Gastrointestinal autonomic nerve tumor: immunohistochemical and molecular identity with gastrointestinal stromal tumor

Retroperitoneal extra gastrointestinal stromal tumor: A case report

INTRODUCTION

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors. Researchers do not know precisely what leads to GISTs, but genetic mutations play an important role. These mutations have no apparent cause. GISTs are usually asymptomatic tumors, although GI bleeding and weight loss can occur. CT is preferred for investigating potential GISTs.

CASE PRESENTATION

A 36-year-old unmarried Syrian female came to the hospital complaining of recurrent abdominal pain. CT revealed a large mass occupying a significant portion of the left hypochondrium and the lower part of the epigastrium. The tumor exceeded the median line to the right, pressing on the mesenteric vessels and the intestinal loops below. Immunohistochemistry results showed moderate positivity to CD117 and CD34, which were compatible with the diagnosis of GIST. The entire mass was excised. Physicians performed CT follow-ups every three months for 18 months, and no evidence of recurrence was observed.

DISCUSSION

Extragastrointestinal GISTs are a rare subtype of GISTs that occur outside the GI tract. GISTs previously used to be misdiagnosed as leiomyoma, leiomyosarcoma, leiomyoblastoma, and schwannoma. Treatment depends on surgery with adjuvant therapy tyrosine kinase inhibitors. Follow-up is recommended as the risk of recurrence is high.

CONCLUSION

We recommend that GIST, as an extremely rare tumor, should be considered in the differential diagnoses of masses that occur in the extra-intestinal region. Usually, patients need surgery with lymph node resection. However, this was not needed in our case.

Review of pathological findings in laparoscopic sleeve gastrectomy specimens performed for morbid obesity

BACKGROUND

Bariatric surgical procedures are employed when there is a failure of lifestyle modification in arresting obesity. Laparoscopic sleeve gastrectomy (LSG) is quickly becoming the bariatric surgical procedure of choice. LSG results in a gastric remnant that is subject to pathological examination. The objective of this paper is to review the literature in regard to histological findings identified in gastric remnants post-LSG and identify the most pertinent histological findings.

MATERIALS AND METHODS

A literature search was performed to identify relevant case series. Data gathered from relevant case series then underwent statistical analysis.

RESULTS

The most common histological findings in an LSG specimen were clinically indolent findings such as no pathological abnormalities identified followed by non-specific gastritis. A minority of cases demonstrated clinically actionable findings for which Helicobacter pylori represented the majority of these findings.

CONCLUSION

There is a broad spectrum of pathological findings in LSG specimens, ranging from clinically indolent to clinically actionable. The most common histological findings are clinically indolent and only a small portion are of clinical significance and, hence, actionable.

A ganglion-rich gastrointestinal stromal tumor: A case report

We report a case of an extremely rare type of duodenal gastrointestinal stromal tumor (GIST) that included neuronal components. Although gastrointestinal autonomic nerve tumors (GANTs), a subtype of GISTs, exhibit ultrastructural features of the nerve plexus, neuronal cells have not been observed within GANTs or GISTs. GISTs originate from interstitial cells of Cajal (ICCs), which are markedly different from the progenitor cells of neural elements and neural-crest-derived stem cells. This may explain why GISTs typically lack neuronal elements. It remains unclear that the neuronal components of this tumor are neoplastic or hyperplastic, but proliferation and survival of ICCs have recently been reported to be closely related to neurons. Although we could not find the KIT, PDGFR, and BRAF mutation as far as we examined, it may have had a rare mutation in NF1, a fusion of EVT6-NTRK3, or an as-yet-unknown KIT mutation that affected neurogenesis. Further investigation of related genetic mutations and accumulation of data from other similar cases is needed.

Small Periampullary Duodenal Gastrointestinal Stromal Tumor Treated by Local Excision: Report of a Case

Gastrointestinal stromal tumors (GIST) are mainly located in the stomach and the small bowel, with the duodenum accounting for about 4%. We report the case of a 66-year-old woman with a periampullary GIST of the duodenum that was treated by local excision and direct duodenal wall defect repair. Since no definitive clinical criteria have been established to differentiate malignant from benign mesenchymal tumors, preoperative cytology was not available and surgical removal of the 3.5 cm tumor was feasible, the patient was treated conservatively. The morbidity and mortality rates of the more radical and invasive duodenopancreatectomy, in particular when dealing with a soft pancreatic stump with a narrow pancreatic duct, are, in our opinion, too high for a potentially benign disease when the more conservative procedure is feasible. Four years after surgery the patient is doing well and control CT scan showed the absence of local recurrence.

A Clinical case of Duodenal Gastrointestinal Stromal Tumor with a Peculiarity in the Surgical Approach

We describe a case of duodenal, third portion, segmental resection for gastrointestinal stromal tumor. A 76-year-old man was referred for gastrointestinal bleeding, dyspnea and asthenia. Esophagogastroduodenoscopy showed a duodenal bleeding fistula. Computerized tomography demonstrated a retroperitoneal mass that compressed and displaced forward the third duodenal tract. Segmental resection of the third portion of the duodenum with a subtotal gastrectomy was performed. The patient was reconstructed with a termino-terminal duodenal anastomosis of the second and the fourth tract and with a Roux-en-Y gastrojejunum anastomosis. There were no postoperative complications. This duodenectomy procedure could be useful as a less extensive resection for duodenal gastrointestinal stromal tumor located in the third portion of the duodenum when the tumor is well capsulated, when the surrounding structures are not infiltrated and when there are no vascular difficulties. The technique reduces the morbidity and mortality correlated with duodenocefalopancreasectomy and improves postsurgical quality of life without worsening the risk of recurrence.

Neural and neurogenic tumours of the gastroenteropancreaticobiliary tract

Neural lesions occur uncommonly in the gastroenteropancreaticobiliary tract. However, due to the growing number of screening colonoscopy procedures, polypoid neural lesions of the colon are being recognised increasingly and range from benign tumours to high-grade malignant neoplasms. Morphological variability of neural tumours can be wide, although some entities share pathological features, and, as such, these lesions can be diagnostically challenging. We review the spectrum of pathology of neural tumours in the gastroenteropancreaticobiliary tract, with the goal of providing a practical approach for practising surgical pathologists.

