Gastrointestinal stromal tumours: an immunohistochemical study of 165 cases

PET/Computed Tomography in the Diagnosis and Staging of Gastric Cancers

Although there has been a reduction of the incidence and mortality of gastric cancer, it remains among the commonest causes of cancer-related death. Accurate staging and evaluation of treatment response are vital for management. PET is used to complement anatomic imaging in cancer management. PET/computed tomography (CT) has demonstrated its potential value for preoperative staging, evaluation of response to therapy, and detection of recurrence. Not all types of gastric cancers have a high affinity for fluorodeoxyglucose. PET/CT in the evaluation and staging of gastric cancer is not established, but studies indicate that there may be an evolving role for this imaging modality.

F-FDG PET Imaging in the Evaluation of Treatment Response to New Chemotherapies beyond Imatinib for Patients with Gastrointestinal Stromal Tumors

Aim. (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) is a powerful tool for staging and defining "good responders" to chemotherapy in tumor setting. Gastrointestinal stromal tumors (GISTs) are sarcoma involving gastrointestinal tract and may require a chemotherapy including imatinib, a tyrosine kinase inhibitor agent. Some GIST patients become refractory to imatinib; therefore, other tyrosine kinase inhibitors or concomitant chemotherapy may be considered for treatment. The aim of this paper is to assess if (18)F-FDG PET imaging is a useful tool to evaluate treatment response to new chemotherapies beyond imatinib for GIST patients. Methods. We performed a review of the literature about the role of (18)F-FDG PET in the evaluation of treatment response to new chemotherapies beyond imatinib for GIST patients. Results and Conclusions. (18)F-FDG PET seems to be able to assess therapy response earlier than computed tomography (CT) imaging in imatinib refractory GIST patients treated with other agents. However, a dual modality PET-CT imaging is recommendable to achieve a better detection of all lesions.

Gastrointestinal stromal tumours: an update

Purpose. To study the evolution of concepts concerning gastrointestinal stromal tumours (GISTs) over 30 years.Discussion. GISTs have been, for more than 30 years, the subject of considerable controversy regarding their line of differentiation as well as the prediction of their behaviour. Furthermore, once they spread within the peritoneal cavity, they are extremely hard to control. The recent findings of c-Kit mutations and the immunohistochemical detection of the product of this gene, KIT or CD117, in the mainly non-myogenic subset of this family of tumours, has led to a reappraisal of this group of lesions, which, with some exceptions, is now thought to be derived from the interstitial cells of Cajal, and this has facilitated a clearer definition of their pathological spectrum. In this article, we review chronologically the evolution of the concept of GIST with the gradual application of electron microscopy, immunohistochemistry, DNA ploidy analysis. We discuss the impact of these techniques on the pathological assessment and clinical management of GISTs.

Management of resectable gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST) is a rare neoplasm that recently has become an intense focus of scientific investigation, as it serves as a model for the molecular therapy for cancer. Although surgery remains the principle treatment of primary localized GIST, imatinib mesylate, a selective inhibitor of KIT protein, achieves dramatic responses in metastatic GIST. Multimodality therapy integrating surgery and molecular therapy has shown promise. This article summarizes the epidemiology, clinicopathologic features, natural history, and clinical management of GIST.

Gastrointestinal stromal tumors and leiomyosarcomas

Only recently has gastrointestinal stromal tumor (GIST) been recognized as the most frequent GI mesenchymal neoplasm. Prior to the use of KIT staining, most GI stromal tumors were identified as leiomyosarcoma (LMS). For primary GIST, surgery remains the principal treatment and adjuvant imatinib may improve outcomes. Multimodality therapy may also be effective in patients with metastatic GIST. In this review, we summarize the epidemiology, clinicopathologic features, natural history, and clinical management of LMS and GIST.

