Gastrointestinal stromal tumors/smooth muscle tumors (GISTs) primary in the omentum and mesentery: clinicopathologic and immunohistochemical study of 26 cases

Improved detection of KIT exon 11 duplications in formalin-fixed, paraffin-embedded gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common gastrointestinal mesenchymal tumors driven by KIT or PDGFRA mutations. A majority of these mutations affect KIT exon 11 and represent deletions or point mutations, but insertions and duplications have also been reported. The latter have been found exclusively in the 3' part of KIT exon 11. Reported frequency of duplications varies, and a higher frequency has been reported in studies based on frozen tissue. Recently, we have hypothesized that in some cases, the duplications might remain undetected in formalin-fixed, paraffin-embedded GISTs because of the preferential polymerase chain reaction (PCR) amplification of wild-type KIT over the mutant allele. In this study, 16 GISTs initially diagnosed as a wild-type KIT were evaluated using PCR assay amplifying only the 3' part of KIT exon 11, the region commonly affected by duplications. Denaturing high-pressure liquid chromatography and direct sequencing analyses revealed duplications in 4 (25%) of 16 analyzed cases. Use of the PCR assay amplifying the specific region affected by duplications and yielding 129 bp in wild-type KIT can substantially improve the detection of these mutations in formalin-fixed, paraffin-embedded GISTs.

Vaginal tumors with histologic and immunocytochemical feature of gastrointestinal stromal tumor: two cases and review of the literature

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract (GI). Although positive immunohistochemistry for c-kit protein (CD117) and CD34 is critical in establishing diagnosis, the clinicopathologic features of CD117-positive mesenchymal tumors without obvious connection to the GI tract are not well documented. We describe the clinicopathologic features of two cases of extra-GIST. Case 1 was a 42-year-old woman who presented with a submucosal tumor located in the posterior vaginal wall. Case 2 was a 66-year-old woman who presented with a mass that bulged from the right side of the middle vaginal wall. Both tumors were excised locally. The results of microscopic examination and immunohistochemistry for both cases indicated the diagnosis of GIST. Case 2, in addition, showed oncogenic mutation in KIT exon 11. Case 1 is healthy without evidence of recurrence 4 years after surgery. Case 2 started imatinib therapy after resection of a recurrent mass. Gynecologists as well as diagnostic pathologists should be aware of GIST manifesting as a vaginal mass. Recognition of microscopic patterns and characteristic immunohistochemical phenotype, plus genetic study, is mandatory for establishing the correct diagnosis of GIST.

Primary oral KIT-positive tumour consistent with gastrointestinal stromal tumour

Gastrointestinal stromal tumours are characteristically positive for KIT (reflective of the c-KIT gene). A case is reported of an apparent rapidly growing gastrointestinal stromal tumour, which arose in the floor of the mouth and metastasized to the left neck without evidence of disease elsewhere.

Primary stromal tumor of the omentum: Report of a case

We report the case of a primary extragastrointestinal stromal tumor (EGIST) found in the omentum of a 65-year-old woman. The resected specimen, which measured 6 cm at its largest point, consisted of an outer solid part and inner uniloculated cysts. Microscopically, the tumor was characterized by interlacing bundles of elongated spindle cells, with the nuclei showing a focal palisading pattern; however, skenoid fibers were not observed anywhere and mitoses were absent. Immunohistochemically, the tumor was negative for smooth-muscle actin, desmin, and S-100 protein, but it was positive for CD117 and CD34. The microscopic features were consistent with a gastrointestinal stromal tumor.

Primary gastrointestinal stromal tumor in the retroperitoneum

Gastrointestinal stromal tumor (GIST) is the most frequent non-epithelial neoplasm in the gastrointestinal tract. GIST has received much attention both for its clinical significance and biological nature, while the retroperitoneal condition identical to GIST has been rarely described. Presented herein is a case of GIST arising from the retroperitoneum in a 67-year-old man. The solid tumor measuring 4 cm was uncovered in the retroperitoneum, between the abdominal aorta and inferior vena cava, on computed tomography. The patient underwent surgical excision of the tumor. Histological examination showed proliferating spindle cells in the clearly demarcated tumor; immunoreactivity for Kit and CD34 in tumor cells confirmed the diagnosis of GIST. The histological origin of GIST is suggested to be gastrointestinal pacemaker cells, because they share specific immunoreactivity for CD117/Kit, which is also relevant to pathogenesis of GIST. The present case was a rare primary GIST in the retroperitoneum with typical immunopathological features.

Interstitial Cajal-like cells in rat mesentery: an ultrastructural and immunohistochemical approach