Clinical and pathological characteristics of gastrointestinal stromal tumor (GIST) metastatic to bone

Our aim in this study was to describe the clinical, morphological, and molecular profile of gastrointestinal stromal tumor (GIST) metastatic to bone. We analyzed the morphological, phenotypic, and molecular characteristics of seven cases, and in addition reviewed 17 cases from literature. Sequence analysis of KIT and PDGFRA genes was possible for six cases. For the GIST cases with bone metastasis, the most common primaries were small intestine (29%), stomach (25%), and rectum (21%). Sites of bone metastases were vertebrae (11), pelvis (8), femur (8), ribs (6), humerus (5), skull (3), scapula (1), and mandible (1). The size ranged from 1.5 to 13 cm (median, 3.8 cm). Bone metastases without involvement of any other organ were seen in 17% of the cases and were solitary in 14 (58%). Adjacent soft tissue involvement was present in nearly half of the patients. Bone metastasis was either manifest at the time of diagnosis (28%) or occurred after a mean period of 4.7 years (3 months-20 years). Morphologically, neoplastic cells were spindle in 67%, epithelioid in 13%, and mixed epithelioid and spindle in 20%. CD117, DOG1, and CD34 were positive in 88, 86, and 85% of the cases, respectively. KIT Exon 11 mutations were the most frequent gene alteration (78%), followed by KIT Exon 13 mutations. Of 17 of the cases with available follow-up information, 7 (41%) patients developed bone metastasis under imatinib therapy. Five patients (29%) died of disease within a mean of 17 months. Bone metastases from GIST are usually found in patients with advanced disease and typically present as lytic masses with occasional soft tissue involvement. We could not identify any KIT or PDGFRA alterations predisposing to bone metastasis.

Clinical implications of proliferation activity in T1 or T2 male gastric cancer patients

Proliferation activity has already been established as a prognostic marker or as a marker for anticancer drug sensitivity. In gastric cancer, however, the prognostic significance of proliferation activity is still being debated. Several studies evaluating proliferation activity using Ki-67 have shown controversial results in terms of the relationship between proliferation activity and overall survival (OS) or drug sensitivity in gastric cancer patients. Because cytoskeleton-associated protein 2 (CKAP2) staining has recently been introduced as a marker of proliferation activity, we analyzed 437 gastric cancer tissues through CKAP2 immunohistochemistry, and we evaluated the chromatin CKAP2-positive cell count (CPCC) for proliferation activity. Although the CPCC did not show any significant correlation with OS in the male, female or total number of cases, it did show a significant correlation in the T1 or T2 male patient subgroup, according to log-rank tests (P=0.001) and univariate analysis (P=0.045). Additionally, multivariate analysis with the Cox proportional hazard regression model showed a significant correlation between the CPCC and OS (P=0.039) for the co-variables of age, gender, T stage, N stage, histology, tumor location, tumor size and adjuvant chemotherapy. In male gastric cancer cell lines, faster-growing cancer cells showed higher sensitivity to cisplatin than slow-growing cells. Thus our study indicates that CPCC-measured proliferation activity demonstrates a significantly worse prognosis in T1 or T2 male gastric cancer patients. The CPCC will help to more precisely classify gastric cancer patients and to select excellent candidates for adjuvant chemotherapy, which in turn will facilitate further clinical chemotherapeutic trials.

Gastrointestinal autonomic nerve tumors: a clinical review

PURPOSE

Gastrointestinal autonomic nerve tumors (GANTs) are believed to be rare accounting for 1 % of all malignant gastrointestinal tumors. Many gastrointestinal surgeons and gastroenterologists are unaware of this entity. This review aims to highlight the salient clinical features and prognosis of GANTs.

METHODS

Using the common search engines and manual cross-referencing, a search of the English literature was conducted for "gastrointestinal autonomic nerve tumor."

RESULTS

All of the published literature on GANTs is either case reports or small case series. From 49 retrieved articles, a total of 107 GANT cases were collected with a mean age of 54 years and equal male to female preponderance. The most commonly affected site was small bowel followed by stomach. Esophageal and colorectal GANTs were less frequent. Clinical presentation was variable ranging from non-specific symptoms, abdominal pain, weight loss, iron-deficiency anemia, to obstruction and gastrointestinal bleeding. Acute presentation due to free rupture or perforation with subsequent peritonitis was extremely rare. Endoscopic and radiological investigations were valuable in tumor localization and determination of distant spread. Thirteen patients were lost to or had no follow-up, leaving 94 patients for long-term outcome analysis. All patients were treated by radical surgical resection of the involved organ as this offered the only hope of cure. Local recurrence, metastases, or both developed in 40 % of cases despite radical surgical resection. Resection for local recurrences and hepatic metastases was feasible in some selected cases. Response to adjuvant chemoradiation was poor and imatinib mesilate was effective in cases of metastatic or inoperable CD117-positive GANTs.

CONCLUSION

Radical surgical resection of GANTs is the mainstay of treatment. The aggressive behavior after radical resection coined with the poor response to adjuvant chemotherapy call for the urgent need to develop new adjuvant therapies.

Gastric Schwannoma: A Case Report and Review of Literature

Schwannomas are usually benign, slow growing tumors, that originate from any nerve that has a Schwann cell sheath. Here, we report the case of a 40 year-old female patient with an incidentally noted submucosal gastric tumor while being evaluated for cervical lymphadenopathy as a part of workup for lymphoma. She underwent sleeve resection of the stomach under suspicion of a gastrointestinal stromal tumor, but postoperative histopathological and immunohistochemical findings confirmed the diagnosis of shwannoma. Although schwannomas are mostly benign, they are often indistinguishable preoperatively from malignant tumors such as gastrointestinal stromal tumors. Therefore, resection is the treatment of choice for all such tumors.

The ubiquitous neural cell adhesion molecule (N-CAM)

Adhesive interactions are important for cell trafficking, differentiation, function and tissue differentiation. Neural cell adhesion molecule (NCAM) is involved in a diverse range of contact-mediated interactions among neurons, astrocytes, oligodendrocytes, and myotubes. It is widely but transiently expressed in many tissues early in embryogenesis. Four main isoforms exist but there are many other variants resulting from alternative splicing and post-translational modifications. This review discusses the actions and association of N-CAM and variants, PSA CAM. L1CAM and receptor tyrosine kinase. Their interactions with the interstitial cells of Cajal – the pacemaker cells of the gut in the manifestation of gut motility disorders, expression in carcinomas and mesenchymal tumours are discussed.

