Gastrointestinal Mesenchymal Tumors Research Articles

Gastrointestinal schwannomas: a rare but important differential diagnosis of mesenchymal tumors of gastrointestinal tract

BackgroundSchwannomas of gastrointestinal tract are rare, mostly benign and notably different neoplasms from conventional schwannomas that arise in soft tissue or the central nervous system. These tumors are of clinical importance since they should always be considered in the differential diagnosis of submucosal lesions of gastrointestinal tract.MethodsSeven patients with a pathologically proven gastrointestinal schwannoma were identified in our series of mesenchymal tumors and reviewed retrospectively. Clinicopathological and immunohistochemical parameters along with the follow-up results were analysed.ResultsThe series included two males and five females, with a mean age 69 years (range, 39–81). Most patients were asymptomatic on presentation, except for two patients with abdominal pain. In the other cases (n = 5), the tumor was an incidental finding during other medical, imaging or surgical procedures. The tumors were located in the stomach (n = 4) and in the small intestine (n = 3) with an average size of 29 mm (range, 12–70). A preoperative diagnosis was achieved only in one case with a CT-guided core biopsy. Otherwise the clinical, intraoperative, endoscopic or radiological findings were unspecific. Patients with gastric tumor underwent either laparoscopic (n = 2) or open (n = 2) gastric wedge resection of the tumor; in the cases of intestinal tumor (n = 3) a segmentectomy was performed. Pathological examination revealed solid homogenous tumors, which were highly cellular and composed of spindle cells with positive staining for S100 protein, and confirmed the diagnosis of schwannoma. All tumors were negative for c-Kit, smooth muscle actin, desmin and DOG-1 and showed very low proliferation index. There were negative resection margins and no malignant variants were recognized. At an average follow-up of 60 months (range, 24–185) all patients were free of disease with no signs of recurrence or metastases and acceptable gastrointestinal function.ConclusionsSchwannomas are rare, slow-growing and mostly asymptomatic gastrointestinal mesenchymal tumors. They are difficult to be diagnosed preoperatively as endoscopic and radiological findings are nonspecific but histological and immunohistochemical features are of paramount importance to differentiate between benign and malignant schwannomas, or other spindle cell sarcomas. The treatment of choice is complete surgical excision without a conclusive preoperative diagnosis, and the long-term outcome is excellent as these lesions are mostly benign.

Differential diagnosis of gastrointestinal stromal tumor by histopathology and immunohistochemistry.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the gastrointestinal (GI) tract. GISTs account for approximately 80% of the clinically relevant GI mesenchymal tumors. Although most GISTs show spindle cell morphology, 10-15% of GISTs show pure epithelioid configuration. Therefore, not only spindle cell tumors but also epithelioid cell ones developing in the GI tract are subject to the differential diagnoses of GISTs. GISTs are basically positive for KIT, a receptor tyrosine kinase (RTK) encoded by protooncogene c-kit, by immunohistochemistry, but approximately 5% of GISTs are only weakly or barely positive for KIT. Since almost all spindle cell type GISTs are strongly and diffusely positive for KIT regardless of different genetic subtypes, diagnosis of the spindle cell type GISTs is not difficult. On the other hand, epithelioid cell type GISTs show different staining patterns of KIT in different genetic backgrounds. Approximately half of the epithelioid cell type GISTs with platelet-derived growth factor receptor alpha (PDGFRA) gene mutation might show weak or undetectable staining of KIT. On the other hand, almost all GISTs are negative for desmin, which is a positive marker for mature smooth muscle cells, and S100 protein, which is a Schwann cell marker. Smooth muscle tumors such as leiomyomas and leiomyosarcomas, which usually show the spindle cell morphology, consist of approximately 10% of the clinically relevant GI mesenchymal tumors and are almost positive for desmin and negative for KIT and S100 protein. Schwannomas which nearly always show the spindle cell pattern, comprise up to 5% of the GI mesenchymal tumors, and almost all of them are positive for S100 protein and negative for KIT and desmin. Thus, most GI mesenchymal tumors are differentially diagnosed by immunohistochemistry (IHC) of KIT, desmin and S100 protein. However, mesenchymal tumors such as desmoids, solitary fibrous tumors (SFTs), inflammatory myofibroblastic tumors (IMTs), perivascular epithelioid cell tumors (PEComas), inflammatory fibroid polyps (IFPs), rarely develop in the GI tract, and have to be correctly diagnosed through detection of specific immunohistochemical markers and/or unique genetic aberrations.