Interstitial Cajal-like Cells (ICLC) were recently recognized in a plethora of non-digestive organs. Here, we describe a cell type of rat mesentery sharing ultrastructural and immunohistochemical features with ICLC. Mesenteric ICLC were demonstrated by transmission electron microscopy (TEM) and further tested by light microscope immunohistochemistry. The cell described here fulfils the TEM diagnostic criteria accepted for ICLC: location in the connective interstitium; close vicinity to nerves, capillaries and other interstitial cells; characteristic long, moniliform cell processes; specialized cell-to-cell junctions; caveolae; mitochondria at 5–10% of cytoplasmic volume; rough endoplasmic reticulum at about 1–2%; intermediate and thin filaments, microtubules; undetectable thick filaments. The processes of this mesenteric ICLC were particularly long, with a mean length of 24.91 μm (10.27–50.83 μm), and a convolution index of 2.32 (1.37–3.63) was calculated in order to measure their potential length. Mean distances versus main target cells of ICLC–nerve bundles, vessels, adipocytes and macrophages–were 110.69, 115.80, 205.07 and 34.65 nm, respectively. We also tested the expression of CD117/c-kit, CD34, vimentin, α-smooth muscle actin, nestin, NK-1, tryptase and chymase and the antigenic profile of the mesenteric ICLC was comparable if not identical with that recently observed in ICLC from other extra-digestive tissues. Due to the peculiar aspect of the mesenteric ICLC processes it can be hypothesized that these cells form a three-dimensional network within the mesentery that is at the same time resistant and deformable following stretches consequent to intestine movements, mainly avoiding blood vessels closure or controlling blood vessels rheology. It remains, however, to be established if and how such cells are connected with the archetypal enteric ICC.

Interstitial cells of Cajal in health and disease. Part II: ICC and gastrointestinal stromal tumours

Mesenchymal tumours in the gastrointestinal tract have long been problematic in terms of diagnosis, prognosis and therapy, but recent advances in immunohistochemistry and related therapies have allowed more specific diagnosis. In particular, the recognition that both the interstitial cells of Cajal (ICC) and many gastrointestinal stromal tumours (GISTs) are positive for c-kit and CD34 and have other features similar to those of ICC has led to the use of imatinib, a novel small molecule therapy that blocks the CD117/c-kit tyrosine kinase receptor, which shows remarkable efficacy in treatment of malignant and metastatic GISTs as well as other malignancies.

Glomus tumor of the omentum: A case report

Computed tomography revealed a well-enhanced omental mass. Magnetic resonance imaging demonstrated a mass with low signal intensity on T1-weighted images (WI) and high signal intensity on T2-WI. Resected specimens immunohistochemically showed positive results for alpha-smooth muscle actin, muscle-specific actin (HHF35) and vimentin, and negative results for S-100 protein, CD34, desmin, EMA, keratin, calretinin, HBME1, and c-kit. This is the first case of an omental glomus tumor reported in the English literature.

Gastrointestinal stromal tumors (GISTs) on prostate needle biopsy: A clinicopathologic study of 8 cases

Gastrointestinal stromal tumors (GISTs) are typically not included in the differential diagnosis of spindle cell tumors seen on prostate needle biopsy. However, their recognition is critical due to their unique clinical management. We report the rare phenomenon of 8 cases of GISTs diagnosed on prostate needle biopsy. The mean patient age at diagnosis was 53.6 years (range: 42 to 65 years). Tumors variably presented with rectal fullness, urinary obstructive symptoms, and abnormal digital rectal examination. Four tumors were resected. One of these cases was shown to be primary in the rectum without prostatic involvement. The second case extensively involved the prostate but its epicenter was in the rectal muscularis propria. The third case was an encapsulated mass separated by a thin fibrous capsule from the prostate. The fourth case was a perirectal mass that underwent local excision. Four lesions have not been resected. On the basis of imaging studies, one seemed to be a prostatic mass, however, additional imaging investigations showed the mass to be separate from the prostate. Three cases have not yet been studied radiographically. Tumors measured 1.0, 1.7, 5.4, 7.0, 7.4, and 8.5 cm. The sizes of 2 recently diagnosed tumors remain undetermined. Histologically, all 8 GISTs showed spindled cells with a fascicular growth pattern. Additional histologic findings included focal epithelioid features (n = 3), necrosis (n = 3), mitotic rates of >5 per 50 high-power field (n = 2), and cytologically malignant features (n = 3). CD117/c-kit was diffusely positive in all 8 cases and CD34 in 7/8 cases. In all cases studied, stains for S100, desmin, and smooth muscle actin were negative. Two patients were treated with imatinib mesylate. One underwent radical prostatectomy after reduction in tumor size after imatinib administration. Another patient was treated with imatinib for several months with complete tumor response and no residual tumor seen in a subsequent local excision. Rectal or extraintestinal GIST can result in a clinical impression of a prostatic lesion. One should consider CD117/c-kit in the immunohistochemical panel to exclude GIST before diagnosing a solitary fibrous tumor, leiomyosarcoma, or specialized prostatic stromal tumor on prostate needle biopsy.

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.

Large mesenteric gastrointestinal stromal tumor in a patient with familial adenomatous polyposis syndrome

We report a case of a 30-year-old man who presented with severe debilitation, anemia and diarrhea over two months. Colonoscopy revealed many (>100) polyps (familial adenomatous polyposis syndrome). Abdominal CT scan showed a large mass at the left upper abdomen in conjunction with the splenic flexure. Total colectomy with mesenteric mass and adjacent small bowel removal and ileoanal pouch was performed. Examination of the resected mesenteric mass showed a gastrointestinal stromal tumor (GIST) with scarce mitosis and infiltration of the adjacent small bowel. We describe for the first time in medical literature the coexistence of familial adenomatous polyposis syndrome and GIST in a 30-year-old man.

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.

True smooth muscle neoplasms of the gastrointestinal tract: morphological spectrum and classification in a series of 85 cases from a single institute

BACKGROUND AND AIM

True smooth-muscle neoplasms of the GI tract have been only rarely studied in the KIT era. Their incidence among other GI mesenchymal tumours and their clinicopathological spectrum have not been sufficiently analysed.