Gastrointestinal autonomic nerve tumor of the stomach

Patient: Female, 32

Final Diagnosis: Gastrintestinal Autonomic Nerve Tumor (GANT)

Symptoms: anemia • anorexia • fatigue • fever • hearburn • nausea • weight loss

Medication: —

Clinical Procedure: —

Specialty: Gastroenterology and Hepatology

Establishment and characterization of novel cell lines and xenografts from patients with gastrointestinal stromal tumors

At present, no suitable GIST model exists for the analysis of drug resistance or metastasis using established human gastrointestinal stromal tumor (GIST) cell lines or xenografts even though the molecular mechanisms of drug resistance, progression and metastasis require clarification. The aim of this study was to establish and characterize human GIST cell lines and xenografts that can be used for evaluating drug resistance or various new molecularly targeted therapies. GIST tissues from patients were cultured and implanted under the skin of NOG (NOD/Shi-scid, IL-2Rrnu) mice. Two new cell lines (GK1C and GK3C) and three xenografts (GK1X, GK2X and GK3X) were generated from these clinical samples. The established GIST cell lines and xenografts were investigated for tumorigenesis and imatinib sensitivity. These cell lines and xenografts showed characteristic GIST morphology and exhibited KIT expression profiles similar to those of the patient samples. In addition, these GIST cell lines and xenografts were sensitive to imatinib. In conclusion, new human GIST cell lines and xenografts were established and maintained through repeated passages. These models will enable further study of combination therapies and the mechanisms of resistance, and allow testing of novel targeted monotherapies and combination therapies.

Primary leiomyosarcomas of the gastrointestinal tract in the post-gastrointestinal stromal tumor era

Most mesenchymal neoplasms of the gastrointestinal tract are currently classified as gastrointestinal stromal tumors (GIST). Gastrointestinal stromal tumors are diagnosed by immunopositivity for CD117, CD34, and DOG1.1, with or without molecular analyses. According to the World Health Organization classification, the diagnosis of primary leiomyosarcomas of the gastrointestinal tract is so rare that there are no significant data on demographic, clinical, or gross features of this tumor. A comprehensive literature search was performed to identify gastrointestinal leiomyosarcomas. Searches were limited to the past 12 years because definitive tools to differentiate leiomyosarcomas from GIST were introduced in the late 1990s. Cases were included only if convincing data were presented. Six cases of esophageal leiomyosarcoma and 5 cases of gastric leiomyosarcoma were confirmed. Furthermore, 26 cases of leiomyosarcoma of the small bowel, 11 cases of the colon, and 8 cases arising in the rectum were identified. Finally, 28 cases of infantile and adolescent leiomyosarcoma were reviewed. Although survival analysis is precluded by small case numbers and limited survival data availability, the trend identifies that increased size and mitotic activity portends to a worse prognosis in small bowel leiomyosarcomas. Colonic leiomyosarcomas appear to be aggressive tumors, regardless of tumor size and mitotic activity. Rectal leiomyosarcomas present as smaller tumors with favorable prognosis. Leiomyosarcomas in post-GIST era are rare tumors of the gastrointestinal tract with distinctive clinicopathologic characteristics. Owing to different treatment options, it is necessary to accurately differentiate these from GIST, using a combination of histologic appearance, presence of smooth muscle antigens, and absence of specific GIST immunomarkers.

Pediatric gastrointestinal stromal tumor

Pediatric gastrointestinal stromal tumor (GIST) is a rare entity that can be quite different from its adult counterpart. This report provides a comprehensive review on the diagnosis and management of this tumor in children and adolescents, including its oncogenesis and associated syndromes. Surgery remains a mainstay of treatment, but there are no standard guidelines available at this time regarding the best practice for multimodality therapy as our understanding of the biology of GIST is still in evolution. Therefore, pediatric patients with GIST should be ideally treated in the context of clinical trials at specialized, multidisciplinary centers throughout the course of their disease, especially because these patients may live for years after diagnosis.

Histopathology of gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST), generally driven by oncogenic KIT or PDGFRA mutations, is the most common mesenchymal tumor of the gastrointestinal (GI) tract. GIST is most common in the stomach (60%) and small intestine (30%), but can occur anywhere in the GI-tract and the intra-abdominal soft tissues. GIST can show spindle cell or epithelioid morphology, and mitotic count and tumor size are most important prognostic parameters. GISTs in NF1 patients and children are distinctive clinicopathologic groups. Immunohistochemical testing for KIT and sometimes for DOG1/Ano 1 is essential in confirming the diagnosis.

Morphology of gastrointestinal stromal tumors: historical perspectives

About 2/3 of gastrointestinal stromal tumors occur in the stomach and about 1/5 in the small intestine with few in the rectum, colon, and esophagus. Their cells are related to the interstitial cells of Cajal. They differ by site in terms of cell type and growth pattern. Benign and malignant tumors are separated based on their light microscopic appearances, size as measured by innumerable pathologists and assistants and mitotic counts.

Surgical treatment of gastrointestinal autonomic nerve tumors (GANT) in children-2 case reports

Gastrointestinal autonomic nerve tumors form an uncommon subcategory of stromal tumors of the intestinal tract although their histologic appearance is similar to other gastrointestinal stromal tumors. Our aim was to evaluate our experience in the diagnosis and therapy of these kinds of tumors. Two patients were admitted to the Pediatric Surgery Clinic in Niš with abdominal pain and a palpable mass in the abdomen. After excision, the tumor tissue was sampled, sent for histopathological diagnosis, and examined by light microscopy, immunohistochemistry, and electron microscopy. Postoperatively, both patients recovered without complications. The patient with the tumor bulk in the mesentery of the small bowel had no evidence of tumor progression 6 years after surgery. In the second case, a giant tumor was present along the greater curvature of gaster. Even with a tumor of this size, there were no signs of progression 10 years after surgery. Radical surgical resection of gastrointestinal autonomic nerve tumors seems to be the curative approach to date, and long-term survival is possible even with large tumors.

