[GI hemorrhage with fulminant shock induced by jejunal gastrointestinal stromal tumor (GIST) coincident with duodenal neuroendocrine carcinoma (NET) + neurofibromatosis (NF) -- case report and review of the literature]

Jejunal GIST masquerading as an ovarian mass: A case report

INTRODUCTION AND IMPORTANCE

Gastrointestinal stromal tumors (GIST) are rare mesenchymal tumors originating in the wall of the gastrointestinal tract. Jejunal GIST is the rarest subtype. Large GIST can present with an abdominopelvic mass which can be preoperatively misdiagnosed as a gynecological tumor.

CASE HISTORY

A 44-year regularly menstruating woman presented with lower abdominal pain which was diagnosed as a malignant ovarian tumor preoperatively with an MRI. However, intraoperatively, a lobulated mass was present in the abdominal cavity arising from a jejunal portion of the small intestine. With an intraoperative diagnosis of jejunal GIST, the mass was excised and jejunum anastomosed. Histopathology examination report showed GIST which was further confirmed by immunohistochemistry.

DISCUSSION

GIST presenting as a large abdominopelvic mass can mimic a gynecological tumor. Contrast-enhanced CT scan is the preferred imaging modality for the evaluation of patients with suspected GIST to determine the extent of the tumor, the presence or absence of metastatic disease alongside evaluation of the possibility of complete resection. Adjuvant imatinib therapy following complete excision can decrease the disease recurrence.

CONCLUSION

Gynecologists should keep in mind that primary gastrointestinal tumors can present as a pelvic mass. A proper histopathological examination helps to confirm the diagnosis. Complete surgical removal of the tumor should be obtained as it determines the prognosis of the disease.

Football Size Jejunal Gastrointestinal Stromal Tumour

Gastrointestinal stromal tumours (GISTs) are considered the most common mesenchymal neoplasms of the alimentary tract, yet they account for only 0.2% of all gastrointestinal neoplasms.

We are presenting a case of a 68-year-old gentleman who was diagnosed with a 250 mm jejunal GIST only when he presented with abdominal pain and fullness in the upper abdomen. We believe that detailed medical history, followed by prompt investigations, will help in early diagnosis of small GISTs with less malignant potential, which in turn will lead to better outcomes.

Therapeutic Potential of PI3K/AKT/mTOR Pathway in Gastrointestinal Stromal Tumors: Rationale and Progress

Simple Summary

Most gastrointestinal stromal tumors (GISTs) arise due to gain-of-function mutations of KIT and PDGFRA, encoding the receptor tyrosine kinase (RTK). The introduction of the RTK inhibitor imatinib has significantly improved the management of GISTs; however, drug resistance remains a challenge. Constitutive autophosphorylation of RTKs is associated with the activation of the PI3K/AKT/mTOR pathway. Especially, this pathway plays a pivotal role in mRNA translation initiation, directly regulated by eukaryotic initiation factors (eIFs). This review highlights the progress for targeting PI3K/AKT/mTOR-dependent mechanisms in GISTs and explores the relationship between mTOR downstream eIFs and the development of GISTs, which may be a promising future therapeutic target for this tumor entity.

Abstract

Gastrointestinal stromal tumor (GIST) originates from interstitial cells of Cajal (ICCs) in the myenteric plexus of the gastrointestinal tract. Most GISTs arise due to mutations of KIT and PDGFRA gene activation, encoding the receptor tyrosine kinase (RTK). The clinical use of the RTK inhibitor imatinib has significantly improved the management of GIST patients; however, imatinib resistance remains a challenge. The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is a critical survival pathway for cell proliferation, apoptosis, autophagy and translation in neoplasms. Constitutive autophosphorylation of RTKs has an impact on the activation of the PI3K/AKT/mTOR pathway. In several preclinical and early-stage clinical trials PI3K/AKT/mTOR signaling inhibition has been considered as a promising targeted therapy strategy for GISTs. Various inhibitory drugs targeting different parts of the PI3K/AKT/mTOR pathway are currently being investigated in phase Ι and phase ΙΙ clinical trials. This review highlights the progress for PI3K/AKT/mTOR-dependent mechanisms in GISTs, and explores the relationship between mTOR downstream signals, in particular, eukaryotic initiation factors (eIFs) and the development of GISTs, which may be instrumental for identifying novel therapeutic targets.