MATERIALS AND METHODS

We reviewed all GI mesenchymal lesions at the Pathology Institute of the Nuremberg Clinic Centre from 1994 through 2005.

RESULTS

Among 262 lesions, there were 142 GISTs (54%) and 85 true smooth muscle neoplasms (32%). Smooth muscle neoplasms comprised 72 polypoid leiomyomas (78%, 5 oesophageal and 67 colorectal), 10 intramural leiomyomas (11%, 5 oesophageal, 4 gastric and one ileal), two intramural leiomyosarcomas in the sigmoid colon and ileum (2%) and one polypoid leiomyosarcoma involving the stomach, descending colon and the retroperitoneum concurrently. None of the leiomyomas with available follow-up have recurred or metastasised.

CONCLUSION

Smooth muscle neoplasms are the second most common mesenchymal neoplasms in the GI tract after GISTs. They may arise either from the muscularis mucosae or proper muscle layer forming polypoid and intramural lesions, respectively. Polypoid leiomyomas are more common in the rectosigmoid, while intramural ones mainly arise in the vicinity of the oesophagogastric junction. Polypoid leiomyomas are sufficiently treated by endoscopic resection, and local surgical excision is the treatment of choice for intramural leiomyomas. Intramural leiomyosarcomas are rare high-grade sarcomas that commonly have infiltrated into the surrounding tissue or metastasised by the time of diagnosis.

[Gastrointestinal stromal tumors: definition, histological, immunohistochemical, and molecular features, and diagnostic strategy]

Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal tumors of the gastrointestinal tract. Major advances in their definition and classification and the understanding of their molecular mechanisms have recently been made. These advances have resulted in the delineation of a treatment that has become a model of targeted therapy in oncology. GISTs are defined as tumors of the gastrointestinal tract, but also of the mesentery and peritoneum, constituted by a proliferation of usually spindle-shaped, rarely epithelioid cells, usually, but not consistently expressing the KIT protein. Most GISTs are associated with molecular abnormalities in two target genes: KIT (which encodes the KIT protein) and PDGFRA (which encodes the A chain of the PDGF receptor). The diagnosis of GIST relies on histological arguments (proliferation of spindle-shaped cells in 70% of cases, of epithelioid cells in 20%; histological variants are rare and sometimes misleading) and on immunohistochemical arguments (expression of KIT in 95%, usually associated with CD34 expression in 60%-70% of cases). The demonstration of mutations in target genes is required only in cases that are histologically suggestive but KIT-negative; beyond this indication, this is only undertaken in research protocols. The differential diagnosis of GIST includes the other mesenchymal tumors of the gastrointestinal tract, such as leiomyomas and leiomyosarcomas, and the digestive locations of some sarcomas; it relies on both histological and immunohistochemical arguments. The evaluation of the prognosis is essential. According to the current concept, every GIST carries a risk of malignancy, which may vary from very low to very high. Prognosis is based on a simple algorithm using two histoprognostic parameters, i.e., tumor size and mitotic index. The treatment of localized GIST is surgical resection, which must be complete; that of advanced or unresectable GIST is based on the use of a targeted therapy, imatinib, which is a pharmacological antagonist of the KIT protein. Proper understanding and utilisation of the diagnostic criteria and classification of GIST by pathologists are essential for good patient management.

GIST: Particular aspects related to cell cultures, xenografts, and cytogenetics

In less than half a decade, gastrointestinal stromal tumors (GIST) have emerged from historical anonymity to become a model of kinase-targeted therapies. Approximately 80% to 85% of GISTs harbor activating mutations of the KIT or PDGFRA tyrosine kinase genes, and such mutations have predictive and prognostic value. In this regard, the in vitro and in vivo models have provided valuable tools for understanding the molecular pathology of this interesting neoplasm. This review charts particular aspects in the field of cell cultures and tumor xenografts in nude mice in GIST and their implication in the establishment of appropriate models for discovering and testing therapy. The cytogenetic features of these tumors are also discussed. Classic karyotyping, loss of heterozygosity, fluorescent in situ hybridization, comparative genomic hybridization (CGH), and CGH-array analyses have shown that chromosomal numerical abnormalities and loss of genetic material at chromosomes 1p, 9p, 14q, and 22q are significantly associated with GIST malignancy and response to treatment. Furthermore, these regions constitute "hot" areas for finding candidate genes involved in the pathogenesis of GISTs. A deeper knowledge of these genetic aspects of GIST will provide a better understanding of this neoplasm that could translate into clinical practice.

Fine needle aspiration biopsy of gastrointestinal stromal tumor presenting as an umbilical mass (Sister Mary Joseph's Nodule)

The Sister Mary Joseph (SMJ) nodule is a clinical sign of metastatic cancer involving the umbilicus. The vast majority of these instances represent adenocarcinomas arising from ovarian or colorectal primaries. We present a patient who presented with ascites and the SMJ lesion that turned out to be a metastatic gastrointestinal stromal tumor after fine needle aspiration biopsy was performed. The lesion was subsequently histologically confirmed. Gastrointestinal stroma tumor involving the umbilicus is exceedingly uncommon and only rarely presents in this fashion. The cytomorphological features, differential diagnosis, and comparison with the tissue specimen are made.