Small-Intestinal Rhabdoid Gastrointestinal Stromal Tumor (GIST)

Rhabdoid features in gastrointestinal stromal tumors (GISTs) are rare. To the authors’ knowledge, only 51 cases have been reported. Most of these reports consist of case series in which the rhabdoid GISTs comprise a small proportion of the tumors studied. Information regarding site of origin and clinical behavior is sparse. Although the stomach is the only site of origin documented, most reports do not include this data. Malignancy has not been reported, though follow-up is inadequate in most cases to comment on tumor behavior. Exon 11 mutations comprise all previously described KIT mutations, the majority of which are deletions. The authors present the case of a malignant small-intestinal rhabdoid GIST that recurred twice following resection and treatment with tyrosine kinase inhibitors. The tumor harbored a KIT exon 11, 579-580 LY insertion that, to the authors’ knowledge, has not been previously reported. This case is the first rhabdoid GIST described in the small intestine and is the first to show documented evidence of malignancy.

Best practices in diagnostic immunohistochemistry: spindle cell neoplasms of the gastrointestinal tract

CONTEXT

The proper classification of spindle cell neoplasms of the gastrointestinal tract frequently requires the use of immunohistochemistry, as the histologic appearance of these lesions often overlaps.

OBJECTIVE

To review the antibodies used in the diagnosis of spindle cell neoplasms of the gastrointestinal tract, and to outline an approach to the evaluation of these lesions by using immunohistochemistry.

DATA SOURCES

The authors' experience and a review of the English literature from 1976 to 2008.

CONCLUSIONS

The most common spindle cell neoplasm of the gastrointestinal tract is gastrointestinal stromal tumor; this lesion is readily diagnosed with c-kit immunohistochemistry in most cases. Other stains, such as smooth muscle actin, desmin, S100 protein, and beta-catenin, are also useful in the diagnosis of smooth muscle tumors, schwannomas, desmoid-type fibromatoses, and metastatic melanoma.

Surgery for gastrointestinal stromal tumors of the stomach

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the main mesenchymal neoplasms in the gastrointestinal tract. Tumor size, mitotic rate, and location correlate with potential malignancy and recurrence rate. Results of surgical treatment of gastric GIST are analyzed with emphasis on recurrence of disease after intermediate follow-up.

METHODS

From 1998 to 2006, a total of 63 patients (median age 62.1 +/- 14.1) underwent gastric resection for GIST. Fifty-five patients (93.6%) returned for follow-up investigations, which included computed tomography in 45, gastroscopy in 32, and endosonography in 29. Positron emission tomography was done in five patients.

RESULTS

Mean tumor size was 5.3 +/- 3.8 cm. Open atypical gastric resection was done in 32, distal gastric resection in five, and remnant gastrectomy in four patients. Laparoscopic gastric resection was initiated in 22 patients; the conversion rate was four of 22 (18.2%). Overall, R0 resection was reached in 61/63 patients (96.8%). According to the Fletcher criteria, 33 tumors (52.4%) were classified as intermediate or high risk GIST. Six patients (9.5%) died of unrelated causes before follow-up. After a median follow-up of 2.5 years, overall recurrence rate was 7.0% after R0 resection.

CONCLUSION

Histologically proven complete resection is an effective treatment for gastric GIST. Laparoscopic procedures were carried out successfully in selected patients.

An Atypical Equine Gastrointestinal Stromal Tumor

A 17-year-old, gelded Quarter Horse cross was found to have a large, intra-abdominal mass. Clinical signs included infrequent mild colic, weight loss, and chronic anemia. Surgery revealed a very large, discrete, hemorrhagic, multilobular mass with vascular attachments to the transverse colon, mesocolon, jejunal mesentery, and omentum; the site of origin was the transverse colon. Histologic examination demonstrated dense sheets, fascicles, palisades, and interconnecting streams of neoplastic spindle cells with lesser numbers of admixed multinucleated giant cells. Based on morphology alone, this neoplasm might have been misdiagnosed as a peripheral nerve sheath tumor because many of the morphologic features were suggestive of neural differentiation. Neoplastic cells expressed cluster of differentiation (CD)117 (c-kit), vimentin, desmin, smooth muscle actin, neuron-specific enolase, and S-100 protein and did not express cytokeratin. Based predominantly on the immunohistochemical profile, especially the CD117 positivity, this neoplasm was diagnosed as a gastrointestinal stromal tumor with both myogenic and neurogenic differentiation. The morphology and immunohistochemical profile of this neoplasm were different from published cases of equine gastrointestinal stromal tumors. Unusual aspects included the large size of this neoplasm, the neuroid rather than myxomatous morphology, the presence of multinucleated giant cells, and the expression of desmin.

Surgery for gastrointestinal stromal tumors of the stomach

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the main mesenchymal neoplasms in the gastrointestinal tract. Tumor size, mitotic rate, and location correlate with potential malignancy and recurrence rate. Results of surgical treatment of gastric GIST are analyzed with emphasis on recurrence of disease after intermediate follow-up.

METHODS

From 1998 to 2006, a total of 63 patients (median age 62.1 +/- 14.1) underwent gastric resection for GIST. Fifty-five patients (93.6%) returned for follow-up investigations, which included computed tomography in 45, gastroscopy in 32, and endosonography in 29. Positron emission tomography was done in five patients.

RESULTS

Mean tumor size was 5.3 +/- 3.8 cm. Open atypical gastric resection was done in 32, distal gastric resection in five, and remnant gastrectomy in four patients. Laparoscopic gastric resection was initiated in 22 patients; the conversion rate was four of 22 (18.2%). Overall, R0 resection was reached in 61/63 patients (96.8%). According to the Fletcher criteria, 33 tumors (52.4%) were classified as intermediate or high risk GIST. Six patients (9.5%) died of unrelated causes before follow-up. After a median follow-up of 2.5 years, overall recurrence rate was 7.0% after R0 resection.

CONCLUSION

Histologically proven complete resection is an effective treatment for gastric GIST. Laparoscopic procedures were carried out successfully in selected patients.

[Gastrointestinal stromal tumors. Diagnosis and estimating aggressiveness]

A diagnosis of gastrointestinal stromal tumor must be considered if a mesenchymal tumor is localized in the gastrointestinal tract, especially in the stomach. In daily practice diagnosis is based on the histology (cellular features and histologic architecture) and immunohistochemistry (cellular positivity with antibodies to CD117 and often to CD34). Expression of CD117 indicates the autoactivation of a type-III-receptor tyrosine kinase mediated by mutation of the KIT gene. This is lacking in the roughly 5% of cases which instead show a mutation of the PDGF receptor alpha gene. The estimation of dignity is difficult and can be uncertain in some cases. A malignancy grading according to the procedure in soft tissue tumors is not possible. Nowadays, however, the general consensus is that size of the tumor and number of mitoses are the most important criteria for appraising tumor aggressiveness and risk of metastasis. The tumor localization was later added to these criteria. Recent years have shown that mutation analysis can also provide information for judging tumor aggressiveness and predicting possible metastasis and response to therapy.

