Laparoscopic resection of sporadic synchronous gastric and jejunal gastrointestinal stromal tumors: Report of a case

Multicentricity of gastrointestinal stromal tumors (GISTs) has been described only in patients with neurofibromatosis type 1 (NF1) or within the small intestine, and different pathogenetic mechanisms are involved. We report a case of synchronous sporadic gastric and jejunal GISTs, which were resected laparoscopically in a 67-year-old man. Immunohistochemical analysis revealed that both lesions were KIT (CD117)-positive, but that the gastric lesion was CD34-positive, whereas the jejunal one was Vimentin-, S-100-, and SMA-positive. Molecular analysis of mutations in KIT exons 9, 11, 13, and 17, and in PDGFRA exons 12 and 18 revealed the presence of a gastric sporadic GIST with a KIT mutation of the exon 11 and a jejunal sporadic GIST without KIT or PDGFRA mutations. To our knowledge, this is the first report of laparoscopically resected synchronous sporadic gastric and jejunal GISTs.     

Microscopic gastrointestinal stromal tumors in esophageal and intestinal surgical resection specimens: a clinicopathologic, immunohistochemical, and molecular study of 19 lesions

Microscopic gastrointestinal stromal tumors (GISTs) (synonyms: sporadic interstitial cell of Cajal hyperplasia, seedling GISTs, minimal GISTs) are common incidental findings in gastroesophageal resections (9% to 35%). To our knowledge, their frequency, clinicopathologic features, and molecular pathogenesis from nongastroesophageal sites have so far not been sufficiently analyzed. We studied 19 lesions from distal esophagus (n=8), gastroesophageal junction (n=2), sigmoid colon (n=5), and vermiform appendix, cecum, rectum, and small intestine (1 each). Microscopic GISTs were detected in 0.2%, 0.1%, and 0.01% of routinely processed resection specimens from sigmoid colon, vermiform appendix, and rectum, respectively. Patients were 11 men and 8 women with a mean age of 66 years (range, 57 to 86 y). Thirteen patients had GI cancers and 5 had diverticular disease. None has a family history of GIST or features of neurofibromatosis 1. Lesions were 0.5 to 4 mm in size (mean, 1.12 mm), were all spindled and had noncircumscribed infiltrating borders. All arose in the muscularis propria and 2 were predominantly subserosal. Immunohistochemistry revealed a CD117/CD34/smooth muscle actin-negative phenotype in 18/19 lesions. Three KIT exon 11 mutations (2 point mutations and 1 deletion, all involving W557) were detected in 3/12 lesions with successful molecular analysis. In conclusion, incidental microscopic GISTs are uncommon in intestinal resections (< or =0.1%), contrasting with their gastroesophageal counterparts (> or =9%). Somatic KIT mutations are early initiating molecular events in a subset of them. The remarkable variation in the incidence of microscopic GISTs at different GI sites suggests an origin from heterogeneous subsets of interstitial cells of Cajal with varying potentials for neoplastic transformation.     

Familial gastrointestinal stromal tumors caused by the novel KIT exon 17 germline mutation N822Y

Gastrointestinal stromal tumors (GISTs) are most often associated with oncogenic mutations of the KIT gene resulting in activation of the tyrosine kinase receptor KIT. Familial GIST syndrome based on a hereditary predisposition to develop GIST owing to a germline mutation is exceedingly rare. We describe a kindred with familial GIST displaying a novel germline mutation in exon 17. Three siblings (2 females, 1 male; 42 to 49 y) underwent surgery for multiple intra-abdominal tumors within a 3-year period. Their father had been operated on for gastric and jejunal tumors 20 years previously. The GIST was confirmed by immunohistochemistry in each sibling. Tumor and blood samples of the family members were analyzed for mutations in KIT and platelet-derived growth factor receptor (PDGFRalpha) genes. All examined lesions were of spindle cell type with expression of CD117. The tumor material exhibited a novel point mutation in codon 822 in exon 17 resulting in the replacement of asparagine by tyrosine (N822Y). The same mutation was detected in the father's blood sample. One healthy brother of the 3 siblings showed a wild-type sequence of the KIT gene. The germline mutation in exon 17 of the KIT gene identified in this kindred is very different from previously reported mutations of the KIT gene in familial GIST. Although the penetrance of KIT mutations is as yet unknown, assessment of the unaffected kindred of GIST patients for the presence of this mutation could help to distinguish individuals at high risk from those at virtually no risk.     