Primary Jejunal Gastrointestinal Stromal Tumor: Diagnosis Delay of 3 Years but Successful Management in Early Stage (II) by Surgery and Adjuvant Therapy

In the digestive system, mesenchymal origin of tumors is quite rare; in general, they are recognized as gastrointestinal stromal tumors (GISTs). The incidence of GISTs is very low (2 in 100,000), while jejunal GISTs are extremely rare, accounting for 0.1-3% of all gastrointestinal (GI) tumors. Small intestinal GISTs are the second most common (25%) site in the GI tract, usually occurring in the duodenum. We present the case of a 62-year-old Bangladeshi female with a history of GI bleeding 3 years earlier; the cause of the bleeding had not been found despite extensive investigations. In the meantime, the patient had developed occasional abdominal pain and lumpy feelings in the right side of the abdomen without any GI bleeding. Exploratory laparotomy was carried out in view of a small intestinal mesenteric mass in a computed tomography scan. On midline incision there was a 6 × 6 cm mass in the antimesenteric border of the jejunum approximately 30 cm from the duodenojejunal flexure, which was resected followed by anastomosis. The presentation of GISTs ranges from asymptomatic to mild abdominal pain and mass (5-50%) and mechanical obstruction (5%) as well as hemorrhage - perforation having rarely been reported (0.8%) - making the diagnosis difficult. Exophytic growth of these tumors has been noted in 18-30% of cases. In view of intermediate risk of malignancy, the patient was started with adjuvant imatinib 400 mg once daily due to probability of disease recurrence (24%).

Duodenal somatostatinoma presenting as obstructive jaundice with the coexistence of a gastrointestinal stromal tumour in neurofibromatosis type 1: a case with review of the literature

Somatostatinomas are rare neuroendocrine tumours, mostly located in the pancreas or duodenum, with an estimated incidence of 1 in 40 million. Duodenal somatostatinomas (DSs) are usually found in association with neurofibromatosis type 1 (NF1), tuberous sclerosis and Von Hippel-Lindau syndrome. Gastrointestinal stromal tumours (GIST) have also been described in NF1, but the association with somatostatinoma is very uncommon. We report the case of a patient with NF1 who presented with obstructive jaundice due to multiple firm nodules around the ampulla of Vater. A pancreaticoduodenectomy was performed and revealed a 1 cm duodenal/ampullary mass which stained positive for somatostatin, together with a GIST also found on the duodenal wall. Despite its rarity, ampullary somatostatinomas should be considered in the differential diagnosis of biliary tract dilation in patients with NF1.

Small Intestinal and Mesenteric Multiple Gastrointestinal Stromal Tumors Causing Occult Bleeding

Gastrointestinal stromal tumors are the meseancymal neoplasms which may involve any part of gastrointestinal tract. C-Kit and platelet derived factor receptor alpha polypeptide are believed to be responsible for the genetic basis. This case presentation aimed to discuss the diagnostic and therapeutic modality of multiple small intestinal, omental, and mesenteric GISTs with different sizes which caused occult bleeding in a 43-year-old male patient.

The Coexistence of Somatostatinoma and Gastrointestinal Stromal Tumor in the Duodenum of a Patient with Von Recklinghausen's Disease

We herein describe a case of somatostatinoma coexisting with a gastrointestinal stromal tumor (GIST) in the duodenum of an 81-year-old woman with Von Recklinghausen's disease (VRD) and common bile duct stone who presented with diarrhea of three months in duration. Gastroduodenoscopy revealed an ulcer on the second part of the duodenum. A 2.1-cm enhancing tumor was observed to extend from the ulcer on an abdominal computed tomography scan. Subtotal stomach-preserving pancreaticoduodenectomy revealed a somatostatinoma on the papilla of the vater and duodenal GIST. There have been only eight reports on VRD associated with ampullary somatostatinoma and GIST. An awareness of this possibility in patients with gastrointestinal lesions is necessary for proper treatment and patient management.