[Stromal tumour of duodenal autonomous nerves (plexosarcoma)]

Gastrointestinal tumours arising from autonomous nerves of Meisner's or Auerbach's plexus (plexomas and plexosarcomas) are rare tumours in only 87 cases described in the literature up to 2001. We present a very rare case of gastrointestinal stromal tumour (plexosarcoma) of the third and fourth portion of the duodenum, 130 x 98 x 87 mm in diameter, arising from its back wall, with central necrosis of the well circumscribed tumour, which communicated with the duodenum through an ulceration of 15 x 7mm in diameter, spreading towards the great vessels of the retroperitoneum. It was gradually and carefully removed, together with 17 cm of the duodenum and few centimetres of the jejunum with end-to-end duodenojejunostomy below the Vater's papilla. During the removal of the tumour, the superior mesenteric artery, being within the tumour's capsule, was accidentally ligated but not transsected. In spite of the removal of the ligature, the artery became thrombosed due to damage of the intima by ligature so that it had to be resected and reanastomosed. After otherwise uneventful recovery, except for a mild pus discharge through the drain, not far from the arterial anastomosis, the patient suddenly started bleeding on the 13th day after surgery. At emergency reoperation, a rupture of the mesenteric artery above the thrombosed anastomosis was found. In spite of absence of the arterial pulsation within the mesentery, the bowel looked vital and the back flow from the artery was satisfactory. The arterial rereconstruction was not possible, so the artery was ligated. The postoperative recovery was surprisingly uneventful. The patient was discharged ten days after surgery and has stayed symptom-free so far.

Gastrointestinal stromal tumors: differential diagnosis

Availability of KIT tyrosine kinase inhibitors for specific treatment of GISTs has magnified the importance of accurate differential diagnosis of GIST from other tumors occurring in the GI tract and abdomen. The general problems in this distinction include histological mimicry of other mesenchymal tumors with GIST, occasional KIT-negativity of GIST, and KIT-positivity of non-GISTs. Up to 5% to 10% gastric GISTs and <2% of intestinal GISTs can be KIT-negative. The identification of these tumors as GISTs is based on knowledge of the spectrum of GIST morphology, and can be supported by molecular diagnosis of KIT and PDGFRA mutations (the latter pertain to gastric tumors). True smooth muscle tumors (rare in GI tract except in esophagus and colon) can be separated from GISTs by the eosinophilic tinctorial quality of tumor cells, positivity for smooth muscle markers, and negativity for KIT. Desmoids can form large GIST-like masses, but are composed of spindled or stellate-shaped cells in a densely collagenous stroma. Negativity for KIT and nuclear positivity for beta-catenin are differentiating features. GI schwannomas, melanoma, and rare primary clear cell sarcoma are S100-positive, usually with characteristic histology. The latter two can be KIT-positive. KIT-positive non-GISTs include some sarcomas, especially angiosarcoma and Ewing sarcoma, extramedullary myeloid tumor, seminoma, and a few carcinomas, notably small cell carcinoma of lung. Spurious KIT-positivity, seen with some polyclonal KIT antibodies, has been a source of confusion leading to probable false-positive results in fibroblastic tumors and occasional other sarcomas, such as leiomyosarcomas. Integration of histological features with carefully standardized immunohistochemistry, supported by KIT and PDGFRA mutation analysis, is the cornerstone of state-of-the art differential diagnosis of GIST. To comprehensively capture all GISTs, KIT immunostains should be performed on all unclassified epithelioid and mesenchymal tumors of the abdomen. This is a US government work. There are no restrictions on its use.

Gastrointestinal stromal tumors: pathology and prognosis at different sites

Gastrointestinal (GI) stromal tumors (GISTs) are the most common mesenchymal tumors specific to the GI tract, generally defined as KIT (CD117)-positive tumors with a characteristic set of histologic features. These tumors, derived from Cajal cells or their precursors, most commonly occur at the age >50 years in the stomach (60%), jejunum and ileum (30%), duodenum (4-5%), rectum (4%), colon and appendix (1-2%), and esophagus (<1%), and rarely as apparent primary extragastrointestinal tumors in the vicinity of stomach or intestines. Their overall incidence has been estimated as 10 to 20 per million, including incidental minimal tumors. GISTs are rare in children (<1%) and almost exclusively occur in stomach. They are common in patients with neurofibromatosis 1, who have a predisposition to (multiple) small intestinal GISTs. GISTs contain a spectrum from minute indolent tumors to sarcomas at all sites of occurrence. Their gross patterns are diverse, including nodular, cystic, and diverticular tumors. External involvement of pancreas and liver can simulate primary tumor in these organs. In general, gastric tumors have a more favorable prognosis than the intestinal ones with similar parameters. Gastric GISTs < or =10 cm and < or =5 mitoses per 50 HPFs have a low risk for metastasis, whereas those with >5 per 50 HPFs and >5 cm in diameter have a high risk for metastasis. In contrast, all intestinal GISTs >5 cm independent of mitotic rate have at least moderate risk for metastases, and all >5 mitoses per 50 HPFs have a high risk for metastases. Intestinal GISTs < or =5 cm with < or =5 mitoses per 50 HPFs have a low risk for metastases. Gastric GISTs can be divided into histologic subgroups including 4 spindle cell and 4 epithelioid variants. Intestinal GISTs are a histologically more homogeneous group and often contain distinctive extracellular collagen globules, skeinoid fibers. Immunohistochemical demonstration of KIT, CD34, or protein kinase theta positivity helps to properly identify these tumors.