KIT-negative gastrointestinal stromal tumors: proof of concept and therapeutic implications

The diagnosis of gastrointestinal stromal tumor (GIST) is currently based on morphologic features and immunohistochemical demonstration of KIT (CD117). However, some tumors (in our estimation approximately 4%) have clinicopathologic features of GIST but do not express KIT. To determine if these lesions are truly GISTs, we evaluated 25 tumors with clinical and histologic features typical of GIST, but with negative KIT immunohistochemistry, for KIT and PDGFRA mutations using DNA extracted from paraffin-embedded tissue. Most tumors originated in the stomach (N = 14) or omentum/mesentery (N = 5). The neoplasms were composed of epithelioid cells (13 cases), admixed epithelioid and spindle cells (8 cases), or spindle cells (4 cases). Absence of KIT expression was confirmed by immunoblotting in 5 cases. Tumor karyotypes performed in 4 cases were noncomplex with monosomy 14 or 14q deletion, typical of GIST. Mutational analysis revealed PDGFRA and KIT mutations in 18 and 4 tumors, respectively, whereas 3 tumors did not have apparent KIT or PDGFRA mutations. The PDGFRA mutations primarily involved exon 18 (N = 15) and included 11 tumors with missense mutation in codon 842 (PDGFRA D842V or D842Y). In conclusion, a small subset of GISTs with otherwise typical clinicopathologic and cytogenetic features do not express detectable KIT protein. When compared with KIT-positive GISTs, these KIT-negative GISTs are more likely to have epithelioid cell morphology, contain PDGFRA oncogenic mutations, and arise in the omentum/peritoneal surface. Notably, some KIT-negative GISTs contain imatinib-sensitive KIT or PDGFRA mutations; therefore, patients with KIT-negative GISTs should not, a priori, be denied imatinib therapy.     

Multiple gastrointestinal stromal tumors: Clinicopathologic and genetic analysis of 12 patients

Multiple gastrointestinal stromal tumors (GISTs) are extremely rare and usually associated with type 1 neurofibromatosis and familial GIST. The aim of this study was to investigate the clinical, phenotypic, and genetic characteristics of multiple GISTs to gain insights into their underlying pathogenesis and clinical behavior. Forty-seven paraffin blocks of multiple GISTs from 12 patients were analyzed. Genomic DNA was extracted from the tumor and normal mucosa and mutations for 4 exons of KIT gene and 3 exons of PDGFRA gene were determined. Among 12 patients with multiple GISTs, 5 were sporadic, 2 were familial with germline mutations of KIT gene, and 5 were associated with type 1 neurofibromatosis. All but 1 sporadic and familial multiple GISTs showed mutations of KIT gene shared by the same mutation on each GIST mass within a patient. But in 1 sporadic case, different types of KIT mutations were observed. Two familial multiple GIST cases showed diffuse involvement of the gastrointestinal tract with diffuse hyperplasia of interstitial cell of Cajal. Multiple GISTs associated with type 1 neurofibromatosis were located in the jejunum and harbored no mutations of KIT or PDGFRA. Different types of KIT gene mutation found in our case raise a possibility that recurrence of GISTs within a gastrointestinal tract may have a chance to be a rare occurrence of multiple primary GISTs instead of true recurrence. Multiple GISTs show unique clinical, phenotypic, and genotypic characteristics that are dependent on the particular underlying mechanisms, but the overall prognosis is favorable regardless of the numbers or phenotype of GISTs.     

Minute gastric sclerosing stromal tumors (GIST tumorlets) are common in adults and frequently show c-KIT mutations

