyses, we believe selective genotyping is advisable for high risk patients to predict potential tumor behavior.

Expression of the Receptor for Type I Insulin-like Growth Factor (IGF1R) in Gastrointestinal Stromal Tumors

A majority of gastrointestinal stromal tumors (GISTs) carry gain-of-function KIT or platelet-derived growth factor receptor α (PDGFRA) mutations. However, no mutational activation of KIT or PDGFRA has been identified in pediatric gastric GISTs, neurofibromatosis-1-associated GISTs, and a small subset of sporadic GISTs in adults [so-called wild-type (WT) GISTs]. Recently, pediatric gastric GISTs and some adult WT gastric GISTs have been found to have losses of the succinate dehydrogenase (SDH) complex, a Krebs cycle/electron transport chain interface protein, as seen by immunohistochemical loss of SDH subunit B (SDHB) expression. Moreover, recently, expression of the receptor for type I insulin-like growth factor (IGF1R) has been detected in pediatric and WT GISTs, although only a small number of cases have been analyzed. In this study, IGF1R expression was examined immunohistochemically in 1078 well-characterized GISTs representing different clinicogenetic categories and in 103 non-GIST gastrointestinal tumors. IGF1R expression was detected in 71/80 of SDH-deficient GISTs (SDHB-negative GISTs) but only in 9/625 (1%) of the SDHB-positive gastric GISTs. The latter often carried KIT or PDGFRA mutations and generally occurred in older patients. None of the 373 intestinal GISTs was IGF1R positive, whereas many primary intestinal sarcomas, including clear cell sarcomas, leiomyosarcomas, and undifferentiated sarcomas, were IGF1R positive. The consistent lack of IGF1R expression in intestinal GISTs should be considered an additional immunohistochemical marker in the differential diagnosis between GISTs and non-GIST sarcomas. Because inhibition of IGF1R signaling might become a therapeutic target in GISTs, screening for IGF1R expression may become important in the near future.

Expression of IGF-1 Receptor in KIT/PDGF Receptor-α Wild-Type Gastrointestinal Stromal Tumors with Succinate Dehydrogenase Complex Dysfunction

KIT/PDGF receptor-α (PDGFRA) wild-type (WT) gastrointestinal stromal tumors (GIST) are characterized by an overexpression of IGF-1 receptor (IGF1R) at the mRNA and protein level. More recently, germline and somatic mutations in succinate dehydrogenase (SDH) subunits A, B and C have been identified in KIT/PDGFRA WT sporadic GIST. Until now, the molecular basis of IGF1R overexpression in KIT/PDGFRA WT GIST has not been explained. In this brief report we investigate the status of the SDH complex at the genomic and protein level in relation to IGF1R expression at the mRNA and protein level in seven KIT/PDGFRA WT sporadic GIST patients. We found that IGF1R was upregulated in all patients harboring SDH mutations or displaying a SDH dysfunction, with respect to KIT/PDGFRA WT GIST without SDH mutations. Western blot analysis confirmed that all patients with an upregulation of IGF1R mRNA had detectable IGF1R protein expression. This report would suggest that IGF1R overexpression in KIT/PDGFRA WT GIST could be driven by the loss-of-function of the SDH mitochondrial complex.