From the archives of the AFIP: benign fibrous tumors and tumorlike lesions of the mesentery: radiologic-pathologic correlation

Mesenteric fibromatosis, sclerosing mesenteritis, inflammatory pseudotumor, and extrapleural solitary fibrous tumor constitute a loosely associated group of benign fibrous tumors and tumorlike lesions of the mesentery. These lesions are linked histologically by the presence of fibroblasts or fibrosis and anatomically by their location within the mesentery. Although rare, and distinctly different in pathogenesis and biologic behavior, these fibrous lesions have pathologic and radiologic features that overlap with one another and with more common neoplastic and nonneoplastic lesions of the mesentery. Mesenteric fibromatosis is a locally aggressive, benign proliferative process that may occur sporadically or in association with familial adenomatous polyposis. It most frequently manifests as a focal mesenteric mass and may simulate lymphoma, metastatic disease, or a soft-tissue sarcoma. Sclerosing mesenteritis is a rare idiopathic disorder that most commonly produces a stellate mass within the mesentery and should be differentiated from metastatic disease, specifically metastatic carcinoid, because it frequently responds to conservative or medical management. Inflammatory pseudotumor (inflammatory myofibroblastic tumor) is a benign, chronic inflammatory disorder of unknown cause that manifests as a solid mesenteric mass, indistinguishable from malignancy. Extrapleural solitary fibrous tumor is a tumor of submesothelial origin that is identical to the solitary fibrous tumor of the pleura. When located in the mesentery or peritoneal cavity, extrapleural solitary fibrous tumor has an imaging pattern that must be differentiated from metastatic disease, soft-tissue sarcomas, and other benign and malignant neoplasms of the mesentery and peritoneum. Knowledge of this group of benign fibrous tumors and tumorlike lesions of the mesentery is important in the preoperative evaluation of a mesenteric mass.

Gastrointestinal stromal tumours: a regular origin in the muscularis propria, but an extremely diverse gross presentation. A review of 200 cases to critically re-evaluate the concept of so-called extra-gastrointestinal stromal tumours

BACKGROUND

Gastrointestinal stromal tumours (GISTs) are thought to arise from the interstitial cells of Cajal (ICCs). ICCs form a network surrounding the myenteric plexus and between-muscle fibres of the muscularis propria of the tubular GI tract. The cell of origin of so-called extra-gastrointestinal stromal tumours (EGISTs) is not known.

AIM AND METHODS

To study the diversity of gross presentation of GISTs and to critically assess the incidence of EGISTs and their relationship to mural GISTs, a total of 200 neoplasms with typical morphologic and immunohistochemical features of GISTs were reviewed, looking for any degree of association with the muscularis propria of the gut wall.

RESULTS

There were 130 gastric (65%), 9 duodenal (4.5%), 48 small intestinal (24%), 9 colorectal (4.5%), 1 appendiceal (0.5%) and 3 unclassifiable GISTs (1.5%). Fourteen cases (7%) were initially submitted as EGISTs (four mesenteric, four omental, one pararectal/prostatic, one pelvic/Douglas, one perivesical, one located between root of mesentery and tail of pancreas, one involving the mesentery, omentum and abdominal wall extensively and one located between liver and stomach). After critical re-evaluation of surgical reports and remote clinical history and a careful search for residual muscular tissue from the gut wall in the tumour pseudocapsule (in some cases supported by desmin immunoreactivity), it was possible to reclassify most of these cases (11/14) as either GISTs with extensive extramural growth resulting in loss of contact to the external muscle coat of the gut (8/14) or as metastases from an inoperable GIST (2/14) or from a previously resected deceptively benign tumour (1/14).

CONCLUSION

EGISTs are probably rarer than previously reported (1.5% or less in this study). We concluded that most so-called EGISTs represent apparent EGISTs that should have arisen from the outermost muscle coat, but have lost their contact to the point of origin due to extensive extramural growth pattern. From a surgical point of view, it is crucial to document and mark any focal attachment or adhesions to the gut wall noticed during surgery for an apparent EGIST. In contrast to most other neoplasms, GISTs should be defined by virtue of any degree of association with the muscularis propria (no matter how minimal), but not by localisation of the bulk of the tumour.

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.

The radiology of gastrointestinal stromal tumours (GIST)

Gastrointestinal stromal tumours (GISTs) comprise a group of smooth muscle mesenchymal alimentary tract tumours of variable malignancy. Recently, the pathophysiology and radiology of these tumours has generated enormous interest following the discovery of a specific, highly effective, chemotherapeutic agent in the form of ST-571 (Imatinib; Glivec, Novartis, Frimley UK). At the time of this review, 106 patients with malignant gastrointestinal stromal tumours seen at the Royal Marsden Hospital have been entered into trials examining the efficacy of varying doses of Imatinib. Burkill et al., also from the Royal Marsden Hospital, have previously reported the distribution, imaging features and pattern of metastatic spread of these tumours (Burkill GJ, Badran M, Al-Muderis O et al. Malignant gastrointestinal stromal tumor: distribution, imaging features, and pattern of metastatic spread. Radiology 2003; 226: 527-32). This new review re-examines the radiological features of GISTs at presentation and well as their changed imaging features following treatment with Imatinib.

