Extragastrointestinal Stromal Tumors Research Articles

Rare Double Primary Malignancies: A Pancreatic Gastrointestinal Stromal Tumor Mimicking as a Metastatic Lesion of Myoepithelial Carcinoma of Parotid Gland

Pancreatic gastrointestinal stromal tumors (PGISTs) are exceptionally rare, accounting for <5% of extra-gastrointestinal stromal tumors (EGISTs) and <1% of malignant pancreatic neoplasms. We present a unique case of concurrent double primary malignancies in a 46-year-old female with a history of recurrent myoepithelial carcinoma of the parotid gland, managed through surgical resection and adjuvant therapy. She presented with an enlarging abdominal mass, initially suggestive of pancreatic metastasis. Immunohistochemical analysis revealed positive staining for smooth-muscle actin (SMA) and CD34 in both parotid and pancreatic tissues. Importantly, CD117 expression was confined to the pancreatic tissue, confirming the diagnosis of PGIST rather than metastasis. Subsequently, a splenic-sparing distal pancreatectomy was performed, followed by immediate imatinib therapy. This case underscores the potential for the coexistence of rare primary malignancies with unique histopathological characteristics and organ involvement. When encountering a newly developed lesion in a distant organ, surgeons must consider the possibility of metastasis to guide therapeutic decision-making. Early diagnosis and appropriate intervention are paramount, particularly in the case of PGIST, given its infrequent presentation and clinical complexities.

Extra Gastrointestinal Stromal Tumour (EGIST) of Chest Wall Detected on 18F-FDG PET/CT: A Case Report and Brief Review of Literature

Gastrointestinal stromal tumors (GIST) are rare tumors accounting for less than 1% of primary neoplasia of the digestive tract. They can also occur outside the GIT, where they are called extra gastrointestinal stromal tumors (EGIST), which are extremely rare tumors. GISTS and EGISTS have similar histo-pathological and molecular profiles. Though these are known to be FDG avid, some of the atypical GISTS can be FDG negative or only minimally FDG avid. Here, an unusual case of a 57-year-old female with FDG avid solitary chest wall mass is presented, which after biopsy and immune-histochemistry was proven as EGIST. She underwent en block resection of the tumor and is presently on adjuvant treatment with Imatinib mesylate. This case report highlights the importance of considering EGIST as a differential diagnosis of a solitary chest wall mass and the utility of 18FFDG PET/CT in its management.

Survival analysis of extragastrointestinal stromal tumors based on the SEER database: a population-based study.

Extragastrointestinal stromal tumors (EGISTs) are rare mesenchymal neoplasms that originate outside the gastrointestinal tract. However, the population-level survival analysis of EGIST remains poorly grasped. Therefore, we aimed to analyze the survival of EGIST patients using the Surveillance, Epidemiology, and End Results (SEER) database. All patients diagnosed with GIST and EGIST between 2000 and 2019 were identified through utilization of the SEER database. Missing data were handled using multiple imputation methodology. Kaplan-Meier analyses and Cox proportional hazard models were employed to assess the influence of demographic and clinical characteristics on both overall survival (OS) and cancer-specific survival (CSS). A total of 13,330 patients were enrolled in the study, comprising 12,627 diagnosed with GIST and 703 with EGIST. EGIST patients demonstrated significantly poorer OS [hazard ratio (HR) 1.732, 95% confidence interval (CI) 1.522-1.970, P < 0.001] and CSS (HR 2.167, 95% CI 1.821-2.577, P < 0.001) compared to GIST patients. The mean 1-year, 3-year, 5-year, and 10-year OS rates for EGIST patients were 78.3%, 61.9%, 50.5%, and 32.5%, respectively, with corresponding mean CSS rates of 84.3%, 70.8%, 61.3%, and 46.5%. Multivariate Cox regression analysis identified age, race, sex, grade, size, and surgical type as independent risk factors for OS in EGIST patients, while age, sex, year of diagnosis, grade, surgical type, and radiation therapy were identified as independent risk factors for CSS. Patients with EGIST who underwent surgical treatment exhibited significantly higher 5-year OS rates (49.0% vs. 39.9%, P = 0.035) and CSS rates (63.9% vs. 53.0%, P = 0.028) compared to those who did not undergo surgery. EGIST patients have a poorer prognosis compared to GIST patients; however, surgical treatment has been shown to improve the prognosis.