Clinicopathologic features of gastric plexiform fibromyxoma

Objective: To analyse the clinicopathologic features of gastric plexiform fibromyxoma (PF) including diagnosis, differential diagnosis, immunohistochemistry and molecular pathology. Methods: Eight cases of PF were collected from June 2006 to June 2017 at the Second Affiliated Hospital of Zhengzhou University and the First Affiliated Hospital of Zhengzhou University. The clinicopathologic findings of eight cases of PF were retrospectively analyzed, and immunohistochemistry (EnVision method) and molecular detection of glioma-associated oncogene homologue 1 (GLI1) gene translocation were performed. All cases were histologically reviewed with immunohistochemical staining for smooth muscle actin (SMA), CD10, CD117, DOG1, CD34, ER, PR, ALK and S-100. Fluorescence in situ hybridization (FISH) was used to detect the GLI1 gene translocation, and mutation of CKIT exons 9, 11, 13 and 17; and PDGFRA exons 12, 14 and 18 were identified by Sanger sequencing in four cases. Relevant literature was reviewed. Results: The study included four men and four women, age ranged from 26 to 72 years (mean 51 years). Histologically, the tumors were rich in small thin-walled blood vessels and myxoid matrix, and exhibited multiple nodular growth pattern in the gastric wall. The tumor cells were bland, spindled or oval. Immunohistochemically, all cases strongly expressed vimentin and SMA, and some expressed CD10 (4/8), desmin (3/8), H-caldesmon (5/8) and PR (5/8), but were negative for CD34, S-100, ER, ALK, CD117 and DOG1. The GLI1 gene translocation detection was performed in eight cases by FISH with three positive cases and five negative cases. Mutation analyses for exons 9, 11, 13, and 17 of CKIT genes and exons 12, 14, and 18 of the PDGFRA genes were performed and the tumors all of four tested cases were wild-type. Seven patients were followed up (ranged from 24 to 95 months, mean 50 months) after diagnosis and none of the patients had recurrence or metastasis. Conclusions: PF is a rare novel mesenchymal tumor of the stomach. Its distinct clinicopathologic features and immunohistochemical positivity for SMA, CD10 and PR can help differentiating this entity from other gastrointestinal mesenchymal tumors. FISH detection of GLI1 gene translocation offers an additional molecular diagnostic marker for the diagnosis.

Epigenetics: an alternative pathway in GISTs tumorigenesis.

Many diseases have different pathological backgrounds responsible for abnormal cell behavior and exhibiting altered function and signal transduction. This is especially true for tumors and although changes affecting DNA sequence, irreversible mutations and chromosomal aberrations in gastrointestinal stromal tumors (GISTs) have been widely studied, the importance of reversible epigenetic changes increasingly recognized in many cancers has received insufficient attention in these tumors. Epigenetic mechanisms are part of normal development and gene expression under normal conditions, but malfunction of these processes leads to malignant transformation by disturbing both intra- and intercellular communication. GISTs are a specific group of gastrointestinal tract tumors resistant to conventional chemotherapy and radiotherapy. Although they account for only 1% to 2% of tumors, they are among the most widespread gastrointestinal mesenchymal tumors. DNA hyper/hypomethylation overexpression/underexpression of miRNAs or abnormal histone modification may provide an alternative to the genetic modifications responsible for GIST pathology, response to treatment, prognosis and overall survival. This review summarizes the known epigenetic mechanisms involved in GIST pathogenesis; including onset, progression, and GISTs resistance. Reversible epigenetic changes are a novel and appropriate approach to halt the spread of metastases and the emergence of resistance in GIST treatment, and these changes depend on the type of epigenetic alternation, including inhibitors of histone acetyltranferase and deacetylase and DNA methyltransferases.

Management of esophageal gastrointestinal stromal tumor: review of one hundred seven patients.