Multifocal hyperplasia of interstitial cells of Cajal (ICC hyperplasia) is a precursor of hereditary gastrointestinal stromal tumors (GISTs) in patients with germline mutations of c-KIT or PDGFRA, but precursor lesions of sporadic GISTs have not been defined yet. Small hyalinizing stromal tumors of the proximal stomach (referred to in this study as GIST tumorlets) were collected prospectively from 98 consecutive autopsies and additional cases were retrieved from surgical pathology files (total n=57). GIST tumorlets were grossly detectable in 22.5% consecutive autopsies performed in individuals older than 50 years. All lesions were located in the cardia, fundus, or proximal body, and ranged in size from 1 to 10 mm (4 mm). Similar lesions were not detected in the antrum, duodenum, and the remainder of the bowel. Histologically, the spindle cell subtype comprised all cases, with hyalinization and calcification in 57% of cases. The spindle cells were immunohistochemically positive for vimentin, CD117, and CD34. Twenty-four cases yielded sufficient DNA for subsequent molecular analysis, which showed c-KIT mutations in 11 cases (46%) and PDGFRA mutations in 1 case (4%). Sporadic GIST tumorlets of the proximal stomach are common in the general population over the age of 50 years and frequently show somatic c-KIT mutations. GIST tumorlets probably represent the grossly recognizable counterpart of sporadic ICC hyperplasia caused by somatic c-KIT or PDGFRA mutations. Early hyalinization and calcification seems to confer limited growth potential, and complete regression of such lesions is common. GIST tumorlets likely represent preclinical (preneoplastic) lesions that need additional stimuli to evolve into clinical GISTs, raising the possibility of a hyperplasia-neoplasia sequence in the development of sporadic GISTs.     

"Pediatric-type" gastrointestinal stromal tumors in adults: distinctive histology predicts genotype and clinical behavior

Gastrointestinal stromal tumors (GISTs) rarely affect children, mainly girls. Pediatric GISTs typically arise in the stomach as multifocal tumors with a multinodular growth pattern, epithelioid morphology, lymph node metastases, an absence of KIT and PDGFRA gene mutations, and indolent behavior. Occasional GISTs in adults show similar features. Such tumors are not widely recognized. GISTs with a multinodular growth pattern in patients over the age of 18 years were retrieved from surgical and consultation files. Hematoxylin and eosin-stained slides were reviewed, immunohistochemistry was performed, and KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12, 14, and 18) genes were screened for mutations. Clinical follow-up was obtained. Sixteen cases were identified, affecting 13 women and 3 men (median age, 31.5 y; range, 19 to 56 y), all in the stomach. The mean tumor size was 5.4 cm (range, 1.8 to 11 cm); 4 were multifocal. All tumors showed a multinodular or plexiform architecture and epithelioid (N=3) or mixed epithelioid and spindle cell (N=13) morphology. Five tumors had vascular invasion; 6 had focal necrosis. Mitotic activity ranged from 3 to 156/50 high-power fields (8 tumors had ≤5/50 high-power fields). Using Armed Forces Institute of Pathology risk stratification, categories for primary tumors were: none (N=2), very low risk (N=3), low risk (N=3), moderate risk (N=3), and high risk (N=5). By immunohistochemistry, all tumors were positive for KIT, 82% DOG1, 72% CD34, 18% caldesmon, 9% S-100, 8% smooth muscle actin, and 0% desmin. All tumors were wild type for KIT and PDGFRA in the exons that were screened. At primary resection, 9 patients (56%) had lymph node metastases and 3 patients had liver metastases. Follow-up ranged from 16 months to 16 years (median, 5 y). Two tumors recurred locally in the stomach and 7 patients developed subsequent metastases to the lymph nodes (N=5), liver (N=3), and peritoneum/omentum (N=3). Primary tumors from 7 patients with metastases were Armed Forces Institute of Pathology low risk, very low risk, or no risk of recurrence. None of the metastatic tumors responded to treatment with imatinib mesylate. One patient died of disseminated liver and intra-abdominal metastases and the remaining patients were alive at last follow-up. Gastric GISTs in adults with a multinodular or plexiform growth pattern and epithelioid or mixed morphology are similar to pediatric GISTs. Unlike conventional adult GISTs, this distinctive subset predominantly affects women, often metastasizes to lymph nodes, and lacks mutations in KIT and PDGFRA. Current risk assessment criteria do not reliably predict behavior for this group. Although metastases are common and most tumors are imatinib resistant, they pursue a relatively indolent clinical course. Recognition of "pediatric-type" GISTs in adults is critical for prognosis, appropriate therapy, and follow-up.     