Gastrointestinal Stromal Tumors: Our Ten-Year Experience of a Single-Center Tertiary Hospital.

Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal neoplasms of the gastrointestinal tract. They have variable clinical presentation, prognosis, and molecular characteristics. Here, we present the results of our retrospective study including patients operated on for GIST during the last decade. All the patients who underwent GIST resection during the decade 2008-2018 were included in the study. The diagnosis was based on the pathology report. All the data were collected and analyzed statistically using the Statistical Package for Social Science v25.0. Finally, after having applied the proper search terms, a comprehensive review of articles published in the Medline database was held. Thirty-two patients (sixteen women) were included in the study with a mean age of 69.6 years old (SD = 13.9). Twenty-one patients had a GIST in the stomach, eight in the small intestine, and three had an extra GIST. Of the 29 patients contacted, 21 were alive with a mean survival time of 74.3 months (SD = 49.6 months, min: 3.0 months, max: 161.0 months), whereas eight patients passed away. Finally, 13 patients were treated with tyrosine kinase inhibitors (TKIs) of whom only one died, while 9 patients passed away from those treated with surgery alone (p = 0.031). Our results were in concordance with the existing data in the literature. GISTs require patient-based therapeutical management depending on the histology of the tumors. Gastric tumors present a better prognosis than those localized in the intestine, while the use of TKIs has led to an improvement in patient survival rate.

Primary extragastrointestinal stromal tumor of the prostate: review of the literature and case report.

A 58-year-old man was presented with lower urinary tract symptoms for 6 months. A digital rectal examination revealed a markedly enlarged prostate with a smooth, bulging surface. Prostate-specific antigen density was 0.5ng/ml. MRI of the prostate showed an enlarged prostatic mass with hemorrhagic necrosis. Transrectal ultrasound-guided prostate biopsy was performed and pathological reports suggested a gastrointestinal stromal tumor. The patient refused radical prostatectomy and received only imatinib treatment. The diagnosis of EGIST of the prostate is extremely rare and depends on the histopathologic features with immunohistochemical results. The treatment is essentially based on radical prostatectomy, but there are other therapeutic modalities associating surgery with adjuvant or neoadjuvant chemotherapy. For patients refusing surgery, treatment with imatinib alone appears to be a therapeutic solution. Despite the rarity, EGIST of the prostate should be included in the differential diagnosis of patients presenting with lower urinary tract symptoms. There is no consensus regarding the treatment of EGIST, and the patients are treated as per the risk stratification.

Extra-gastrointestinal stromal tumors (EGISTs): A case report for a mischief entity.

Extra-gastrointestinal stromal tumor is a rare subtype of soft tissue sarcomas with significantly variable presentation, management, and prognosis. This makes it crucial to report the different institutional experiences of encountering extra-gastrointestinal stromal tumors (EGIST). We report 3 cases of EGIST diagnosis at American University of Beirut Medical Center for 2 males and 1 female in the 5th, 6th, and 7th decades of life, respectively. For the first case, the tumor was initially suspected to be ovarian cancer, but biopsy revealed a diagnosis of EGIST, and the patient was started on neoadjuvant therapy. In the second case, the tumor was retro-gastric and prelim diagnosis was gastric cancer but again biopsy revealed an EGIST histopathology, and the patient underwent surgery and adjuvant treatment. For the third case, a previous history of testicular cancer prompted an initial suspicion of recurrence with metastasis but biopsy and immunohistochemistry staining revealed EGIST with related markers. The patient underwent treatment at a different institution in his home country. This report sheds light on the importance of keeping EGIST amongst any differential list for abdominal and pelvic tumors. It also shows that EGIST-focused studies are needed to assess the effectiveness of the different treatment modalities available when utilized specifically for EGIST. This would allow for better oncological outcomes and improved quality of life.