Imaging gastrointestinal stromal tumors

BACKGROUND

Because of the recent reclassification of mesenchymal tumors, which was based on a better understanding of the genetics and immunophenotype of gastrointestinal stromal tumors (GISTs), only a limited number of studies have described the radiologic appearance of GISTs.

METHODS

This study reviews the imaging characteristics of GISTs, with an emphasis on differentiating benign and malignant tumors using positron emission tomography (PET), computed tomography (CT), and magnetic resonance imaging (MRI). We reviewed the data from 53 cases of GISTs treated at our institute. The imaging studies from these cases, which were recorded at our institute from January 1998 through June 2003, included PET, CT, and MRI.

RESULTS

Of the 53 GIST cases, stomach and small bowel tumors accounted for 80% of the tumors. Malignant lesions were larger and more heterogeneous, had ulcerations, and were PET positive. Peritoneal and liver metastases were most common.

CONCLUSIONS

PET, CT, and MRI appear to be useful in differentiating nonmetastasizing from malignant GISTs.

Update on the biology and therapy of gastrointestinal stromal tumors

BACKGROUND

Gastrointestinal stromal tumors (GISTs), the most common mesenchymal tumors of the gastrointestinal tract, are an example of a disease with an effective, molecularly targeted therapy.

METHODS

Published articles and author experience were used to comprehensively define the clinical features, biology, and state-of-the-art therapy of GISTs.

RESULTS

GISTs are thought to originate from the neoplastic transformation of the interstitial cells of Cajal, the intestinal pacemaker cells. GISTs commonly have mutations in the kit gene, resulting in a gain-of-function mutation and ligand-independent constitutive activation of the KIT receptor tyrosine kinase. Successful tyrosine kinase inhibitors target the aberrant pathways that are critical for tumor cell viability. The development of imatinib mesylate (formerly STI 571) in the treatment of metastatic GISTs represents a therapeutic breakthrough.

CONCLUSIONS

Progress in the clinical diagnosis has led to an increased recognition of this disease as a distinct clinical entity. Treatment of metastatic GIST with imatinib has led to unprecedented improvements in progression-free and overall survival. The use of imatinib in the preoperative and postoperative treatment of GISTs is an area of intense investigation.

[Extragastrointestinal stromal tumors: a report of 4 cases]

Gastrointestinal stromal tumors (GIST) are mesenchymal tumors that arise from the wall of the gastrointestinal tract expressing CD117 and/or the CD34. Similar tumors were described in the soft tissue of the abdomen and are so-called extragastrointestinal stromal tumors (EGIST). We report 4 new cases of EGIST. The tumors occurred in 2 women and 2 men, who ranged in age from 42 to 71 years. Three tumors arose from the soft tissue of the abdominal cavity, and the remainder arose from the retroperitoneum. They ranged in size from 10 to 27 cm. Three cases were composed purely of short fusiform cells tumors, the last case showed an epithelioid pattern. All the tumors expressed CD117. One patient presented with local recurrence and metastasis, one was lost to the follow-up and two patients were doing well. Immunohistochemistry is useful in distinguishing EGIST from other mesenchymal tumors. Intra-abdominal aggressive fibromatosis may express actin and CD117 but catenin is also positive, leiomyosarcoma expresses the actin and/or desmin but CD117 is usually negative, retroperitoneal dedifferentiated liposarcoma is CD117 negative and PS100 positive, inflammatory myofibroblastic tumor is negative for CD117 and CD34. The solitary fibrous tumor expresses CD34 and is negative to CD117. Some tumors expressing CD117 such desmoplastic round cell tumor should not be confused with EGIST. On the occasion of these four observations, we will discuss the clinical aspects and the main differential diagnoses of this tumor.

Changing phenotype of gastrointestinal stromal tumours under imatinib mesylate treatment: a potential diagnostic pitfall

AIMS

The diagnosis of gastrointesinal stromal tumours (GISTs) is widely based on morphological features and KIT (CD117) immunoreactivity. Most patients with advanced GISTs show a major clinical response after treatment with imatinib mesylate. The histopathological features of GISTs in patients on prolonged imatinib treatment have, thus far, not been addressed in detail. In this report, we present three patients with metastatic GISTs, who received more than 1 year of therapy with imatinib, and whose tumours changed their morphological and immunohistochemical characteristics during continued treatment with the drug.

METHODS AND RESULTS

All three primary GISTs from these patients were classical spindle-type tumours, showing diffuse, strong CD117, CD34, and focal alpha-smooth muscle actin expression. During treatment, two clinically progressive and one clinically stable GIST revealed a diffuse epithelioid, or pseudopapillary epithelioid growth pattern, characterized by rounded cells with eosinophilic cytoplasm and uniform round-to-ovoid nuclei. In addition, GIST specimens from patients on therapy showed complete loss of CD117 immunoreactivity. Remarkably, two of these tumours also became CD34 immunonegative and in one case the progression was accompanied by desmin expression. KIT mutational analysis revealed the presence of distinct exon 11 mutant isoforms in all cases examined, while the same genotype was sustained in the base line and on-therapy tumour specimens, proving the common origin of analysed specimens.

CONCLUSIONS

GISTs subject to imatinib treatment can undergo striking (immuno)phenotypic changes, which are not necessarily corroborated by new genotypic modifications. Because these may mimic other tumour types, this feature creates a differential diagnostic challenge, of which the pathologist should be aware.