Comparative ultrastructural analysis and KIT/PDGFRA genotype in 125 gastrointestinal stromal tumors

GISTs are the most common mesenchymal neoplasms of the digestive tract and are thought to originate from or differentiate toward the interstitial cell of Cajal lineage. Almost all GISTs express KIT protein and the majority show activating mutations in either KIT or PDGFRA proto-oncogenes. Ultrastructurally, these tumors have been shown to have either a smooth muscle, neuronal, dual, or null phenotype. The objective of this study was to investigate the relationship between ultrastructural features and genotype in a large series of 125 histologically confirmed and CD117 positive GISTs. PCR analysis for the presence of KIT exon 9, 11, 13, and 17 and PDGFRA exon 12 and 18 mutations was performed. There were 62 (50%) tumors located in the stomach and 45 (36%) in the small bowel. Overall, KIT mutations were detected in 93 (75%) patients: 86 (69%) in exon 11, and 7 (6%) in exon 9. A PDGFRA mutation was detected in 7 (6%) cases and 25 (19%) cases had no mutation. Ultrastructurally, skeinoid fibers were seen in 55 (44%) cases and were more common in small bowel than stomach GISTs, and occurred in only in 1 of 16 patients with an ITD (KIT) exon 11 or PDGFRA mutation. Focal actin microfilaments were identified in 82 (65%) cases and did not correlate with location or mutation type. Rare neurosecretory-type granules (NS-G) were seen in 34 (27%) of cases, but were seen in most of the cells in only 5 (4%) cases. GISTs showing both NS-G and microtubules were associated with KIT exon 11 genotype and spindle cell morphology. PDGFRA mutated cases were associated with gastric location, predominantly epithelioid morphology and lacked NS-G.

Gastrointestinal stromal tumors: review on morphology, molecular pathology, prognosis, and differential diagnosis

CONTEXT

Gastrointestinal stromal tumors (GISTs) are specific, generally Kit (CD117)-positive, mesenchymal tumors of the gastrointestinal tract encompassing a majority of tumors previously considered gastrointestinal smooth muscle tumors. They are believed to originate from interstitial cells of Cajal or related stem cells.

OBJECTIVE

To review current clinicopathologically relevant information on GIST.

DATA SOURCES

Literature in Medline and authors' own experience.

CONCLUSIONS

GISTs usually occur in older adults (median age 55-60 years) and rarely in children in the second decade (<1%) throughout the gastrointestinal tract: 60% in stomach, 35% in small intestine, and less than 5% in rectum, esophagus, omentum, and mesentery; most GISTs in the latter 2 sites are metastatic. Five percent of GISTs occur in patients with neurofibromatosis type 1 syndrome (multiple small intestinal tumors) and in Carney triad (gastric epithelioid GISTs in young females). Familial GISTs occur in patients with inheritable germline Kit or platelet-derived growth factor receptor alpha (PDGFRA) mutations. Histologically GISTs vary from spindle cell tumors to epithelioid and pleomorphic tumors. Most GISTs (95%) express Kit (CD117), CD34 (70%), and heavy caldesmon (80%), whereas 25% are positive for smooth muscle actin and less than 5% for desmin. Tumor size and mitotic activity are best predictive prognostic features; small intestinal tumors behave more aggressively than gastric tumors with similar parameters. Mutually exclusive gain-of-function Kit or PDGFRA mutations occur in a majority of GISTs representing in-frame deletions, point mutations, duplications and insertions. Mutations in Kit juxtamembrane domain (exon 11) are the most common in GISTs of all sites, whereas rare Kit extracellular domain (exon 9) Ala502-Tyr503 duplication is specific for intestinal GISTs. Mutations in PDGFRA have been identified in juxtamembrane (exon 12) and tyrosine kinase domains (exons 14 and 18), nearly exclusively in gastric GISTs, mostly in epithelioid variants. Some Kit and PDGFRA mutations have a prognostic value. Kit/PDGFRA tyrosine kinase inhibitor imatinib has been successfully used in the treatment of metastatic GISTs for more than 5 years. However, primary and acquired secondary resistance linked to certain types of Kit and PDGFRA mutations is limiting long-term success necessitating the use of alternative treatments.

Interstitial cells of Cajal (ICC) and gastrointestinal stromal tumor (GIST): facts, speculations, and myths

Interstitial cells of Cajal (ICC) is a peculiar cell network composed of cells having processes described by the eminent Spanish neuroanatomist of the 19th century, S. Ramon y Cajal. ICC became a fascinating subject to many investigators and it is estimated that there are over 100 publications yearly on the subject related to ICC, in the last three years. Now it is widely accepted that ICC are pace maker cells of the gut and probable progenitor cells of gastrointestinal stromal tumors (GIST). Lately, interstitial Cajal-like cells (ICLC) are being found in various organs and their physiological role is still to be defined. We have reviewed the literature trying to evaluate the validity of the current concept and found that there are a few salient points to be considered. 1) There has been some important departure in defining the identity of ICC from the original criteria of Cajal. In particular, ICC with myoid feafures in intestinal smooth muscle layers (ICC-DPM) do not seem to fit to the original description of interstitial cell network by Cajal. We have also pointed out that the current reports assigning a pace maker role to ICC vastly depend on the scientific data on "ICC with myoid features", not on "fibroblast-like ICC", which are more abundant and easier to identify. 2) There seem to be an overwhelming amount of data proving the relationship between ICC and GIST. Both are known to express c-Kit and the ultrastructural characteristics seen in GIST roughly parallel those of ICC including minimal myoid differentiation seen in the majority of GIST, supporting the current concept that GIST are ICC tumors. 3) According to the original description of Cajal, ICC was not limited to the gut, suggesting an existence of ICC in other organs. The list of organs reported to contain ICC (currently identified by immunohistochemistry and electron microscopy) is ever growing and further studies are needed to define their identity and pathophysiologic role. 4). Recent data concerning gut development suggest that both c-Kit expressing ICC (fibroblasts-like as well as muscle-like) and gut muscle cells derive from the common progenitor cells of the embryonic gut unifying the histogenetic concept of all GIST with heterogeneous cytomorphologic features. In this review we attempted to incorporate recent information on interstitial Cajal-like cells (ICLC) found in other organs to broaden our understanding of ICC in general in terms of their ultrastructure, physiology, and neoplasia.

Gastrointestinal stromal tumours: an update

Recently, there has been intense interest in the study of gastrointestinal stromal tumour (GIST); one might call it a virtual GIST revolution. This is due largely to the realization that most GISTs express KIT and harbour activating c-KIT (KIT) or platelet-derived growth factor receptor-alpha (PDGFRA) receptor tyrosine kinase mutations that can be targeted by small molecule pharmacological inhibitors. Pathologists have benefited greatly from this revolution, mainly in the form of an improved ability to classify GISTs and, even more recently, in understanding the molecular underpinnings that underlie many fascinating clinical and pathological correlations. It is the purpose of this review to summarize recent developments in GIST classification and the molecular pathogenesis of GIST.