Primary extra-gastrointestinal stromal tumor of retroperitoneum: Clinicopathologic characteristics and prognosis of six cases.

This study investigates the clinicopathological features and prognostic genic biomarker factors of primary retroperitoneal extra-gastrointestinal stromal tumors (EGISTs). The clinicopathological data of six patients with primary retroperitoneal EGIST were analyzed, including cell type (epithelioid or spindle), mitoses, and the presence of intratumoral necrosis and hemorrhage. Mitoses were counted and summed from 50 high power fields (HPFs). Mutations of exons 9, 10, 11, 13, 14, and 17 of the C-kit genes and those of exons 12 and 18 of the PDGFRA gene were examined. Follow-up was performed via telephone, and all outpatient records were reviewed. The last follow-up date was February 2022, the median follow-up was 27.5m and the postoperative status, medication, and survival of the patients were recorded. The patients were treated with radical intent. Four cases (patients 3, 4, 5, and 6) underwent multivisceral resection for encroachment on the adjacent viscera. The postoperative pathological results demonstrated that all biopsy specimens were negative for S-100 and desmin, and positive for DOG1 and CD117. Additionally, four patients (case 1, 2, 4, and 5) were positive for CD34, four (case 1, 3, 5, and 6) were positive for SMA, four (case 1, 4, 5, and 6) had >5/50 HPFs, and three (case 1, 4, and 5) had Ki67 >5%. According to the modified National Institutes of Health (NIH) guidelines, all patients were graded as high-risk cases. By exome sequencing, exon11 mutations were detected in the six patients, while exon10 mutations were detected in two cases (patients 4 and 5). The median follow-up time was 30.5 (11-109) months, with only one fatality at 11 months. Retroperitoneal EGIST is a rare mesenchymal tumor that is difficult to distinguish from other retroperitoneal tumors. To diagnose this highly malignant tumor, low-threshold suspicion is necessary, and Kit and PDGFRA gene mutations should be routinely tested to confirm the diagnosis and guide subsequent treatment.

Primary Extra-Gastrointestinal Stromal Tumors (E-GIST) of the Liver, about Two Cases and Review of the Literature Oncology Hospital Experience at Chu Hassan II in FES

Introduction: Primary extra-gastrointestinal stromal tumors (E-GIST) of the liver are rare. The clinical presentation can range from asymptomatic to bleeding or manifestations of mass effect. Cancer surgery followed by adjuvant treatment with imatinib is the standard of care. However, in special circumstances, a cytoreductive approach may represent a therapeutic option. We describe here the case of two patients who presented with a painful and protruding epigastric mass, the first case was a localized E-GIST candidate for neoadjuvant treatment with imatinib with complete resection surgery thereafter with very good evolution, and the second is that of an E-GIST of the liver at an advanced stage with an evolution very quick to death. Conclusion: Primary liver E-GIST is a rare condition. Treatment is based on systemic therapy and total resection surgery. However, cytoreductive surgery will be required when complete resection is not possible.

Epithelioid extragastrointestinal stromal tumor in the pelvic cavity: A rare case at a rare location

Epithelioid extragastrointestinal stromal tumor in the pelvic cavity: A rare case at a rare location

A Rare Case of Gastrointestinal Stromal Tumor of the Abdominal Wall

Gastrointestinal stromal tumors (GIST) are rarely encountered in medical practice, developing with predilection in people over 40 years old. Their starting point is found in the digestive tract, and can appear anywhere along it. Normally, in the human body cells go through the processes of development, division and then apoptosis. In the case of gastro-intestinal stromal tumors, the cells divide continuously and the process of apoptosis is no longer carried out, forming these tumors, which can be benign or malignant. The essential medical treatment used in the case of gastrointestinal stromal tumors is Imatinib, which has the role of preventing the growth or even regression in size of the tumor in most cases. The specificity marker for GIST is represented by c-KIT protein, and immunohistochemically, the majority of gastrointestinal stromal tumors show positivity for CD34 and c-KIT. There are also extragastro-intestinal stromal tumors, for example located in the liver, duodenum, pancreas, but they are extremely rare, being considered rather as metastases from the primary tumor.