Translationale Forschung und Diagnostik bei GIST

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors in the digestive tract. In up to 90% of cases, they are characterized by activating mutations in the KIT or the PDGFRA gene. GIST represent a paradigm for successful targeted treatment with tyrosine kinase inhibitors (TKI). Since the approval of the TKI imatinib in 2002 the survival of patients with metastatic GIST has tripled. The next logical step was the concept of using imatinib in an adjuvant approach, which was recently shown to increase overall survival significantly. In both settings, the mutational status has high predictive implications. In detail, GIST with KIT exon 11 mutations show the best response rates with partial remission rates of up to 80%. In KIT exon 9 mutations, a doubled daily dose of 800 mg imatinib is now standard. The PDGFRA exon 18 mutation D842V has been shown to lead to primary resistance. The treatment strategy in GIST is driven by their molecular characterisation. Further research has increased our knowledge on resistance mechanisms in solid tumors against TKI. The number of patients with secondary resistance due to acquired KIT mutations is increasing with treatment duration. Strategies to address this situation are the introduction of novel pathway inhibitors targeting different levels of signal transduction pathways, such as the mTOR/Akt pathway, the RAS/RAF pathway, histone deacetylation, among others. Among the GIST without mutations in the common hot spot regions of KIT and PDGFRA, the so-called wildtype GIST, further genomic subgroups have been identified. One such subgroup carries inactivating germline mutations in the genes encoding succinate dehydrogenase B, C, or D. They are associated with the occurrence of paragangliomas, so-called Carney-Stratakis syndrome. Most frequently, these GIST are located in the stomach, showing an epithelioid phenotype and a multinodular growth pattern. They preferentially occur in young females and often show lymph node metastases, the latter being very unusual in sporadic GIST. In sporadic Carney's triad additional pulmonary chondromas are observed and there are no SDH mutations. Another small subgroup of sporadic GIST present with BRAF mutations as an alternative genomic event. Finally, very rare kindreds with germline mutations in either KIT or PDGFRA have been described who develop multiple GIST and depending on the mutational subtype mastocytosis, hyperpigmentation and/or dysphagia. In summary, the molecular characterisation of GIST has revolutionized their treatment due to increasing knowledge about the high relevance of predictive molecular typing in solid tumors.

Molecular alterations and expression of succinate dehydrogenase complex in wild-type KIT/PDGFRA/BRAF gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract, disclosing somatic KIT, PDGFRA and BRAF mutations. Loss of function of succinate dehydrogenase (SDH) complex is an alternative molecular mechanism in GISTs, namely in carriers of germline mutations of the SDH complex that develop Carney-Stratakis dyad characterized by multifocal GISTs and multicentric paragangliomas (PGLs). We studied a series of 25 apparently sporadic primary wild-type (WT) KIT/PDGFRA/BRAF GISTs occurring in patients without personal or familial history of PGLs, re-evaluated clinicopathological features and analyzed molecular alterations and immunohistochemistry expression of SDH complex. As control, we used a series of well characterized 49 KIT/PDGFRA/BRAF-mutated GISTs. SDHB expression was absent in 20% and SDHB germline mutations were detected in 12% of WT GISTs. Germline SDHB mutations were significantly associated to younger age at diagnosis. A significant reduction in SDHB expression in WT GISTs was found when compared with KIT/PDGFRA/BRAF-mutated GISTs. No significant differences were found when comparing DOG-1 and c-KIT expression in WT, SDHB-mutated and KIT/PDGFRA/BRAF-mutated GISTs. Our results confirm the occurrence of germline SDH genes mutations in isolated, apparently sporadic WT GISTs. WT KIT/PDGFRA/BRAF GISTs without SDHB or SDHA/SDHB expression may correspond to Carney-Stratakis dyad or Carney triad. Most importantly, the possibility of PGLs (Carney-Stratakis dyad) and/or pulmonary chondroma (Carney triad) should be addressed in these patients and their kindred.

Expression of Podoplanin is a Rare Event in Sporadic Gastrointestinal Stromal Tumors and Does Not Influence Prognosis

Podoplanin overexpression is associated with worse prognosis in several human cancers. In gastrointestinal stromal tumors (GISTs) very few data on the expression of podoplanin exist, but it seems to be frequently overexpressed in pediatric/syndromic GISTs. We investigated podoplanin expression and its clinical relevance in a large series of sporadic GISTs. Podoplanin expression was determined immunohistochemically in 145 sporadic adult GISTs. Aneuploidies of 1p36 and 1q25 were investigated using FISH, and KIT and PDGFRA genes were investigated by sequencing. Overexpression of podoplanin was observed in eight (5.6%) GISTs and no association with amplification of 1p36 or KIT or PDGFRA mutations was seen. The amount of podoplanin expression was not associated with clinical risk factors or patient survival. Overexpression of podoplanin is a rare event in sporadic GISTs and is not associated with amplification of 1p36 or with KIT or PDGFRA mutations, which indicates limited pathobiological or clinical relevance.