Case Report: Jejunal gastrointestinal stromal tumour, a rare tumour, with a challenging diagnosis and a successful treatment

Gastrointestinal stromal tumours (GISTs) are rare. GISTs comprise 0.2% of gastrointestinal tumours and only 0.04% of small intestinal tumours. Jejunal GISTs are the rarest subtype. Only 10–30% progress to malignancy [Choi (Response evaluation of gastrointestinal stromal tumors. Oncologist 2008;13:4–7)]. We present a 70-year-old male, with multiple co-morbidities, who had extensive investigations over 5 years for vague abdominal pain. All investigations were normal. He presented with symptoms and signs of small bowel obstruction (SBO), confirmed on a computed tomography scan and demonstrated to be secondary to lesion-induced intussusception. The patient had emergency small bowel resection, was discharged after 4 days and remains well. This case report highlights the rarity of jejunal GISTs and, as extensive initial investigation yielded all false-negative results, indicates the difficulty in diagnosing jejunal GISTs. Adhesions are the commonest cause of SBO in patients with previous abdominal surgery, followed by newly diagnosed malignancies [Beardsley et al. (Small bowel obstruction in the virgin abdomen: the need for a mandatory laparotomy explored. Am J Surg 2014;208:243–8)]. Consequently, in patients with a virgin abdomen, underlying tumours should be considered.

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 (<2 cm). 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 (<2 cm) 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.

Intestinal obstruction in von Recklinghausen's disease

AIM

Gastrointestinal manifestations occur in up to 25% of patients with neurofibromatosis type 1. This review reports all published cases of acute intestinal obstruction due to neurofibromatosis type 1 and identifies mechanisms of obstruction, the nature of the tumour and the outcome.

METHOD

A systematic review of the literature on acute intestinal obstruction due to neurofibromatosis type 1 was performed by searching the major electronic databases. All relevant references were reviewed for possible inclusion. All the references of the relevant articles were screened for any further articles that were missed in the initial search.

RESULTS

We identified 25 articles from 1972 to 2013 reporting 25 patients with von Recklinghausen's disease who underwent laparotomy for acute intestinal obstruction. Three further patients were operated on in our institution. The mean age of the patients was 44.2 years and the male/female ratio 15/13. The mechanisms of obstruction were intrinsic obstruction (16), extrinsic obstruction (8) and intussusception (4). Histology was reported to show neurofibroma (19), gastrointestinal stromal tumour (5) and adenocarcinoma (4). Among patients whose outcome was mentioned (17), 10 were asymptomatic after a mean follow-up of 1.5 years.

CONCLUSION

Acute bowel obstruction is a rare manifestation of neurofibromatosis type 1. Surgery is often necessary to treat the complication and to determine the exact nature of the tumour and the prognosis.

Coexistence of gastrointestinal stromal tumours (GIST) and malignant neoplasms of different origin: prognostic implications

BACKGROUND

Over the past decade, several changes occurred in diagnostics, treatment and understanding of pathogenesis of gastrointestinal stromal tumours (GIST). However, their coexistence with other malignancies of different histogenetic origin remains a challenging issue.

METHODS

Patients diagnosed with GIST in a 10-years period were identified retrospectively and clinical history and findings thoroughly explored for the presence of associated other malignancies. Follow up data were obtained and analysed for prognostic impact of the concurrent malignancy and/or GIST.

RESULTS

Thirty seven (27 males, 10 females) of 86 GIST-patients (43%) had another malignancy. Mean age was 70 years. Associated malignancies were gastrointestinal (n = 29; 69%), renal-/urological (n = 5; 12%), haematological (n = 4; 9.5%), cutaneous (n = 3; 7%) and thyroid (n = 1; 2.5%) in origin. Majority of GISTs occurred in stomach (65%) and small intestine (30.6%) and most (78%) were asymptomatic incidental findings during diagnostic or therapeutic procedures for associated malignancies. GIST size ranged from 0.1 cm to 9 cm (mean, 2.2 cm) and all of them had a low (<5/50 HPFs) or no mitotic activity. Thirty-one tumours (84%) were of no/very low/low risk and 6 were of intermediate risk. During follow-up (range 3-160 months, mean; 60 months), one patient suffered from distant metastases of GIST. Seven patients (19%) died of associated malignancies and three patients (8%) of other non-tumour-associated cause, but none died of GIST.