An Extragastrointestinal Tumor Diagnosed as a Vaginal Mass during Pregnancy

We report a case of an extragastrointestinal stromal tumor diagnosed as a vaginal mass during pregnancy. The mass was detected during routine examination at 24 weeks of gestation. At 26 weeks, the patient underwent transvaginal ultrasonography and magnetic resonance imaging, which revealed a blood flow-rich mass of approximately 50 × 30 mm in the rectovaginal septum. At 29 weeks of gestation, we resected the mass vaginally and the pathological diagnosis was a gastrointestinal stromal tumor. Chemotherapy was withheld until after full-term birth because the proliferation index of the tumor cells was low. The patient delivered a healthy infant. Imatinib was commenced at 1 month postpartum, with no recurrence or metastasis after 2.5 years. An extragastrointestinal stromal tumor as a vaginal mass in pregnancy has not been reported; however, our case suggests that the tumor should be considered a differential diagnosis of a vaginal mass in pregnancy.

S2210 A Rare Retroperitoneal Mass Simulating a Complicated Diverticulitis

Introduction: Extra-gastrointestinal stromal tumors (EGISTs) are a group of rare neoplasm that arises from cells outside the gastrointestinal (GI) tract but with similar pathologic characteristics as of gastrointestinal stromal tumors (GISTs). They account for only 5% of all GISTs involving the retroperitoneum, mesentery or omentum. EGISTs typically presents as large intra-abdominal masses with unspecific symptoms and are known to have a more aggressive behavior than its GI counterpart. Case Description/Methods: A 50-year-old male inmate with no medical history presents to the ED after having unquantified episodes of non-bloody, non-watery diarrhea and vomiting of gastric content for 5 days prior to admission. The patient also reports subjective fever and constant left quadrant abdominal pain. Upon physical exam, he was found with signs of dehydration, a distended abdomen with hyperactive bowel sounds, and a non-mobile large mass on the left lower quadrant with tenderness to light palpation. Laboratories were remarkable for neutrophilic leukocytosis, thrombocytosis, and elevated inflammatory markers. Abdomino-pelvic CT revealed a large left heterogeneously enhancing retroperitoneal mass with central necrosis measuring 18.6 cm AP x 18.4 cm transverse x 25.3 cm CC causing mass effect over the left kidney with loss of intervening fat planes, flattening of the left adrenal gland and displacement of the stomach, small and large bowel with almost complete collapse of the distal transverse and descending colon. Core-needle biopsy revealed high-risk GIST with positive immunohistochemistry for C-KIT, CD34, CD56, actin, and desmin with a very high mitotic index (45 mitosis/25 HPF). Surgery was deferred due to large size of mass and closure to adjacent structures. Neoadjuvant therapy with Imatinib was started but patient was lost to follow up upon discharge. Discussion: This case describes a rare presentation of EGIST emerging from the retroperitoneum with a positive immunohistochemistry for desmin and manifesting as a complicated diverticulitis. Although there is limited data about its origin, EGISTs and GISTs are recognized to be molecularly identical. Furthermore, because EGISTs are found outside the GI system, symptoms only appear when the tumor has progressed to an advanced stage giving it a worse prognosis. As a result, having EGIST as a differential diagnosis for abdominal mass is crucial. More research is needed to better understand the behavior, prognosis, and treatment options of these tumors.