A recurrent duodenal gastrointestinal stromal tumor with a frameshift mutation resulting in a stop codon in KIT exon 13

Gastrointestinal stromal tumors (GISTs) are a specific and rare subset of human gastrointestinal tract tumors. Most GISTs show gain-of-function mutations of KIT, mainly in exon 11, that always maintain the reading frame. We report on data from a 43-year-old Japanese man with recurrent duodenal GIST and a frameshift mutation in KIT exon 13 together with an in-frame deletion in KIT exon 11 detected by genomic DNA sequencing. Deletion of 48 base pairs of KIT exon 11, which preserved the reading frame, was identified in both primary and recurrent tumors, whereas deletion of one nucleotide of codon 642 of KIT exon 13, which changed the reading frame and induced a novel stop codon at amino acid 644, was found only in the recurrent tumor. The predicted protein resulting from the latter would lack part of the kinase domain. To the best of our knowledge, this is the first documentation of a GIST with a frameshift mutation of KIT.

Hypoxia-inducible factor-1alpha is associated with risk of aggressive behavior and tumor angiogenesis in gastrointestinal stromal tumor

BACKGROUND

The objective of this study was to evaluate the relationship of HIF-1alpha expression and tumor angiogenesis, recurrence/distant metastasis, and its value in the prediction of aggressive behavior of gastrointestinal stromal tumor (GIST).

METHODS

Paraffin-embedded specimens from 62 patients with GIST were divided into two groups, low risk (n = 31) and high risk (n = 31) according to the tumor size, mitotic count and proliferating cell nuclear antigen (PCNA) index. We investigated the expression of the HIF-1alpha and analyzed correlation with tumor angiogenesis monitored by expression of vascular endothelial growth factor (VEGF) and tumor microvessel density using immunohistochemical staining. The data were analyzed with chi(2) test or Fisher's exact test and multivariate test.

RESULTS

There were statistically significant differences between high risk (29/31; 93.5%) and low risk (8/31; 25.8%) of GIST in high expression of HIF-1alpha (P<0.0001). In addition, the incidence of recurrence/distant metastasis was significantly higher in cases of high HIF-1alpha expression (12/35; 34.3%) than in cases of low HIF-1alpha expression (1/24; 4.2%)(P = 0.009). Moreover, high VEGF expression (37/43; 86.0%) and microvessel density (30/32; 93.8%) were significantly higher in high HIF-1alpha expression tumors than in low-expression tumors (P < 0.0001).

CONCLUSIONS

Our findings suggest that HIF-1alpha may play an important role in aggressive behavior and tumor angiogenesis in GIST. In addition, high expression of HIF-1alpha was significantly correlated with tumor recurrence/distant metastasis, so it may provide an ancillary prognostic factor for GIST.

Gastrointestinal stromal tumors: clinical profile, pathogenesis, treatment strategies and prognosis

Abstract Gastrointestinal stromal tumors (GIST), although the most common mesenchymal neoplasms of the gastrointestinal (GI) tract, account for <1% of all GI malignancies. Up to 94% of these tumors express the CD117 antigen. Most patients present in the fifth to seventh decade, the commonest symptom being that of an abdominal mass. Surgery is the main modality of therapy, but even after adequate resection the vast majority of GIST reoccur, and in approximately 50% the liver is the main site of the metastasis. Long-term, maybe even lifelong follow up of these patients after initial resection cannot be over-emphasized. Initial tumor size and mitotic rate are the most useful parameters to predict malignant potential. In view of high postoperative recurrence, adjuvant forms of therapy are being explored, and the tyrosine kinase inhibitor imatinib holds the most promise.

Gastrointestinal stromal tumor presenting as a recurrent vaginal mass

Gastrointestinal stromal tumors are CD117 (c-Kit)-positive mesenchymal neoplasms with histologic and ultrastructural features of the interstitial cell of Cajal. While tumors outside of the gastrointestinal tract have been described, to our knowledge the case we present is the first such case in the vagina. We describe a 75-year-old woman with a recurrent vaginal gastrointestinal stromal tumor without apparent rectal involvement. This tumor was characterized by short intersecting fascicles of spindled cells, focal necrosis, and 12 to 15 mitoses per 50 high-power fields. Immunohistochemistry revealed diffuse cytoplasmic positivity for CD117 (c-Kit), CD34, vimentin, and h-caldesmon. Tumor cells were negative for S100, desmin, actin, and CAM 5.2. The differential diagnosis in this case included a vaginal smooth muscle tumor. While histologically similar to a smooth muscle neoplasm, the immunohistochemical profile ruled out smooth muscle differentiation. Gastrointestinal stromal tumor should be considered in the differential diagnosis of vaginal mesenchymal neoplasms.

Combination treatment of rituximab and imatinib mesylate for simultaneous relapse of MALT lymphoma and a gastrointestinal stromal tumor

A clinical case of patient with a simultaneous gastrointestinal stromal tumors (GIST) and MALT lymphoma in relapse is presented. Simultaneous treatment with imatinib mesylate and rituximab was given, yielded response for both tumors and was well tolerated.

Hypoxia-inducible Factor-1α is Associated with Risk of Aggressive Behavior and Tumor Angiogenesis in Gastrointestinal Stromal Tumor

BACKGROUND

The objective of this study was to evaluate the relationship of HIF-1alpha expression and tumor angiogenesis, recurrence/distant metastasis, and its value in the prediction of aggressive behavior of gastrointestinal stromal tumor (GIST).