Gastrointestinal stromal tumors (GIST) are the most common type of gastrointestinal mesenchymal tumor, but are rarely found in the thoracic esophagus. There is no clear consensus about the optimal treatment of this rare disease. A systematic search of the literature was performed for localized esophageal GIST that was resected between 2000 and 2015, and individual patients were included from two major academic institutions. We obtained information on demographics, tumor size and location, mitotic rate, treatment method, and time to recurrence or death. We performed univariate and multivariate Cox regression analyses to evaluate the factors associated with recurrence or death. A total of 28 studies met our inclusion and exclusion criteria, and with two patients from two academic institutions, we had a total of 107 patients in the study. Due to lack of uniformity among studies, there were several missing data for different variables. The average patient age was 56 (n =98) with mostly males (60%, n =91). The average tumor size on the CT scan was 7.9±5.4 cm (n =91), located mostly in the distal esophagus (81%, n =74). A similar number of patients underwent enucleation (n =47) compared to esophagectomy (n =42). Approximately half of the patients had a mitotic rate of 0-4 mitosis per 50 high-powered field (48%, n =80). The median survival time was 73 months with a 5-year disease free survival of 57% (n =97). Univariate Cox regression analyses showed that a large tumor, undergoing esophagectomy, and a high mitotic rate were associated with poor survival or recurrence control. We found that patients with a lesion smaller than or equal to 5 cm on the CT scan had a better disease-free survival rate than those with a size greater than 5 cm (HR =12.41, p =0.014) and had a 5-year survival rate of 92% with 90% of those patients undergoing enucleation (n =29). Esophageal GIST is a very rare malignancy. The tumor size and mitotic rate of the tumor are associated with poor survival. However, patients with esophageal GIST measuring 5 cm or smaller may be safely treated with esophageal enucleation.

LAPAROSCOPIC RESECTION OF GASTROINTESTINAL STROMAL TUMORS (GIST).

Background Gastrointestinal mesenchymal or stromal tumors (GIST) are lesions originated on digestive tract walls, which are treated by surgical resection. Several laparoscopic techniques, from gastrectomies to segmental resections, have been used successfully. Aim Describe a single center experience on laparoscopic GIST resection. Method Charts of 15 operated patients were retrospectively reviewed. Thirteen had gastric lesions, of which ten were sub epithelial, ranging from 2-8 cm; and three were pure exofitic growing lesions. The remaining two patients had small bowel lesions. Surgical laparoscopic treatment consisted of two distal gastrectomies, 11 wedge gastric resections and two segmental enterectomies. Mechanical suture was used in the majority of patients except on six, which underwent resection and closure using manual absorbable sutures. There were no conversions to open technique. Results Mean operative time was 1h 29 min±92 (40-420 min). Average lenght of hospital stay was three days (2-6 days). There were no leaks, postoperative bleeding or need for reintervention. Mean postoperative follow-up was 38±17 months (6-60 months). Three patients underwent adjuvant Imatinib treatment, one for recurrence five months postoperatively and two for tumors with moderate risk for recurrence . Conclusion Laparoscopic GIST resection, not only for small lesions but also for tumors above 5 cm, is safe and acceptable technique.

Schwannoma of the colon: A case report and review of the literature.

Colonic schwannomas are rare gastrointestinal mesenchymal tumors, and only a limited number of cases has been reported. The occurrence of these tumors is less common in the large intestine than in the stomach. The present study reports a case of colonic schwannoma in a 62-year-old female patient with no specific symptoms. The patient was diagnosed with a mass in the ascending colon by colonoscopy and abdominal computed tomography scanning. A right hemicolectomy was performed. The postoperative pathological diagnosis was ascending schwannoma. This case is noteworthy as colonic schwannomas are rare and are typically treated as colon cancer. No recurrence of the lesion was observed after 24 months of follow-up.

Role of PET/CT in Gastrointestinal Stromal Tumors

The first accurate description of mesenchymal neoplasms of the gastrointestinal tract (GIT) was in 1941. With the advent of immuno-histochemical analysis a definition of a new entity among gastrointestinal mesenchymal tumors called the gastrointestinal stromal tumors (GISTs); which particularly express the kit (CD117) protein; a growth factor trans-membrane receptor with tyrosine kinase activity(1 ) . Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal tumors of the gastrointestinal tract(2). GISTs are usually found in the stomach or small intestine but can occur anywhere along the gastrointestinal tract and rarely have extra-gastrointestinal involvement. Approximately 50-70% of GISTs originate in the stomach. The small intestine is the second most common location, with 20-30% of GISTs arising from the jejuno-ileum. Less frequent sites of occurrence include the colon and rectum (5-15%) and esophagus (<5%). Primary pancreatic, omental, or mesenteric GISTs have been reported but are very rare (3). Surgery remains the mainstay of therapy for patients with primary GIST who do not have evidence of metastasis and should be the initial therapy if the tumor is technically resectable with acceptable risk of morbidity. Regarding patients with a positive microscopic margin on final pathologic analysis, the management is still not well defined. There is no evidence that those patients with complete resection of all macroscopic disease, but still have microscopically positive margins, need to undergo re-excision. Lymphadenectomy is usually unnecessary because lymph node metastases are rare with GIST and sarcomas in general (4). There are different schemes for classification of GISTs on the basis of tumor size and mitotic count into very low risk, low risk, intermediate risk, and high risk. Alternatively, they are classified

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.