Mesenteric lymphoma - a case report

Gastrointestinal stromal tumors (GISTs) comprise a group of smooth muscle mensenchymal alimentary tract tumors of variablemalignancy (1) GISTs may ouccur anywhere along the gastrointestinal tract, they are most commont located in the stomach (50-60%) and the small intestine (30-35%), and less frequenty in the colon, rectum and esophagus (2). More rarely, GISTs may arisefrom other intra-abdoment soft tissues within the abdominal cavity, usually in the omentum, mesentery or the retroperitoneumcalled extra-Gastrointestinal stromal tumors (EGIST). Three macroscopic growth patterns of GIST: intraluminal, exophytic(extraluminal), and transmural tumors with the distribution was even (3).In this study, we describe case report of 70-year-old man was admitted to our hospital because of abdominal pain over 6months with no pathological antecedent. Abdominal ultrasound (US) reveal a omental solid mass in left lumbar region, andon CT scan show a solid mass in left lumbar region in front of the descending colon, maesuring around 50x87x133mm withwell-circumscribed, slight enhance with intravenous contrast, no hemmorrage or necrosis area, no calcification and not clearlyseparated from small-bowel. Patient has laparoscopic surgeon, diagnosis was a pedunculated exoluminal gastrointestinal stromal tumor (GIST). Histopathological examination report and the CD-117 immunoreactive score is suitable of endoscopicallyinvisible medium sized.

Morphological and immunohistochemical diagnostic of extragastrointestinal stromal tumors - a 51 case series analysis.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the digestive tract, originating from structures differentiating towards Cajal cells. Due to their morphology and localization, the extragastrointestinal stromal tumors (EGISTs) can be a diagnostic challenge. We investigated a series of 51 EGISTs diagnosed in our institutions, aiming to explore the immunophenotypes and to analyze the process and the utility of the antibodies required for a positive diagnosis. Immunohistochemical examinations were done for pan-cytokeratin (pan-CK), Ki67, discovered on GIST1 (DOG1) protein and platelet-derived growth factor receptor alpha (PDGFRA), as necessary. The main tumor site was abdominal wall in 43 (84%) cases, most of the tumors showed spindle cell cellularity, followed by mixed and epithelioid type. Twenty-six cases revealed a full conventional immunohistochemical profile with DOG1 positivity. In 10 cases, c-KIT expression was absent but with the preservation of cluster of differentiation (CD)34 positivity, and eight cases were positive for PDGFRA. In our study, we found a subgroup of eight cases presenting in extra-abdominal settings (including one in lung and two in the head-and-neck area). We concluded EGISTs represent a histopathological and immunohistochemically challenging subgroup testing more often negative for c-KIT mutations and positive for PDGFRA compared to GIST. DOG1 remains the marker of choice regardless of tumor site, while CD34 and CD117 should be considered as adjuvants.

Pancreatic Extra-Gastrointestinal Stromal Tumour Presenting as an Intra-Abdominal Abscess: A Case Report and Literature Review

Introduction: Pancreaticoduodenectomy is one of the most frequently performed operations for pancreatic lesions around the world. Some pancreatic malignancies are particularly rare and difficult to diagnose preoperatively. Gastrointestinal stromal tumour is a common mesenchymal neoplasm of the gastrointestinal tract rarely found outside its boundaries. We report a case of a patient who presented to our hospital with a large intra-abdominal abscess with a unique post operative pancreatic extra-gastrointestinal stromal tumour (EGIST) as the final pathology. Presentation of case: We report a -32 year- old female who was admitted through the emergency department complaining of epigastric pain of one-week duration associated with spikes of fever and anorexia. The performed investigations manifest a large mass with infected central necrosis. The patient was managed initially with percutaneous drainage and intravenous antibiotics. Two weeks later the patient underwent whipple’s procedure and was discharged home uneventfully. The final histological report came as pancreatic extra-gastrointestinal stromal tumour. Discussion: Primary EGISTs outside the gastrointestinal tract are quite rare and account for up to 5%. It can originate from any mesenchymal organ. Primary pancreatic EGIST is a distinctly and extremely rare tumour. only few cases have been reported in the literature. Conclusion: Despite the rarity of this type of malignancy involving the pancreas, all hepatobiliary surgeons should keep it in mind as a possible pathology. Much effort must be done to make the diagnosis preoperatively apart from emergency presentation. Large pancreatic tumours with necrosis or cystic degeneration should ignite the suspicion of EGIST.Tabled 1Histology reportCD117+CD34+Desmin-Synaptophysin-Chromogranin-Lymph N14 reactive Open table in a new tab