METHODS

Paraffin-embedded specimens from 62 patients with GIST were divided into two groups, low risk (n = 31) and high risk (n = 31) according to the tumor size, mitotic count and proliferating cell nuclear antigen (PCNA) index. We investigated the expression of the HIF-1alpha and analyzed correlation with tumor angiogenesis monitored by expression of vascular endothelial growth factor (VEGF) and tumor microvessel density using immunohistochemical staining. The data were analyzed with chi(2) test or Fisher's exact test and multivariate test.

RESULTS

There were statistically significant differences between high risk (29/31; 93.5%) and low risk (8/31; 25.8%) of GIST in high expression of HIF-1alpha (P<0.0001). In addition, the incidence of recurrence/distant metastasis was significantly higher in cases of high HIF-1alpha expression (12/35; 34.3%) than in cases of low HIF-1alpha expression (1/24; 4.2%)(P = 0.009). Moreover, high VEGF expression (37/43; 86.0%) and microvessel density (30/32; 93.8%) were significantly higher in high HIF-1alpha expression tumors than in low-expression tumors (P < 0.0001).

CONCLUSIONS

Our findings suggest that HIF-1alpha may play an important role in aggressive behavior and tumor angiogenesis in GIST. In addition, high expression of HIF-1alpha was significantly correlated with tumor recurrence/distant metastasis, so it may provide an ancillary prognostic factor for GIST.

Reactive nodular fibrous pseudotumors of the gastrointestinal tract: report of 8 cases

Eight cases of reactive nodular fibrous pseudotumor of the gastrointestinal tract are presented. The patients included 6 males and 2 females between the ages of 1 and 68 years (mean age 41.5 years). Three tumors involved the small intestine, and 5 of the investigated lesions were located in the large bowel. Of these, 2 originated in the sigmoid colon, 1 in the cecum, 1 in the appendix, and 1 in the large bowel not otherwise specified. The tumors' size varied from 3 to 10 cm in the greatest diameter (mean 6.2 cm). Histologically they were composed of stellate or spindle shaped cells resembling fibroblasts arranged haphazardly or in intersecting fascicles, embedded in a collagen-rich stroma, with sparse intralesional mononuclear cells frequently arranged in lymphoid aggregates. Immunohistochemically, the lesions were positive for vimentin (7/7), smooth muscle actin (8/8), muscle-specific actin (5/7), cytokeratins AE1/AE3 (6/7), and CAM 5.2 (1/7), and antigen CD68 (1/7). No case (0/8) reacted positively with antibody to CD117 (c-kit). Genetically no substitutions, deletions, or insertions occurred in exon 11 in all analyzed samples. Likewise, no deletions or insertions in part of exon 9 were observed. Ultrastructurally the tumor cells revealed features typical of myofibroblasts. According to the morphologic, immunohistochemical, and ultrastructural features mentioned above, especially to the positivity of low-molecular-weight cytokeratins, we propose this lesion to be related to a proliferation of multipotential subserosal cells rather than ordinary myofibroblasts or fibroblasts.

Primitive mesenteric gastrointestinal stromal tumor with autonomic nerve/ganglionic differentiation presenting as a huge mass with small synchronous nodules

We present a case of a primary mesenteric ectopic gastrointestinal stromal tumor. The pathologic characteristics of this neoplasm, autonomic nerve/ganglionic differentiation and presentation as a huge mass with small synchronous nodules, have not been previously described in the literature.

Gastric GI stromal tumors (GISTs): The role of surgery in the era of targeted therapy

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasm arising in the stomach. These tumors were previously classified as smooth muscle tumors, but in recent years it has become clear that they are clinically, pathologically, and molecularly distinct from other tumors and are much more common than previously appreciated. Historically, patients with primary localized or advanced GIST have been managed surgically, as there was no proven role of other treatment modalities such as radiation or chemotherapy. However, the field of GIST was revolutionized with the 1998 discovery that the vast majority of these tumors have oncogenic gain-of-function mutations of the KIT receptor tyrosine kinase. Follow-up studies have confirmed that KIT is both a useful diagnostic marker and an excellent therapeutic target. Imatinib, an inhibitor of KIT kinase activity, is now the standard front-line therapy for patients with advanced GIST. In this review, we discuss pathological and molecular features of gastric GISTs and review the historic and current roles of surgery in the treatment of patients with primary or metastatic GIST. The importance of a multi-disciplinary approach using both surgery and imatinib therapy is emphasized.

Computed Tomography Imaging of Gastrointestinal Stromal Tumors With Pathology Correlation

Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors that typically arise in association with the muscularis propria of gastrointestinal (GI) tract wall. They occur most frequently in the stomach (60%) but also can occur in the small bowel (30%) or elsewhere, including the colon and rectum (5%) and esophagus (<5%). In addition, a GIST may occur as a primary tumor of the omentum, mesentery, or retroperitoneum. They account for 1%-3% of gastric neoplasms, 20% of small bowel tumors, and 0.2%-1% of colorectal tumors. These tumors arise pathologically from the wall of the GI tract and can be characterized as benign, borderline, or with low or high malignant potential based on the pathologic appearance. Computed tomography (CT) plays an important role for the diagnosis and staging of these neoplasms because it can identify the tumor and assess for local spread or distant metastases. This article reviews the role of CT in the detection and characterization of GISTs. The optimal CT technique for visualization of small bowel tumors is reviewed, and a variety of GISTs are illustrated. Pathologic correlation is also included.