CONCLUSION

Coexistence of GIST with other malignancies is higher than previously reported and should draw attention of clinicians towards these incidental findings. Prognosis in these patients is usually determined by other malignancy and not significantly influenced by GIST. Therefore treatment algorithms should be focused on prognostically relevant malignancy.

Gastric GIST with synchronous neuroendocrine tumour of the pancreas in a patient without neurofibromatosis type 1

The gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the gastrointestinal tract. These are rare tumours with an incidence of 15 new cases per million per year. The occurrence of neuroendocrine tumours of the pancreas is rare, representing 1-5% of pancreatic cancers, and it is estimated that its incidence does not exceed five to one million. GISTs are common in patients with neurofibromatosis type 1 (NF1); there are few reported cases of synchronous neuroendocrine tumours in these patients and most are pheochromocytomas. The case reports a 64-year-old woman referred to the General Surgery Outpatient for incidental finding of gastric and pancreatic tumours. She underwent a radical subtotal pancreatectomy + partial gastrectomy with jejunal transposition. The pathological examination revealed: gastric GISTs and a well-differentiated neuroendocrine carcinoma of the pancreas. This is the second case published so far of a patient with both tumours and without NF1. Posterior studies must be performed to evaluate if some other genetic disorder is involved in these patients without NF1.

The inside mystery of jejunal gastrointestinal stromal tumor: a rare case report and review of the literature

Gastrointestinal stromal tumors (GISTs) are malignant and rare form of soft tissue sarcoma of the digestive tract. The incidence of gastrointestinal stromal tumors is very low Kramer et al. 2005 Jejunal GISTs are extremely rare. Here we present a rare case of jejunal GIST with unusually large size at presentation. The patient presented with severe abdomen pain, exophytic growth, and dimorphic anemia. Surgical resection of the tumor was carried out, and operative findings revealed a 15 × 10 cm growth, arising from serosal surface of jejunum, at the antimesenteric surface. Diagnosis in this case was made by subjecting the resected specimen to immunohistochemical analysis. In view of large size of the resected tumor, and high-risk histopathological features, imatinib mesylate 400 mg once daily was given as adjuvant chemotherapy. Patient is asymptomatic without any evidence of tumor recurrence after six months of postoperative followup. Imatinib as such is recommended in metastatic, residual or recurrent cases of GISTs or which are surgically not removable; however, recent recommendations suggests the use of imatinib mesylate after radical surgery in high-risk cases, because it has shown a significant decrease in the recurrence rate, and the Food and Drug Administration (FDA) has also approved the use of imatinib as adjuvant therapy after complete resection of localized, primary GIST.

Occurrence of other tumors in patients with GIST

OBJECTIVE

Evaluate the presence of other tumors in cohort of patients with GIST treated at a cancer treatment referral center - INCA.

METHODS

We reviewed the medical records of patients diagnosed with GIST who were treated at INCA between 1998 and 2008. Immunohistological diagnosis was confirmed by a pathologist specialized in sarcomas. Patients presenting second non-GIST tumors were identified. Age, sex, tumor location, risk groups (according to the National Institutes of Health criteria), characteristics of non-GIST tumors and treatment results were analyzed.

RESULTS

Among the 101 patients diagnosed with GIST who were evaluated during the study period, 14 (13.8%) had other non-GIST tumors, 9 females (64.3%), with a median age of 68 years (10-79 years). The stomach was the location of GISTs in 8 cases (57.1%), followed by the small bowel in 4 cases (28.5%), colon and mesentery with 1 case (7.1%) each. The mean size of lesions was 4.79 cm (0.3-15 cm), with malignant potential low/very low in 7 cases (50%), intermediate in 5 cases (35.7%) and high in 2 cases (14.3%). The diagnosis of GIST was incidental in 6 cases and in one case the non-GIST tumor was incidental. The non-GIST tumors were most frequent in the stomach (adenocarcinoma), in 4 cases (28.5%) and colon/rectum (adenocarcinoma) in 4 other cases. The other sites involved were breast (ductal carcinoma), kidney (clear cell carcinoma), prostate (adenocarcinoma), endometrium (adenocarcinoma), ovary (adenocarcinoma) and adrenal (neuroblastoma), with one case each. The tumors were synchronous in 7 cases (50%). With a median follow-up after GIST resection of 41 months (2-87 months), 9 patients were alive without evidence of disease, 2 died due to GIST, 2 died due to non-GIST tumors and the remaining patient died due to postoperative complications.