Histomorphological Spectrum and Immunohistochemical Features of Gastrointestinal Stromal Tumour: A Series of Eight Cases

Gastrointestinal Stromal Tumours (GISTs) are rare tumours of the Gastrointestinal Tract (GIT), consisting of &lt;1% of all primary GIT neoplasms. Recent studies show an increased incidence, which may be due to improved diagnostic facilities. In contrast to the literature’s judgement and the findings of many Western research, which state that the stomach is the most common place, it was observed that the small intestine was more common. Consequently, the goal of this case series was to characterise the clinicopathological, histomorphological, and immunohistochemical spectrum of GISTs as well as their risk categorisation in accordance with the modified Miettinen and Lasota’s algorithm. Eight patients with GISTs diagnosed between January 2017 and December 2020 at tertiary care centre of Gujarat, India are presented in this case series. There was one young woman among the patients, others were middle or old age male or female and had a median age of 58.5 years. The most typical presentation was abdominal pain, albeit in one instance it was an unexpected discovery. One example of extra Extra GISTs (EGIST), where there were several retro and intraperitoneal masses, and one small intestinal GIST each had lymphoma as the tentative clinical diagnosis. Predominant spindle cell morphology was observed in contrast to other studies. Even if molecular studies are not available in resource-limited countries, the basic Immunohistochemistry (IHC) panel is the most useful in the final diagnosis. Risk stratification criteria are helpful for prognostication and further management with the use of appropriate targeted therapies.

Clinical Features of Extragastrointestinal Stromal Tumor Compared with Gastrointestinal Stromal Tumor: A Retrospective, Multicenter, Real-World Study.

Objective This study aimed to compare the tumor characteristics and long-term outcomes between EGIST and GIST. The confounding function was applied to improve the result credibility in the case of small sample size. Design, Setting, and Participants. This cohort study enrolled 55 patients with EGIST who underwent surgery and were selected from four high-volume hospitals in China and 221 GIST patients who were collected from one of the four hospitals between January 2006 and September 2017. We used propensity score matching (PSM) and subgroup analysis to compare EGIST with GIST in terms of prognosis. The confounding function was used for sensitivity analysis to reduce unmeasured confounding. Results We matched 43 patients in each of the GIST and EGIST groups by PSM. We compared EGIST data with GIST data to explore the prognostic factors between them. In the multivariate Cox regression model, tumor location of EGIST was negatively correlated with overall survival (after PSM: HR, 4.32; 95% CI, 1.22–15.26) or disease-free survival (after PSM: HR, 9.79; 95% CI, 2.22–43.31), which was also intuitively shown in the Kaplan–Meier survival curves (all P values < 0.05). In the subgroup analysis, EGIST with high risk factors had a worse prognosis than GIST. In unmeasured confounding analysis, the overall curve tends to show all combinations of c(0) of c(1) up to 2.0, none of which would bring the corrected relative risk to 1 for OS and DFS. Conclusions and Relevance. EGIST was associated with worse prognosis compared with GIST patients, particularly in EGIST patients with high risk factors, while there was a similar prognosis without those high risk factors.

Whole‑exome sequencing for high‑risk primary prostatic extra‑gastrointestinal stromal tumor: A case report