Application of gene mutation detection in gastrointestinal stromal tumors

Gastrointestinal stromal tumors(GISTs) are the most common gastrointestinal mesenchymal tumors of the gastrointestinal tract. Most of GISTs are characterized by mutation in the c-kit or PDGFR-α genes. In recent years, detection of gene mutation in GISTs has been widely used. In addition to the contribution to the diagnosis of difficult cases, such detection also has important value in predicting the efficacy of therapeutic drugs targeting, guiding clinical treatment and evaluating the prognosis of patients. In a word, gene mutation detection should be considered as the important standard for exact diagnosis and treatment of GISTs.

Gastrointestinal stromal tumor: recent advances in pathology and genetics.

The discovery of KIT gene mutation in gastrointestinal stromal tumor (GIST) has provided a paradigm shift in the classification, diagnosis and molecular-targeted therapy of gastrointestinal mesenchymal tumors. There is growing evidence of phenotype-genotype (KIT, platelet-derived growth factor receptor-alpha, succinate dehydrogenase or other driver gene mutation) and genotype-therapeutic (sensitivity to imatinib) correlations in GIST. Risk stratification based on mitotic counts, tumor size and rupture is useful for the prognostication and management of patients with GIST. Blood vessel invasion is a strong indicator of liver metastasis in GIST. In addition, novel biomarkers such as cell-cycle regulators, microRNAs and their targets have been discovered by using high throughput molecular analyses. In contrast, leiomyosarcoma of the gastrointestinal tract has become a very rare entity in the 'KIT' era, and its molecular pathogenetic mechanism is unclear. Recent studies have revealed a wide spectrum of cytological atypia, mitotic counts and biological behavior of gastrointestinal smooth muscle tumors, suggesting the necessity of establishing the criteria for malignancy. Collectively, both classical histopathological procedures and modern molecular investigations are indispensable for the evolution of diagnosis and treatment of GIST and mimics.

CTHRC1 Acts as a Prognostic Factor and Promotes Invasiveness of Gastrointestinal Stromal Tumors by Activating Wnt/PCP-Rho Signaling

Gastrointestinal stromal tumors (GISTs) are the major gastrointestinal mesenchymal tumors with a variable malignancy ranging from a curable disorder to highly malignant sarcomas. Metastasis and recurrence are the main causes of death in GIST patients. To further explore the mechanism of metastasis and to more accurately estimate the recurrence risk of GISTs after surgery, the clinical significance and functional role of collagen triple helix repeat containing-1 (CTHRC1) in GIST were investigated. We found that CTHRC1 expression was gradually elevated as the risk grade of NIH classification increased, and was closely correlated with disease-free survival and overall survival in 412 GIST patients. In vitro experiments showed that recombinant CTHRC1 protein promoted the migration and invasion capacities of primary GIST cells. A luciferase reporter assay and pull down assay demonstrated that recombinant CTHRC1 protein activated noncanonical Wnt/PCP-Rho signaling but inhibited canonical Wnt signaling. The pro-motility effect of CTHRC1 on GIST cells was reversed by using a Wnt5a neutralizing antibody and inhibitors of Rac1 or ROCK. Taken together, these data indicate that CTHRC1 may serve as a new predictor of recurrence risk and prognosis in post-operative GIST patients and may play an important role in facilitating GIST progression. Furthermore, CTHRC1 promotes GIST cell migration and invasion by activating Wnt/PCP-Rho signaling, suggesting that the CTHRC1-Wnt/PCP-Rho axis may be a new therapeutic target for interventions against GIST invasion and metastasis.

Tumor sites and microscopic indicators are independent prognosis predictors of gastrointestinal stromal tumors.