Succinate dehydrogenase-deficient GISTs: a clinicopathologic, immunohistochemical, and molecular genetic study of 66 gastric GISTs with predilection to young age

Most gastrointestinal stromal tumors (GISTs) are driven by KIT or PDGFRA-activating mutations, but a small subset is associated with loss of function of the succinate dehydrogenase (SDH) complex of mitochondrial inner membrane proteins. This occurs by germline mutations of the SDH subunit genes and hitherto unknown mechanisms. SDH-deficient GISTs especially include pediatric GISTs and those associated with Carney triad (CT) or Carney-Stratakis syndromes (CSSs); the latter 2 also include paraganglioma as a component. SDH-deficient GISTs were identified in this study on the basis of immunohistochemical loss of succinate dehydrogenase subunit B (SDHB), which signals functional loss of the SDH complex. We found 66 SDH-deficient GISTs among 756 gastric GISTs, with an estimated frequency of 7.5% of unselected cases. Nearly, all gastric GISTs in patients <20 years, and a substantial percentage of those in patients <40 years, but only rare GISTs in older adults were SDH deficient. There was a female predominance of over 2:1. Two patients each had either pulmonary chondroma or paraganglioma (CT), but none of the examined cases had SDH germline mutations (CSS) or somatic KIT/PDGFRA or BRAF mutations. SDH-deficient GISTs were often multiple and typically showed plexiform muscularis propria involvement and epithelioid hypercellular morphology. They were consistently KIT-positive and DOG1/Ano 1-positive and almost always smooth muscle actin negative. Tumor size and mitotic activity varied, and the tumors were somewhat unpredictable with low mitotic rates developing metastases. Gastric recurrences occurred in 11 patients, and peritoneal and liver metastases occurred in 8 and 10 patients, respectively. Lymph node metastases were detected in 5 patients, but lymphovascular invasion was present in >50% of cases studied; these 2 were not related to adverse outcome. Seven patients died of disease, but many had long survivals, even with peritoneal or liver metastases. All 378 nongastric GISTs and 34 gastric non-GIST mesenchymal tumors were SDHB positive. SDH-deficient GISTs constitute a small subgroup of gastric GISTs; they usually occur in children and young adults, often have a chronic course similar to that of pediatric and CT GISTs, and have potential association with paraganglioma, necessitating long-term follow-up.     

Multicentric sporadic gastrointestinal stromal tumors (GISTs) of the stomach with distinct clonal origin: differential diagnosis to familial and syndromal GIST variants and peritoneal metastasis

Most sporadic gastrointestinal stromal tumors (GISTs) occur solitary, whereas a multicentric appearance is suspicious for a familial or syndromal setting such as with germline mutations of proto-oncogene tyrosine protein kinase Kit (KIT) or platelet derived growth factor receptor alpha (PDGFRA), or even for metastases. The aim of this study was to evaluate whether multicentric sporadic GISTs are of clonal origin. Four patients with 1 clinically apparent tumor (mean size 5.6 cm) and 1 to 3 further small incidental tumors (mean size 0.7 cm) were analysed by mutation analysis and comparative genomic hybridization for mutations of KIT and PDGFRA and chromosomal imbalances in their tumors. No clinicopathologic features have been found being indicative of one of the established familial or syndromal GIST variants. Each of the small GISTs were localized in the muscularis propria, and were visible from the serosal but not from the mucosal side. Different mutations of KIT and PDGFRA were present among individual tumors of each patient, and germline mutation of KIT and PDGFRA could be excluded. Comparative genomic hybridization revealed a mean count of 7 chromosomal imbalances in the clinically apparent tumors compared with a mean count of 0.3 in the small incidental counterparts. Sporadic GISTs can appear multicentric by coincidence. They are an important differential diagnosis to familial and syndromal GIST variants, or even to peritoneal metastases. Different mutations of KIT and PDGFRA among individual tumors in 1 patient refer to different clonal origin of multicentric sporadic GISTs. The type of mutation of KIT and PDGFRA was independent of tumor size, whereas small GISTs <1 cm rarely had genomic imbalances.     

胃肠间质瘤基因突变和分子靶向治疗相关研究进展

胃肠管间质瘤是最常见的胃肠管原发的间叶源性肿瘤.胃肠管间质瘤的发生是由KIT基因突变导致KIT蛋白的组成性激活引起的.血小板源性生长因子受体α(platelet-derived growth factor receptor alpha,PDGFRA)也与胃肠管间质瘤的发病机制有关.KIT的突变位点主要是exon11、exon9、exon13和exon17;PDGFRA的突变位点主要是exon18、exon12和exon14.胃肠间质瘤的临床病理参数、对甲磺酸依马替尼的反应与突变所在的位置及突变类型相关.甲磺酸伊马替尼是一个选择性的小分子酪氨酸激酶抑制剂,其临床应用是胃肠管间质瘤分子靶向治疗的里程碑.本文就胃肠管间质瘤基因突变和分子靶向治疗的研究进展概述.     