The low incidence rates of prostatic extra-gastrointestinal stromal tumors (EGIST), combined with the lack of published guidelines on its treatment, often results in its misdiagnosis and challenges in the treatment of patients, even in cases with high-risk factors. The present case study reported a 65-years-old Chinese male patient, who presented with intermittent hematuria and lower urinary tract symptoms for three months. The colonoscopy results revealed no gastrointestinal lesions; however, a core biopsy diagnosed an EGIST, which subsequently underwent radical prostatocystotomy, standard pelvic lymph node resection, and bricker ileal conduit diversion. The postoperative pathological results suggested a high-risk primary prostatic EGIST, according to the aggressive behavior of the GIST. The immunohistochemistry results revealed the positive expression of CD117, DOG1, CD34, androgen receptor AR, prostate-specific antigen (PSA), a 2% Ki-67 index and a positive surgical margin. The whole exome sequencing (WES) results revealed that the patient harbored a single nucleotide mutation in 121 genes and copy number variations in 601 genes, including a defect in c-Kit (in-frame deletion in p.Q556-V560; fold, 17.5%). By compiling the data obtained from the ConsensusPathDB and the drug-gene interaction databases and expert opinions, the patient was prescribed with the personalized drugs (400 mg per day imatinib mesylate and 50 mg per day bicalutamide, which were stopped when the PSA levels remained stable below 0.01 ng/ml) for 18 months follow-up and there were no signs of recurrence. In conclusion, WES identified multiple genomic alterations and the underlying genetic defect in the rare case enabled the evaluation of the prognosis and the decision of potential drug candidates. The underlying mechanism of the substantial genetic variations in the primary prostatic EGIST, as well as the malignant behaviors of the tumor, remain to be investigated.

S3071 Humongous Refractory Gastrointestinal Stromal Tumor With an Unusual Mutation

Introduction: Gastrointestinal stromal tumors (GIST) are rare mesenchymal neoplasms that arise from any part of the gastrointestinal tract. Its incidence varies between 7 and 8 percent per million inhabitants per year with a and median age of diagnosis of 63 years old. Extragastrointestinal stromal tumors make up less than 5 percent of cases, and most cases are secondary to advanced disease. Here we present a case of a catastrophic progression GIST with few or no previously documented mutation refractory to available therapies. Case Description/Methods: A 46-year-old man with a history of Omental GIST in remission after 5 years of treatment after imatinib attended the emergency room due to abdominal pain. Symptoms began suddenly with constipation, early satiety, and changes in stool size. Physical examination with a distended abdomen and positive liquid wave. laboratory analysis with 9.4 g / dL of hemoglobin. Abdominal CT reveals a large mesenteric mass measuring 15.6 x 10.2 x 24.6 cm in the lower abdomen extending into the pelvic region. Biopsy of the lesion reported a high-risk recurrent GIST with high Ki67 proliferation and a very high mitotic range. High-throughput and pathological sequences reported negative mutations in C-kit, CD117 and CD34, CDX-2, Betacatenin, LCA, CD3, CD20, Vimentin, and EXON 13,14 positive. Treatment was started with unanswered imatinib and then switched to sunitinib with disease progression and worsening disease burden. Treatment with regorafenib was started but, unfortunately, aggressive progression of the disease with a mass effect that affects multiple organs, so the patient did not tolerate the therapy. During the prolonged stay, the patient was complicated by spontaneous bacterial peritonitis, massive pulmonary embolism, and multi-organ failure, resulting in his death. Discussion: Our patient presented mutations in exon 13 and 14 rarely described in the literature that makes up less than 1% of GIST cases and does not have definitive treatment. It is presumed that the mutation in exon 13 responds to imatinib although in our patient it did not slow it down. progression of the disease. KIT-negative GISTs that progress during or after treatment with sunitinib and imatinib can be challenging for pathologists and clinicians. The implementation of next-generation gene sequences in clinical practice provides a major step forward in the implementation of target therapies and further studies. Tumor markers need to be developed for early detection, monitoring, and treatment.

P-93 The characteristics and prognosis of extragastrointestinal stromal tumors: A single center retrospective analysis of 31 patients

Extragastrointestinal stromal tumors (EGISTs) are a special type of gastrointestinal stromal tumors (GISTs) that have similar pathologic characteristics but without any connection to the alimentary tract. Although EGISTs have been reported seemingly with more malignant behaviors by previous publications, the understanding of EGISTs still remains to be improved for its extremely rare prevalence. The aim of this study was to investigate the basic features of EGISTs and analyze the factors related to prognosis.