Polypoid pleomorphic sarcoma of the colon

In contrast to common colonic epithelial neoplasms, polypoid mesenchymal tumors of the colon are extremely rare. The majority of uncommon gastrointestinal mesenchymal tumors are associated with the so-called gastrointestinal stromal tumors (GIST). We present a case of a rare colonic pleomorphic sarcoma, macroscopically mimicking a common epithelial colonic polyp, which did not match the criteria of GIST. In this case report we discuss the clinical and pathological characteristics of a rare polypoid-shaped, pleomorphic colonic sarcoma and refer a mark-off to other rare mesenchymal neoplasms of the gut.

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 autonomic nerve tumours--report of a case and review of literature

BACKGROUND

Gastrointestinal autonomic nerve tumours are uncommon stromal tumours of the intestinal tract. They can involve any part of the gastrointestinal system, but are very rarely seen in the rectum.

CASE PRESENTATION

We report a unique case of rectal schwannoma with associated synchronous adenocarcinoma of the splenic flexure and adenoma of the descending colon. A 70-year-old patient was admitted with complaint of bleeding per rectum and investigations revealed the presence of a large submucosal rectal lesion in addition to the colonic pathologies. Following panproctocolectomy with permanent spout ileostomy, histopathology and immunohistochemistry confirmed the rectal lesion to be a schwannoma.

CONCLUSION

Literature review of the few reported cases has suggested radical surgical excision to be the best approach. Prognosis tends to be favourable after resection.

Prognostic value of KIT mutation in gastrointestinal stromal tumors

AIM: To examine the prevalence and prognostic significance of C-kit gene mutation and analysis the correlation of C-kit gene mutation and the clinicalpathologic parameters of GISTs.

METHODS: Eighty-two GISTs were studied for the mutation of C-kit gene by PCR-SSCP, DNA sequence. Statistical comparison were used to analysis the correlation of C-kit gene mutation and clinicalpathology, clinical behavior, recurrence.

RESULTS: (1) Mutation-positive and mutation-negative GISTs were 34 and 48,respectively; (2) Among these patients with C-kit mutation remained a significantly poor prognosis associated with 59% 3-year survival compared to those whose tumors did not; (3) Tumor size, PCNA index, mitotic cell number, presence of necrosis, microscopic invasion to adjacent tissues, recurrence and distant metastasis among mutation-positive and mutation-negative GISTs were significantly different.

CONCLUSION: C-kit mutation is a undoubtedly pivotal event in GIST and may be associated with poor prognosis. Evaluation of C-kit gene mutation may have both prognosis and therapeutic significances.

Gastrointestinal stromal tumours (GISTs): a clinicopathological and molecular study of 66 cases

AIMS

Predicting the clinical behaviour of gastrointestinal stromal tumours (GISTs) is difficult and criteria delineating benign from malignant cases are not firmly established. The aims of this study were to define the clinicopathological and molecular features of 66 GISTs, and to determine whether any specific parameters were associated with patient outcome.

METHODS

Archival cases of GIST from two major teaching hospitals in Western Australia were studied. Inclusion criteria for the study were: (1) appropriate morphology, (2) CD117 positivity, (3) adequacy of pathological material for study, and (4) exclusion of other tumour types on the basis of immunophenotypic and/or ultrastructural features. Expression of CD117, CD34, S100 protein, keratin (using broad spectrum MNF116), alpha-smooth muscle actin (SMA) was determined by immunohistochemistry. PCR and single strand conformation polymorphism (PCR-SSCP) analysis were used to screen for mutations in exons 11 and 9 of c-kit.

RESULTS

There were equal numbers of males and females with a mean age at diagnosis of 60 years, followed up for a mean of 54 months. Thirteen patients (21%) had died of GIST by the end of the study. Tumours were mostly located in the stomach (67%) and small intestine (SI; 25%). The cell types were pure spindle (68%), pure epithelioid (12%) and mixed epithelioid/spindle (20%). c-kit mutations were found in 69% of GISTs, with the large majority (91%) occurring in exon 11. Size > or = 10 cm, tumour necrosis and pure epithelioid cell morphology each were the only factors significantly associated with adverse survival (p=0.038, and p=0.047 and p=0.028, respectively). Mitotic activity > or = 5/50 HPF showed a definite trend association with adverse survival, but unlike some other studies, did not achieve statistical significance (p=0.067). c-kit mutations were more frequent in small intestinal GISTs (p=0.05) and in those with pure spindle cell morphology (p=0.023) but were not associated with patient outcome.

CONCLUSION

In this study, size > or = 10cm, necrosis and/or pure epithelioid cell morphology correlated significantly with adverse survival. Mitotic activity showed a strong association with survival but this did not reach statistical significance. c-kit mutations occurred mainly in GISTs of the SI, and in purely spindle cell tumours. While the mutation status did not associate with patient outcome in this series, this remains a controversial issue, and further studies are needed to assess whether the type of mutation affects response to tyrosine kinase inhibitor therapy in metastatic GISTs. CD117 staining of any mesenchymal lesion of the gastrointestinal tract should be mandatory for accurate classification. PCR-SSCP analysis is a fast, sensitive and relatively inexpensive method of analysing c-kit mutations, which may be important prognostically and also of therapeutic relevance in the assessment of new tyrosine kinase inhibitor therapies.

KIT gene deletions at the intron 10-exon 11 boundary in GI stromal tumors

Most gastrointestinal stromal tumors (GISTs) harbor oncogenic mutations in the KIT gene, and the majority of these mutations affect the juxtamembrane domain of the kinase encoded by exon 11. Screening GISTs for KIT gene mutations is important for translational research studies and for providing prognostic information on the likelihood of tumor response to treatment with the kinase inhibitor imatinib mesylate (Gleevec). In a series of GISTs analyzed in our laboratory by a combination of denaturing HPLC and direct DNA sequencing, we identified 19 cases with KIT exon 11 deletions that included from 1 to 14 bp of intron 10 sequence and resulted in loss of the normal splice acceptor site at the beginning of exon 11. Predicted use of the next potential splice-acceptor site was confirmed by cDNA sequencing in 4 cases. Thus, the resulting mutant isoform, deletion KPMYEVQWK 550-558, was the same in all 19 cases. Only two other examples of deletions across the intron 10-exon 11 boundary have been reported, yet among 722 GISTs analyzed in our laboratories these deletions were not uncommon, accounting for 3.9% of exon 11 mutations and 2.6% of all tumors. Loss of KIT intron 10 sequences may be under-recognized if the forward primer is too close to exon 11, or if cases are examined exclusively at the cDNA level. Laboratories that offer clinical screening for KIT mutations in GI stromal tumors should be aware of this class of mutations.