Gastrointestinal stromal tumors of the stomach: a clinicopathologic, immunohistochemical, and molecular genetic study of 1765 cases with long-term follow-up

Gastrointestinal (GI) stromal tumors (GISTs), the specific KIT- or PDFGRA-signaling driven mesenchymal tumors, are the most common mesenchymal tumors of the GI tract. In this study, we analyzed 1869 cases originally classified as smooth muscle tumors of the stomach and found that 1765 (94%) of these were GISTs. The GISTs had a slight male predominance (55%) with a median age of 63 years. Only 2.7% of tumors occurred before the age of 21 years and 9.1% before the age of 40 years. The tumors varied from 0.5 to 44 cm (median, 6.0 cm) and most commonly presented with GI bleeding; 12% were incidentally detected. Several histologic variants were recognized among the spindle cell tumors (sclerosing, palisaded-vacuolated, hypercellular, and sarcomatous) and of epithelioid tumors (sclerosing, dyscohesive, hypercellular, and sarcomatous). Outcome was strongly dependent on tumor size and mitotic activity. Only 2% to 3% of tumors <10 cm and <5 mitoses/50 HPFs metastasized, whereas 86% of tumors >10 cm and >5 mitoses/50 HPFs metastasized. However, tumors >10 cm with mitotic activity <5/50 HPFs and those <5 cm with mitoses >5/50 HPFs had a relatively low metastatic rate (11% and 15%). A small number of patients survived intra-abdominal metastasis up to over 20 years. Tumor location in fundus or gastroesophageal junction, coagulative necrosis, ulceration, and mucosal invasion were unfavorable factors (P <0.001), whereas tumor location in antrum was favorable (P <0.001). KIT expression was detected in 91% of the cases, CD34 in 82%, smooth muscle actin in 18%, and desmin in 5%; the latter two were favorable (P <0.001). KIT exon 11 mutations were detected in 119 cases; patients with point mutations fared better than those with deletions (P <0.01). PDGFRA exon 18 mutations (total 86 cases) were common in epithelioid GISTs and most commonly represented a D842V point mutation; none of these was prognostically significant. The above results may be helpful for setting the criteria for adjuvant treatment such as Gleevec.     

Gastrointestinal stromal tumors of neurofibromatosis type I (von Recklinghausen's disease)

Gastrointestinal stromal tumor (GIST), as well as the hyperplastic lesions of intestinal neural tissue and its supporting structures, is a gastrointestinal complication of type 1 neurofibromatosis (NF1) (von Recklinghausen's disease). In the present study, we analyzed the histologic and immunohistochemical features, and the c-kit and PDGFRA gene mutations of 36 GISTs derived from 9 NF1 patients. Distinctively, multiple GISTs arose preferentially in the small intestine. The histologic features of NF1-associated GISTs are almost similar to those of non-NF1 GISTs, but characteristically most of the NF1-associated GISTs contained skeinoid fibers. Thirty-three GISTs (92%) showed immunoreactivity for KIT, and 23 tumors (64%) showed diffuse or mosaic-like immunoreactivity for S-100 protein. Hyperplasic lesions, which may be the hyperplasia of interstitial cells of Cajal, were observed around some GISTs. Exons 9, 11, 13, and 17 of the c-kit gene and exons 12 and 18 of the PDGFRA gene were amplified and directly sequenced. Point mutations of c-kit gene or PDGFRA gene were identified only in three (8%) and two (6%) tumors, respectively. NF1-associated GISTs, showing the dual differentiation of interstitial cells of Cajal and Schwann cells, develop in close association with the myenteric nerve structure of gastrointestinal tract of NF1 patients. The point mutations of c-kit and PDGFRA gene may play a limited role in the tumorigenesis of NF1-associated GISTs.     