EComment. Gastrointestinal stromal tumours

We would like to comment on the case report by Kim and colleagues concerning the surgical treatment of a gastrointestinal stromal tumour in the posterior mediastinum [1]. Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the gastrointestinal tract (5000 new cases per year in the United States) [2]. They can be found in patients with a median age of 60 y, with frequent occurrence (70%) in the muscular wall of the stomach, followed by small bowel (10-20%), oesophagus, omentum, mesentery and retroperitoneum [2,3]. GISTs can range from small benign tumours to sarcomas at all sites of occurrence. Tumours that have metastasized at presentation have a very poor prognosis. The 5-year survival in patients with malignant GISTs is less than 40% [2]. There are three key prognostic factors: mitotic rate, tumour size, and site. Tumours that are small (=2 cm) and show mitotic activity not exceeding 5 mitoses per 50 high-power fields, have an excellent prognosis. This prognosis probably is independent of site, although this has not been shown specifically for all sites. In the stomach, most epithelioid GISTs are benign. However, we have to bear in mind that a small proportion of tumours apparently lacking mitotic activity do metastasize [2,3]. GISTs in association with paragangliomas and pulmonary chondromas constitute the Carney triad. In fact, the ‘Carney triad’ is a multiple neoplasia syndrome affecting mostly females. This syndrome - or Carney complex - predisposes to a variety of tumours including adrenocortical adenomas (unilateral or bilateral) that are usually non-functioning [2,4]. Carney and Stratakis, in 2002, distinguished the inherited GISTs with paraganglioma syndrome from the Carney triad as an autosomal dominant condition in adult patients. This condition has been called Carney-Stratakis syndrome [5]. These two syndromes, even though quite rare, have entered the realm of multiple endocrine neoplasias in the last years. Carney-Stratakis syndrome is probably more frequent and may be prevalent amongst patients with GISTs that are negative for KIT/PDGFRA mutations [2]. A high index of suspicion is required by surgeons who are dealing with patients with isolated or sporadic GISTs or paragangliomas. They have to be aware of the Carney and Carney-Stratakis syndromes. A multidisciplinary diagnostic approach regarding the medical and family history of the patients is of paramount importance (especially in the younger patient with KIT or PDFGRA mutation-negative GISTs) [2]. Conflict of Interest: None declared

Multicentric gastrointestinal stromal tumor of the stomach with wild-type KIT and PDGFRA

Gastrointestinal stromal tumors (GISTs) are usually solitary tumors, mostly situated in the stomach and proximal small intestine. The existence of multiple lesions is thought to be an unusual event in some specific circumstances. Synchronous lesions are commonly viewed as the result of metastatic GIST, especially when the tumors are very different from each other in size and smaller lesions are located on the omentum or peritoneum. Nevertheless, differential diagnosis should include multiple primary sporadic GIST. Here we report a rare sporadic metachronous double GIST of the stomach; both tumors lacked KIT and PDGFRA mutations. The 76-year-old male underwent wedge resection of both gastric tumors and was treated postoperatively with imatinib 400 mg daily. He remained recurrence-free after 20 months of follow-up.

Identification of SDHA (subunit A of the succinate dehydrogenase) mutations in KIT/PDGFRA WT gastrointestinal stromal tumors (GISTs).

10045 Background: About 10%-15% of GISTs do not harbour KIT/PDGFRA mutations (wild-type, WT). We analyzed the tumor transcriptome of two sporadic young adults WT GISTs patients using massively para...