Gastrointestinal stromal tumors: a clinicopathologic and immunohistochemical study of 136 cases

The clinicopathologic features of 136 gastrointestinal stromal tumors were analyzed. The tumors occurred in 60 women and 76 men, ranging in age from 19 to 88 years (median 59 years, mean 59.2 years). Sixty-one cases arose from stomach, 38 from small intestine and 11 from colon or rectum. Abdominal cavity was indicated as tumor site in 10 cases, but the extra-gastrointestinal origin using strict criteria was not proved. Four locally recurrent cases and 12 metastatic samples were also included. The primary and recurrent tumors ranged in size from 0.5 to 30 cm (mean 8.3 cm). The large number of high-grade cases (85 of 112 classifiable) is alarming and emphasize the importance of oncology care. Histologically, ninety-two cases were classified as spindle cell while 11 as epithelioid GIST. Mixed cellularity was seen in 33 cases. Skeinoid fibers were present in 14 and coagulation necrosis in 40 primary cases. Ulceration observed by microscopic examination was common (36 of 110 cases, 32.7%), explaining the clinically frequently observed gastrointestinal bleeding. Unusual histological features such as stromal hyalinization and nuclear palisading were present in 30 and 27 cases, respectively. Immunohistochemical CD117 (c-kit) positivity was documented in 133 cases. Three cases with CD117 negative results were included, because their morphology was most consistent with GIST and immunohistochemical reactions excluded the possibility of other neoplasms. CD34 positivity was seen in 70%, alpha-smooth muscle actin positivity in 39.6% of examined cases. Only one case showed desmin reactivity and seven had S100 positive tumor cells. For h-caldesmon 39 cases proved to be positive (60.9% of the tested cases).

Loss of heterozygosity on chromosome 22q in gastrointestinal stromal tumors (GISTs): a study on 50 cases

Mutational activation of KIT or PDGFRA is considered an early step in pathogenesis of gastrointestinal stromal tumors (GISTs); however, other nonrandom genetic changes have also been identified. At least three common regions of deletions on chromosome 22q, which may harbor putative tumor suppressor genes, have been defined. However, mapping of these regions has been inconsistent. It has also been speculated that GI autonomous nerve tumors (GANTs), GISTs with ultrastructural features suggestive of autonomic nerve differentiation, are characterized by a specific deletion involving 22q13 cytogenetic region. This study was undertaken to evaluate loss of heterozygosity (LOH) on chromosome 22q in 50 GISTs, including 10 GANTs. Four tumors were incidental minimal lesions <or=10 mm in diameter. LOH was evaluated using 20 PCR-based microsatellite markers and capillary gel electrophoresis. In all, 15 (30%) cases showed LOH of more than 75% of informative markers, suggesting loss of chromosome 22q. A total of 24 GISTs (50%) revealed LOH of one to seven informative markers clustered in different loci suggesting simultaneous involvement of different regions. The highest frequency of LOH was seen at D22S922 and D22S425, mapped to 22q13.33 and 22q11.22, respectively. However, LOH at other regions including IL2RB and NF2 locus was also found. No NF2 mutations were identified in four analyzed tumors. LOH on chromosome 22q was more frequent among intestinal than among gastric GISTs; however, there was no difference between LOH pattern seen in tumors defined by different histologic, ultrastructural (GANT) and molecular features (KIT and PDGFRA mutations). Although minimal GISTs revealed LOH on chromosome 22q, there was a higher LOH frequency in malignant than in benign tumors. An isolated LOH at D22S425 was equally found in both benign and malignant tumors. These observations may suggest that LOHs on chromosome 22q in GISTs play a role in early stages of tumor formation as well as in late tumor progression.

Cell transformation effect of mutant c-kit gene in gastrointestinal stromal tumor

AIM: To investigate the implication in tumorigenesis of a novel c-kit gene mutant, which was identified recently in gastrointestinal stromal tumor (GIST), by examining its effect on cell proliferation and cell cycle.

METHODS: Recombinant plasmids, which contained mutant or wile-type c-kit gene, were stably transfected into human embryonic kidney (HEK) cells. The expression of c-kit protein was detected by Western blot. The proliferation and cell cycle of the transfected cells were detected by MTT colorimetic assay and flow cytometry, respectively.

RESULTS: In comparison with the cells transfected with wild-type c-kit cDNA and empty pcDNA3 vector, the proliferation of the cells transfected with mutant c-kit cDNA was increased significantly. The percentages of cells in proliferation phase (S+G2+M) were 48.34%, 48.24%, 42.03% and 42.16% in test, positive control, negative control and empty control group, respectively.

CONCLUSION: The mutant c-kit gene can promote human cell proliferation, which may play an important role in the malignant transformation of GIST.

Gastrointestinal stromal tumor of the stomach with rhabdoid phenotype: immunohistochemical, ultrastructural, and immunoelectron microscopic evaluation

A variety of neoplasms with rhabdoid differentiation have been reported in many sites. The authors describe a case of gastrointestinal stromal tumor (GIST) of the stomach that exhibited prominent rhabdoid features. Immunohistochemically, the tumor cells displayed positive staining for vimentin, c-kit, CD34, and alpha smooth muscle actin. Ultrastructural examination of the rhabdoid tumor cells revealed paranuclear whorls of intermediate filaments, which were immunoreactive for vimentin by both light microscopic immunohistochemical and protein A gold immunoelectron microscopic techniques. On H&E light microscopic examination alone, such a tumor could be mistaken for a variety of epithelial, mesenchymal, or other neoplasms that may show rhabdoid features. One report of GIST with a rhabdoid histologic phenotype has been described. This is the second known report of such a case with immunophenotypic and ultrastructural evaluation, and the first case with immunoelectron microscopic examination.