Gastrointestinal stromal tumors of the jejunum and ileum: a clinicopathologic, immunohistochemical, and molecular genetic study of 906 cases before imatinib with long-term follow-up

Gastrointestinal (GI) stromal tumors (GISTs), the specific KIT- or PDFGRA-signaling driven mesenchymal tumors, are the most common mesenchymal tumors of the GI tract. This study analyzed 1091 tumors originally classified as smooth muscle tumors of the small intestine (including jejunum or ileum and excluding duodenum), and found that 906 (83%) of these were GISTs. The GIST patients had 55:45 male-to-female ratio with a median age of 59 years (range, 13-94 years). Only 0.6% of tumors occurred before the age of 21 years and 13.6% before the age of 40 years. The tumors varied from 0.3 to 40 cm (median, 7.0 cm) and most commonly presented with GI bleeding or acute abdomen; 18% were incidentally detected. Histologically, the tumors were relatively monotypic with spindle cell (86%), epithelioid (5%), or mixed patterns (9%). Skeinoid fibers were present in 44% of cases, and their presence was associated with a favorable course. Most epithelioid tumors were malignant, and this morphology sometimes emerged from less cellular and less mitotically active spindle cell tumors, suggesting that it represented a transformation. KIT was immunohistochemically detected in 98%, CD34 in 40%, smooth muscle actin in 34%, desmin in 0.2%, and S-100 protein in 14% of the tumors tested. Outcome was strongly dependent on tumor size and mitotic activity, with an overall 39% tumor-related mortality, twice that for gastric GISTs. Only <3% of tumors <5 cm and < or = 5 mitoses/50 HPF metastasized, whereas 86% of tumors >10 cm and >5 mitoses/50 HPF metastasized. In stark contrast to corresponding gastric tumors, tumors >10 cm with mitotic activity < or = 5/50 HPF and those < or = 5 cm with mitoses >5/50 HPF had a high metastatic rate (>50%); tumors >5 cm < or = 10 cm with low mitotic rate had a 24% metastatic rate. The median survival times of patients with low mitotic rate tumors who died of disease decreased by increasing tumor size. KIT exon 11 mutations were detected in 90 cases, exon 9 mutation in 17 cases, and exon 17 mutation in 1 case; the presence of mutation or mutation type was not prognostically significant. There were no PDGFRA exon 12 or 8 mutations. Systematic data on prognosis of small intestinal GISTs of various size and mitotic activity categories can be helpful in management and surveillance of patients with these tumors.     

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.     

Gastrointestinal stromal tumors,intramural leiomyomas,and leiomyosarcomas in the duodenum: a clinicopathologic,immunohistochemical, and molecular genetic study of 167 cases

In this study we analyzed the clinicopathologic features of duodenal smooth muscle or stromal tumors, including 156 GISTs, 6 leiomyomas (LMs), and 5 leiomyosarcomas (LMSs) from the files of the Armed Forces Institute of Pathology and the Haartman Institute of the University of Helsinki. GISTs were documented as KIT positive (n = 109); 47 tumors were also included because of their histologic identity to KIT-positive cases. GIST-specific c-kit gene mutations were documented in exon 11 in 9 of 30 cases (30%) and exon 9 in 4 of 30 cases (13%). The GISTs occurred in patients with an age range of 10-88 years (median 56 years); 54% were male. Ten patients had neurofibromatosis type I; six of them had multiple GISTs. The GISTs ranged from small asymptomatic intramural or external nodules to large masses that extended into the retroperitoneum (median size 4.5 cm). They were mostly spindle cell tumors; three malignant GISTs had an epithelioid morphology, and 81 cases had skeinoid fibers. The tumors often coexpressed CD34 and KIT (54%) and were variably positive for smooth muscle actin (39%) and S-100 protein (20%) but never for desmin. A total of 86% of patients with tumors >5 cm with >5 mitoses/50 high power fields (HPF) (n = 21) died of disease, whereas no tumor <2 cm with <5 mitoses/50 HPF (n = 12) recurred or caused death. Long latency was common between primary operation and recurrences or metastases; either one occurred in 49 of 140 patients with follow-up (35%). No formula could accurately predict metastases, which occasionally developed even if mitotic activity was <5/50 HPF and size <5 cm. Metastases were in the abdominal cavity, liver, and rarely in bones and lungs but never in lymph nodes. Four actin- and desmin-positive and KIT-negative benign intramural LMs were similar to those more often seen in the esophagus. There were five LMSs, one of which formed a polypoid intraluminal mass; all were actin positive and KIT negative. The great majority of duodenal mesenchymal tumors are GISTs, which have a spectrum from small indolent tumors to overt sarcomas. LMs and LMSs are rare.     

Genetics of Gastrointestinal Stromal Tumors: A Heterogeneous Family of Tumors?