CONCLUSIONS

We discovered a 13.8% incidence of non-GIST tumors in a series of 101 GIST cases under our care. This association should always be considered in the management of patients with GIST.

[Gastrointestinal stromal tumors in neurofibromatosis type 1]

Neurofibromatosis type 1 or Recklinghausen disease is one of the most common hereditary autosomal dominant diseases. The disease-causing gene can be found on chromosome 17 as an NF1 tumor suppressor gene. The mutation of this gene leads to the loss of tumor suppressor function, which in turn causes the development of benign and malignant tumors. In 25% of the cases gastrointestinal manifestations are found, most often GIST. The close correlation of the two diseases are well known in the literature, there are more than 160 published cases. GIST develops in 7% of patients with neurofibromatosis, and among these patients the occurrence of NF1 is 150-180 times more frequent than in the general population. Neurofibromatosis associated with GIST is a different entity and, unlike sporadic GIST, it is usually multiplex and almost always develops in the small bowel. There is a slightly higher incidence among women than in men, and the disease develops at young age. Histological characteristics include spindle cell type, skeinoid fibers and frequent S100 positivity. Low mitotic activity usually suggests better prognosis. c-KIT and PDGFRA mutation is very rare, in agreement with the hypothesis that the pathogenesis of NF1-GIST is not c-KIT dependent. It is presumed that neurofibromatosis associated and sporadic GIST have different pathogenesis, and that the development of GIST tumor in neurofibromatosis is part of the hereditary disease. c-KIT and PDGFRA mutations--as shown in a few known cases--probably develop at a later step of tumor genesis. Imatinib, which has revolutionized the therapy of GIST, cannot be used in this patient group, however, as of today not enough information is available.

Pancreatic insulinoma co-existing with gastric GIST in the absence of neurofibromatosis-1

Background

Gastrointestinal stromal tumours (GIST) frequently occur in patients with neurofibromatosis type 1 (NF-1). It has been reported that GIST may co-exist with pancreatic endocrine tumors but this has only been in association with NF-1.

Case presentation

A 76 year old woman presented with a 12 month history of hypoglycaemia symptoms. Abdominal CT scan demonstrated a 13 mm insulinoma localized in the tail of her pancreas. She was commenced on diazoxide and later underwent surgery for enucleation of insulinoma when a small (< 1 cm) incidental tumour was discovered on her stomach wall which was identified as GIST.

Conclusion

This is the first case report of a pancreatic insulinoma co-existing with a GIST in a patient without NF-1. In addition, we make the first report of rapidly growing cystic GIST recurrence following resection of a primary GIST tumour.

Gastric and prostate adenocarcinoma in a patient with metastatic gastrointestinal stromal tumor

BACKGROUND

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal malignancy of the gastrointestinal tract. Gastric cancer is the second most common neoplasm worldwide. Prostate cancer is the most common non-cutaneous cancer. The most frequently encountered second malignancies in patients with prostate adenocarcinoma include carcinomas of the bladder, stomach, and colon, followed by cutaneous and hematolymphoid malignancies.

CASE REPORT

We report the case of a 60-year-old male patient who was diagnosed with GIST and started on imatinib mesylate 400 mg/day. 2 years later, the patient was diagnosed with gastric adenocarcinoma, and a subtotal gastrectomy and gastrojejunostomy were performed. At followup 6 months later, prostate-specific antigen (PSA) levels were elevated, and a prostate biopsy showed a prostate adenocarcinoma.

CONCLUSION

This is the second report of metachronous prostate cancer, gastric cancer, and GIST in the English language literature.