[Gastrointestinal stromal tumor of the abdominal wall. An unusual localization of a rare tumor]

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. We describe here for the first time a patient with a huge GIST of the abdominal wall without any relation to the gastrointestinal tract, omentum, or mesentery. With regard to the size of 24 cm and a low mitotic index, this GIST is considered an intermediate risk for metastasis. Radical surgical resection was performed with negative pathologic resection margins. The classic immunohistochemical phenotype of the tumor described facilitates the differential diagnosis to exclude abdominal desmoid tumor and solitary fibrous tumor (SFT). In the case of metastasis, therapeutic nihilism no longer seems justified with the availability of imatinib, a tyrosine kinase inhibitor, which shows encouraging results in the therapy of metastatic GIST.

Intra-abdominal synovial sarcoma: a clinicopathological study

AIMS

To evaluate a series of synovial sarcomas arising in the abdomen, pelvic cavity, or retroperitoneum. Synovial sarcoma is rare within the abdomen. In this location, it can be confused with other biphasic tumours and with other spindle and round cell sarcomas.

METHODS AND RESULTS

Cases were retrieved from archives. There were 11 intra-abdominal tumours among 300 synovial sarcomas in two referral practices (3.7%). Three were pelvic (two midline, one sidewall) and eight were retroperitoneal. They occurred in six males and five females aged from 25 to 75 years (mean 49 years, median 46 years), and ranged in diameter from 65 to 470 mm (mean 210 mm, median 150 mm). Six examples were biphasic, five were monophasic and seven had poorly differentiated areas. Monophasic tumours displayed at least one epithelial marker. One biphasic tumour had a SYT-SSX2 fusion gene. Seven sarcomas were high-grade and four of intermediate grade malignancy. Follow-up data were available in 10 patients. In all but one case, tumour recurred or metastasized within the abdomen. The pelvic sarcomas also metastasized outside the abdomen. Eight of 10 patients (80%) died of disease with survival from 4 to 36 months (mean 17 months, median 18 months). Two patients were alive with disease at 43 and 48 months.

CONCLUSIONS

Synovial sarcomas rarely arise within the abdomen and pelvis. They occur mainly in middle age, attain a large size, are difficult to excise and recur locally. Pelvic tumours metastasize distantly. Retroperitoneal tumours remain confined to the abdomen and, unlike synovial sarcomas elsewhere, do not metastasize remotely, although mortality is high.

Gastrointestinal stromal tumor: Computed tomographic features

AIM

Gastrointestinal stromal tumor (GIST) is a rare type of cancer. Computed tomography (CT) is an imaging modality of choice for diagnosing GIST. The aim of this retrospective study was to review the CT imaging features of 17 GIST patients.

METHODS

From 1995 to 2003, there were 47 patients with pathologically proven GISTs at our hospital. Of these, 17 patients underwent preoperative CT. We collected and analyzed these CT images. The CT imaging features included tumor diameter, number and location, tumor margin, location of metastasis, hounsfield units of tumor and effect of contrasts. In addition, we also recorded the surgical findings, including complications, tumor size and location for comparative analysis.

RESULTS

The results showed that 12 (70%) tumors were located in the stomach and five (30%) were located in the jejunum mesentery. GISTs were extraluminal in 12 (70%) patients. The tumor margins of 13 (76%) tumors were well defined and irregular in four (24%). The effect of contrast enhancement on GIST CT imaging was homogenous enhancement in 13 (76%) and heterogeneous enhancement in four (24%). The hounsfield units (HU) were 30.41 +/-5.01 for precontrast images and postcontrast hounsfield units were 51.80 +/- 9.24.

CONCLUSION

The stomach was the commonest site of GIST occurrence among our patients. The CT features of GIST were well-defined tumor margins, homogenous enhancement on postcontrast CT images.

Gastrointestinal stromal tumor: Computed tomographic features

AIM: Gastrointestinal stromal tumor (GIST) is a rare type of cancer. Computed tomography (CT) is an imaging modality of choice for diagnosing GIST. The aim of this retrospective study was to review the CT imaging features of 17 GIST patients.

METHODS: From 1995 to 2003, there were 47 patients with pathologically proven GISTs at our hospital. Of these, 17 patients underwent preoperative CT. We collected and analyzed these CT images. The CT imaging features included tumor diameter, number and location, tumor margin, location of metastasis, hounsfield units of tumor and effect of contrasts. In addition, we also recorded the surgical findings, including complications, tumor size and location for comparative analysis.

RESULTS: The results showed that 12 (70%) tumors were located in the stomach and five (30%) were located in the jejunum mesentery. GISTs were extraluminal in 12 (70%) patients. The tumor margins of 13 (76%) tumors were well defined and irregular in four (24%). The effect of contrast enhancement on GIST CT imaging was homogenous enhancement in 13 (76%) and heterogeneous enhancement in four (24%). The hounsfield units (HU) were 30.41 ± 5.01 for precontrast images and postcontrast hounsfield units were 51.80 ± 9.24.

CONCLUSION: The stomach was the commonest site of GIST occurrence among our patients. The CT features of GIST were well-defined tumor margins, homogenous enhancement on postcontrast CT images.