Approximately 85–90% of adult gastrointestinal stromal tumors (GISTs) harbor KIT and PDGFRA mutations. The remaining cases, including the majority of pediatric GISTs, lack these mutations, and have been designated as KIT/PDGFRA wild-type (WT) GISTs. Nearly 15% of WT GISTs harbor BRAF mutations, while others arise in patients with type I neurofibromatosis. Recent work has confirmed that 20–40% of KIT/PDGFRA WT GISTs show loss of function of succinate dehydrogenase complex. Less than 5% of GISTs lack known molecular alterations (“quadruple-negative” GISTs). Thus, it is important to consider genotyping these tumors to help better define their clinical behavior and therapy.     

Rhabdomyosarcomatous differentiation in gastrointestinal stromal tumors after tyrosine kinase inhibitor therapy: a novel form of tumor progression

Approximately 80% of advanced metastatic gastrointestinal stromal tumors (GISTs) respond to treatment with the tyrosine kinase inhibitor (TKI) imatinib mesylate. However, the majority of patients suffer disease progression at a median of 2 years due to drug resistance. In general, progressing GISTs retain their typical morphology. Herein, we report 5 cases of progressing metastatic GIST with heterologous rhabdomyoblastic differentiation after TKI treatment. Histologic, immunohistochemical, and mutational analyses were performed on histologically classic GISTs and components with rhabdomyoblastic differentiation. There were 3 men and 2 women (ranging from 35 to 66 y of age). Three tumors were localized at presentation (2 stomach and 1 small bowel) and 2 presented with metastases. All localized primary tumors were high risk. Two tumors showed spindle cell morphology and 3 were epithelioid, including 1 with marked pleomorphism. After resection of the 3 localized primary tumors, intra-abdominal (2 patients) and liver (1 patient) metastases developed. All patients were treated with imatinib and showed partial clinical responses (4 patient) or stable disease (1 patient). Four patients subsequently progressed; 2 patients were treated with sunitinib after progression with minor responses. Four patients underwent surgical debulking. At last follow-up (range: 20 to 87 mo), 2 patients died of disease, 2 were alive with metastatic disease resistant to TKIs, and 1 was alive without evidence of disease. In all cases, rhabdomyoblastic differentiation was identified adjacent to areas with classic GIST morphology in at least 1 metastatic site; in 1 case, the primary tumor (after treatment with TKIs) showed heterologous differentiation. The rhabdomyoblastic components showed strong and diffuse positivity for desmin and expressed myogenin, whereas KIT was negative in the rhabdomyoblastic component in all cases. Primary KIT mutations were detected in both the conventional GIST and rhabdomyoblastic components from all patients: KIT exon 11 mutations in 4 cases and a platelet-derived growth factor receptor alpha gene exon 18 deletion in 1 case. No secondary mutations of the type associated with TKI resistance were identified in the rhabdomyoblastic areas. This is the first report of rhabdomyoblastic differentiation occurring in GISTs that progressed on TKI therapy. It is associated with loss of KIT expression, but retention of the receptor tyrosine kinase mutation of the precursor GIST. The rhabdomyoblastic differentiation can represent a diagnostic pitfall. The molecular mechanisms for this form of TKI-resistant clonal evolution remain to be determined.     

Gastrointestinal stromal tumors of the stomach in children and young adults: a clinicopathologic, immunohistochemical, and molecular genetic study of 44 cases with long-term follow-up and review of the literature

Gastrointestinal stromal tumors (GISTs), specific KIT- or PDFGRA-signaling driven mesenchymal tumors, are rare in children and young adults, and their clinicopathologic and molecular genetic profile is incompletely understood. In this study, we analyzed 44 gastric GISTs occurring by the age of 21 years. There were 32 females and 12 males, youngest of whom were a 5-year-old boy and an 8-year-old girl. All but 1 of 25 patients under the age of 16 were girls. The patients most commonly received medical attention because of chronic, insidious gastrointestinal bleeding with anemia, less commonly with acute GI bleeding. Only 1 patient had Carney triad with pulmonary chondroma. None of the patients had family members with GIST. The tumors measured from 1.5 to 24 cm (median, 5.6 cm). A total of 21 tumors with specified location were in the antrum and 8 were in the gastric body. Histologically, 26 tumors were composed of epithelioid cells, 12 of spindle cells, and 6 of combination thereof. Mitotic activity varied form 0 to 65/50 HPF (median, 5/50). All but one of the 24 tumors tested were KIT-positive, and 20 were CD34-positive. Eleven patients developed liver or abdominal metastases, and 6 of them died of tumor surviving 5.5 to 35.5 years (median, 16 years) after the first surgery; three of these tumors had a low mitotic activity and size <10 cm. Twenty-one patients were alive with no evidence for disease 7 to 41 years (median, 17 years) after the first surgery. None of the 13 tumors examined (7 of them 8- to 16-year-old females) had KIT exon 9, 11, 13, or 17 or PDGFRA exon 12 or 18 mutation as typically seen in adult GISTs. Gastric GISTs in children have mainly epithelioid morphology, often occur in antrum, and have a somewhat unpredictable but slow course of disease. Their pathogenesis may differ from that of adult GISTs because no KIT or PDGFRA mutations were found; connection with Carney triad seems infrequent despite demographic and histologic similarities.     