Gastrointestinal stromal tumors (GISTs) are the most common among gastrointestinal mesenchymal tumors, but its prognosis has not been accurately predicted by the current risk stratification guidelines, National Institutes of Health classification. In this study, we evaluated the predictive factors for GIST prognosis in a retrospective analysis of 332 patients. The data collected included tumor sites, including the esophagus, stomach, duodenum, small intestine, and extragastrointestinal sites; tumor size; microscopic indicators for malignant tumor behavior, such as the number of dividing cells, cell necrosis, atypical morphology, and invasion into the muscular or mucous layer; and previously established immunohistochemical indicators, CD117, CD34, and discovered on GIST-1 (DOG-1). No single occurrence of any microscopic indicators correlated with the prognosis of GIST; however, the total number of microscopic indicators was a significant prognostic factor of GIST (P < 0.001). Regarding the tumor sites, the order of prognostic risk (from the lowest to the highest) was as follows: the esophagus, stomach, duodenum, small intestine, extragastrointestinal sites, and colorectum. The association between tumor sites and prognosis was significant (P < 0.001). On the other hand, the expression of CD117 or CD34 was not associated with the risk of GIST. Importantly, 91% of the patients (302/332) showed the expression of DOG-1, and the lack of DOG-1 expression was associated with poor prognosis (P < 0.05). In conclusion, both tumor sites and total number of microscopic indicators are independent risk factors associated with the prognosis of GIST. The lack of DOG-1 expression may be predictive of malignant outcome.

Metastatic cerebellar gastrointestinal stromal tumor with obstructive hydrocephalus arising from the small intestine: a case report and review of the literature.

Gastrointestinal stromal tumor (GIST) is defined as a c-kit-positive gastrointestinal, mesenteric, or omental mesenchymal tumor that very rarely metastasizes to the brain. Metastasis to the cerebellum is particularly rare. An 80-year-old man presented with nausea and vomiting with disturbance of consciousness. Magnetic resonance imaging (MRI) revealed tumor in the cerebellar vermis causing obstructive hydrocephalus. The patient subsequently underwent midline suboccipital craniotomy, and the tumor was totally removed. Immunohistochemical analysis showed tumor cells positive for c-kit and CD34, and cerebellar metastasis of GIST was diagnosed. Postoperative radiotherapy was administered. Following surgery and radiotherapy, the patient developed ileus caused by tumor in the small intestine and underwent laparotomy for tumor removal. Following abdominal surgery, left hemiparesis and consciousness disturbance were noted. Computed tomography showed recurrent large tumor with perifocal edema in the right frontal lobe of the brain. The patient died 3 months after initial craniotomy. Intracranial metastasis of GIST is extremely rare. In cases such as the present, where the condition of the patient rapidly deteriorates and features such as rising intracranial pressure and ileus prevent the use of oral agents, molecular-targeted agents administered by intravenous infusion should be utilized.

A Rare Causing of Difficulty in Defecation: Rectal Schwannoma

Objective: Schwannomas are mainly benign, non-epithelial tumors originating in the Schwann cells, which form nerve sheaths. Schwannomas account for about 2-8% of all gastrointestinal mesenchymal tumors, encountered more frequently in the stomach and the small intestine. Schwannomas of the colon and rectum are extremely rare. Case Presentation: In this report, we present a thirty-nine-year-old woman admitted for complaints of rectal fullness and difficulty in defecation. At her rectal examination, a polypoid tumor 22x27x27mm in size was found filling the lumen of the rectum; it was well defined, with a homogeneous nature and benign appearance. Complete excision of the tumor was achieved by a transanal surgical approach. Histolopathological and immunohistochemical diagnosis of the tumor reported a rectal schwannoma. There has been no tumor recurrence at 18 months after surgical excision. Conclusion: A schwannoma of the rectum is rare; a benign tumor can usually be separated from GISTs with immunohistochemical staining, and it carries a good prognosis with local excision, which is the procedure of choice.

Endoscopic Ultrasound-Guided Fine Needle Biopsy without Rapid On-Site Cytologic Examination: A Time to Change the Paradigm?

Endoscopic Ultrasound-Guided Fine Needle Biopsy without Rapid On-Site Cytologic Examination: A Time to Change the Paradigm?

Insulin-like growth factor II messenger RNA–binding protein 3 expression in gastrointestinal mesenchymal tumors

Insulin-like growth factor II messenger RNA-binding protein 3 (IMP3) is a recently identified biomarker demonstrated to be useful in diagnosis and prognostic prediction for several kinds of malignant tumors. However, the clinicopathologic and diagnostic value of IMP3 in mesenchymal tumors of the gastrointestinal tract is not clear. In this study, we examined the immunohistochemical expression of IMP3 in gastrointestinal stromal tumor (GIST) (n = 150), malignant melanoma (n = 17), malignant mesothelioma (n = 6), leiomyosarcoma (n = 6), inflammatory myofibroblastic tumor (IMT) (n = 12), desmoid fibromatosis (n = 8), leiomyoma (n = 20), and schwannoma (n = 20). Focal (≥10%) or diffuse (≥50%) expression with strong staining for IMP3 was judged as positive. We found that malignant melanomas (16/17 cases, 94.1%), malignant mesotheliomas (5/6 cases, 83.3%), IMTs (7/12 cases, 58.3%), and leiomyosarcomas (2/6 cases, 33.3%) were positive for IMP3. Among IMTs and leiomyosarcomas, IMP3-positive cases were histologically and/or clinically aggressive subtypes. Other kinds of tumors, including GIST, desmoid fibromatosis, leiomyoma and schwannoma, were essentially negative for IMP3. Our results suggest that IMP3 may be an ancillary tool in identifying aggressive abdominal mesenchymal tumors other than GIST.