Coexistence of gastrointestinal stromal tumors with other neoplasms

BACKGROUND

The purpose of this study was to assess the prevalence of other neoplasms in patients with gastrointestinal stromal tumors (GISTs) and to compare clinical and histopathological data in patients with a GIST and accompanying neoplasms and in patients with GIST only.

METHODS

The analysis encompassed 82 patients with a GIST from among 330 300 patients whose surgical specimens, biopsies, and autopsies were evaluated between January 1989 and June 2006. A subgroup of patients with other types of neoplasms was selected.

RESULTS

Other neoplasms in patients with a GIST were diagnosed in 22 of the 82 (26.8%) patients. The most common accompanying neoplasms were colorectal (nine cases) and gastric (four cases) adenocarcinoma, as well as pancreatic adenocarcinoma (three cases). There was a tendency toward more common localization of a GIST in the small intestine in patients with other neoplasms than in patients with a GIST alone (P < 0.09). Tumors with very low risk of aggressive behavior were more frequent in patients with a GIST accompanied by other neoplasms than in the other group (P < 0.05). No phenotypic differences in GIST cells were found between the two groups.

CONCLUSIONS

In almost 27% of the study population, GISTs coexisted with other neoplasms. A greater proportion of patients with a GIST localized in the small intestine and/or characterized by a very low risk of aggressive behavior and accompanying other neoplasms, compared with a GIST alone, most likely reflects the fact that in the first group, GISTs tended to be an incidental finding during surgery. The results were affected by patient selection and the type of tissue material available.

Multiple gastrointestinal stromal tumors and bilateral pheochromocytoma in neurofibromatosis

The coincidence of a gastrointestinal stromal tumor (GIST) and a neuroendocrine tumor (NET) in neurofibromatosis type 1 (NF1) is described only five times within the literature. We report on a 63 year old Caucasian female with the rare condition of neurofibromatosis type 1 coinciding with recurrent gastrointestinal stromal tumor plus bilateral pheochromocytoma (PCC). After a history of palpitations and dizziness that lasted for years, a left adrenal mass was detected by CT. Laparotomy revealed a pheochromocytoma of the left adrenal gland while an ileoterminal GIST was found incidentally intraoperatively. After six months contralateral PCC and multiple recurrent GIST were resected again. After four years the patient is doing well without any signs of further recurrent tumors. Discussion includes review of the literature.

Gastrointestinal stromal tumors in patients with neurofibromatosis 1: a clinicopathologic and molecular genetic study of 45 cases

Gastrointestinal stromal tumors (GISTs), the specific KIT- or PDFGRA-signaling driven mesenchymal tumors, most commonly occur sporadically, but there seems to be some increased tendency for these tumors to develop in patients with neurofibromatosis 1 (NF1). The clinicopathologic profile, KIT, and PDGFRA mutation status and long-term prognosis of patients with GIST in NF1 are incompletely characterized. In this study, we analyzed 45 patients who had NF1 and GIST. There were 26 females and 19 males with a median age of 49 years (10 years lower than the median age of GIST patients in general). A great majority of tumors occurred in the jejunum or ileum, with multiple tumors occurring in 28 cases. Ten patients had a duodenal and one had a gastric GIST. The most common presentations were gastrointestinal bleeding and anemia, and many patients had intermittent bleeding over several years. The majority of the tumors were small and mitotically inactive; only 7 had mitotic activity >5/50 HPFs and 15 tumors were >5 cm. Associated Cajal cell hyperplasia was common. One patient had an intraabdominal peri-intestinal neurofibroma. Five of 35 patients with follow-up died of metastatic disease; all of these had a tumor >5 cm, mitotic rate >5/50 HPFs, or both; three of these tumors were located in the duodenum. The presence of multiple small tumors was not associated with progressive disease. Most patients with long-term follow-up enjoyed a good prognosis; 2 died of other NF1-associated tumors (malignant peripheral nerve sheath tumors, brain tumor). None of the 16 tumors from 15 patients had a KIT exon 9, 11, 13, or 17 or PDGFRA exon 12 or 18 mutation as is typically seen in sporadic GISTs, indicating that GISTs in NF1 patients have a different pathogenesis than sporadic GISTs.