Gastrointestinal stromal tumors in the appendix: a clinicopathologic and immunohistochemical study of four cases.

Mesenchymal tumors of the appendix are very rare, and specific stromal tumors (i.e., gastrointestinal stromal tumors, GISTs) have not been reported in this location to date. Four GISTs were identified in the review of primary mesenchymal tumors of the appendix from the files of the Armed Forces Institute of Pathology from 1970 to 1998. There were also one benign schwannoma, one diffuse neurofibroma with neurofibromatosis 1, one leiomyosarcoma in a child with HIV infection, and one inflammatory fibroid polyp. The four appendiceal GISTs occurred in adult males 56-72 years of age (mean 63 years). Two tumors occurred in patients who had surgery for appendicitis-like symptoms: one was an incidental finding during surgery for a malignant gastric epithelioid GIST and one was an incidental autopsy finding. Only one of the two appendices operated for symptoms had acute inflammation, and a polypoid GIST projected outward from the proximal part of appendix. Three tumors were partially obliterating nodules, eccentrically expanding the appendiceal wall. All four were spindle cell tumors, and three of them contained extracellular collagen globules (skeinoid fibers); none had atypia or mitotic activity (<1/50 high power fields). Immunohistochemically, two tumors studied were positive for CD117 (KIT), and two were positive for CD34. The tumors were negative for alpha-smooth muscle actin and S-100 protein. Follow-up revealed death from cardiovascular disease in one case (4 years after appendectomy) and liver failure because of malignant gastric epithelioid GIST metastatic to liver in another case 15 years after the appendectomy. This report documents the rare occurrence of CD117-positive GISTs as primary appendiceal tumors.     

Mutations in exon 11 of the c-kit gene in a myogenic tumor and a neurogenic tumor as well as in gastrointestinal stromal tumors. Utility of c-kit mutation as a prognostic biomarker for gastrointestinal mesenchymal tumor

BACKGROUND/AIMS: Gain-of-function mutations in exons 9, 11 and 13 of the c-kit gene in gastrointestinal stromal tumors (GISTs) have been identified, and it has been reported that the prognosis is worse for patients with mutation-positive GISTs than for those with mutation-negative GISTs. We studied c-kit mutations in gastrointestinal mesenchymal tumors. By chance, the c-kit mutation in exon 11 was found in myogenic and neurogenic tumors as well as in GISTs. Furthermore, we studied the clinical prognostic utility of these mutations. METHODS: Ten gastrointestinal mesenchymal tumors were stained with HE and immunohistochemically analyzed with alpha-smooth muscle actin, S-100 protein, CD34 and c-kit. In these tumors, as well as in 11 cases of leiomyomas, PCR-amplified DNA from the juxtamembrane (JM) domain of exon 11, the extracellular domain of exon 9 and the tyrosine kinase domain 1 of exon 13 showed a high frequency of c-kit mutation and was sequenced. RESULTS: Although c-kit mutations have previously been reported only in GISTs, we found c-kit mutations in the JM domain of exon 11 in one myogenic and one neurogenic tumor as well as in two GISTs. No c-kit mutation was seen in the 11 cases of leiomyomas. In addition, all four cases with c-kit mutation in exon 11 suffered a relapse sooner than the other cases without c-kit mutations. CONCLUSION: Clinically, the prognosis was worse for the patients with mutation-positive gastrointestinal mesenchymal tumors than for those with mutation-negative tumors. We therefore conclude that the gain-of-function mutation in exon 11 of the c-kit gene is an important prognostic factor for gastrointestinal mesenchymal tumors, including myogenic and neurogenic tumors as well as GISTs.