A Case of Benign Schwannoma of the Ascending Colon Treated With Laparoscopic-Assisted Wedge Resection

Isolated colonic schwannomas are rare gastrointestinal mesenchymal tumors. Only a small number of cases have been reported. Occurrence of these tumors is more common in the stomach than in the large intestine. These spindle cell lesions are distinct from leiomyoma, leiomyosarcoma, and gastrointestinal stromal tumors because the tumor cells have a distinct immunophenotype, with strong diffuse positivity for S-100 and vimentin, as well as corroborative negative staining of CD117 and smooth muscle markers. We present a case of colonic schwannoma in a 70-year-old woman who had no specific symptoms. The patient was diagnosed with a submucosal tumor in the ascending colon on colonoscopy and abdominal computed tomography. Laparoscopic-assisted wedge resection of colon was performed. The very rare pathologic diagnosis of ascending schwannoma was made postoperatively. This case is interesting because schwannomas of the colon and rectum are extremely rare and are treated by laparoscopic-assisted wedge resection.

Endoscopic Submucosal Dissection for Gastrointestinal Mesenchymal Tumors Adjacent to the Esophagogastric Junction: We Need to Do More

Extensive surgery is the mainstay of therapy for patients with gastrointestinal mesenchymal tumors (GIMTs) adjacent to the esophagogastric junction (EGJ). However, this modality is invasive and may interfere with anatomic consistency of the digestive tract. Therefore, we evaluated the feasibility, safety, and efficacy of endoscopic submucosal dissection (ESD) for GIMTs close to the EGJ and factors related to incomplete resection. For 39 GIMTs adjacent to the EGJ in 39 consecutive patients, the baseline information, complications, and therapeutic outcomes were recorded. Subsequently, risk factors, focusing on age, sex, tumor size, extent, shape, perforation presence/absence, and histopathology, were analyzed. Complete removal of junctional GIMTs was achieved in 32 cases, giving an overall complete resection rate of 82%. The mean tumor size was 16.1±12.7 (median, 12; range, 4-50) mm. There were no major intra- and postoperative complications, but two small perforations were found. The final histopathologic diagnoses included 28 leiomyomas, 10 gastrointestinal stromal tumors, and 1 schwannoma. No local recurrence or distant metastasis was observed during a mean follow-up of 15.7±8.4 (median, 16; range, 6-35) months. Univariate analysis showed incomplete resection was associated with tumor shape and size. Multivariate regression analysis identified tumor irregularity (odds ratio=37.50, 95% confidence interval=4.253-330.627) as the single factor associated with incomplete resection. ESD is feasible and safe for well-selected patients with GIMTs adjacent to the EGJ. Irregular tumor shape should be considered as a technical difficulty while performing ESD. Oncologic outcomes need to be assessed with longer follow-up.

Su1552 EUS-Based Identification of Predictive Factors for the Enlargement of Smts Measuring Less Than 20 mm

Gastrointestinal mesenchymal tumors (GIMTs), including GI stromal tumors (GISTs), are the most common type of submucosal tumors (SMTs) in the stomach. The Japanese GIST management guidelines recommend that small gastric SMTs measuring <20 mm be followed-up once or twice a year. However, the guidelines provide no protocol for the follow-up of such tumors. We have often encountered cases wherein endoscopic ultrasonography (EUS) analysis showed that the size of the GIMTs did not change during the follow-up period from initial diagnosis; however, we have also noted rare cases wherein gastric SMTs enlarged for a brief period. The possibility of malignancy is reported to increase with the size of the SMT. However, we cannot predict whether these tumors will enlarge in the future.[Aim] The aim of this study was to identify, using EUS, factors that can predict enlargement of GIMTs measuring <20 mm.[Patients] Endoscopic examination identified 978 patients with gastric GIMT between May 2007 and July 2012. Among these patients, 192 underwent EUS; we evaluated 70 patients who underwent EUS twice or more.