The role of KIT in the management of patients with gastrointestinal stromal tumors

In recent years, immunohistochemical staining for KIT (CD117) has become integral to the diagnosis of gastrointestinal stromal tumors (GISTs), nearly 90% of which harbor activating mutations in the KIT receptor tyrosine kinase gene. Approximately 80% of patients with metastatic GIST show at least some clinical response to the targeted small molecule KIT inhibitor imatinib. The response to imatinib is closely correlated with the presence and type of KIT mutation. GISTs with the most common KIT exon 11 mutations have the highest response rate by far, whereas GISTs lacking mutations in KIT or the alternative receptor tyrosine kinase PDGFRA show much lower rates of response to imatinib. Less than 5% of GISTs are KIT-immunonegative; and many of these tumors have activating mutations of PDGFRA, some of which are also inhibited by imatinib. Most patients who initially respond to imatinib become resistant and eventually progress, which coincides with the selection of imatinib-resistant secondary KIT mutations in the kinase domain. Sunitinib has recently been approved for patients with GIST, principally those who fail imatinib therapy; and additional small molecule inhibitors are in the pipeline. It is becoming evident that alternative approaches to direct KIT inhibition will be required for long-term survival of patients with advanced GISTs. This review examines the role of KIT in the diagnosis and management of patients with GIST.

Correlation of immunophenotype with progression-free survival in patients with gastrointestinal stromal tumors treated with imatinib mesylate

BACKGROUND

The therapy for gastrointestinal stromal tumor (GIST) has been revolutionized by imatinib mesylate (IM). It is unknown whether the levels of KIT expression or the presence of CD34, smooth muscle actin (SMA), desmin, or S-100 protein predicts patient outcome from IM therapy. In the current study, the prognostic effects for KIT and other proteins (CD34, SMA, desmin, S-100) were analyzed in a series of GISTs in which protein expression was evaluated by immunohistochemical analysis (IHC).

METHODS

The cases of 106 patients with GIST who were uniformly treated with IM at the study institution between December 15, 2000, and January 13, 2002 were evaluated retrospectively. The association between KIT intensity, CD34, desmin, SMA, S-100 protein, and progression-free survival (PFS) was studied. Kaplan-Meier analysis and the Cox proportional hazards regression model were used for statistical analysis.

RESULTS

The majority of tumors arose from the stomach (37%), small intestine (35%), and colorectum (14%). KIT expression as determined by IHC was categorized as weak (10%), intermediate (32%), or strong (58%). Patient tumors expressed CD34 (75%), SMA (56%), desmin (1%), and S-100 protein (32%). Patients whose GIST had weak, intermediate, or strong KIT expression were found to have an 18-month PFS rate of 80%, 84%, and 69%, respectively (P = .30). The presence or absence of CD34, SMA, desmin, or S-100 protein did not appear to correlate with PFS after IM.

CONCLUSIONS

Patients with the appropriate clinical presentation and KIT-positive GIST tumors appear to benefit from IM independent of the level of KIT or the expression of CD34, SMA, desmin, or S-100 protein by IHC.

Functioning paraganglioma and gastrointestinal stromal tumor of the jejunum in three women: syndrome or coincidence

Functioning paraganglioma and gastrointestinal stromal tumor (GIST) are uncommon tumors that occur mostly in a sporadic and isolated form, occasionally as components of multiple neoplasia syndromes, either separately or together. Separately, they occur in several inherited syndromes including multiple endocrine neoplasia 2, and the GIST, lentigines, and mast cell tumor syndrome. Together, they are variably prominent components of three syndromes: the familial paraganglioma and gastric GIST syndrome, neurofibromatosis type 1, and the Carney triad. The two former conditions are inherited as autosomal dominant traits; the latter does not appear to be inherited and affects young women predominantly. This article reports the nonfamilial occurrence of functioning paraganglioma and GIST of the jejunum in 3 women, 1 young (22 years) at initial presentation. The occurrences were unexpected because of the infrequency of the tumors. The neoplasms, respectively, did not show germline SDHA, SDHB, SDHC, and SDHD, and KIT mutations associated with familial paraganglioma and familial GIST. The paraganglioma-jejunal GIST combination may be the harbinger of a rare genetic syndrome, a variant of the Carney triad or the paraganglioma-gastric stromal sarcoma syndrome, or be coincidental.

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.

Localized intra-abdominal fibromatosis of the small bowel mimicking a gastrointestinal stromal tumor: A case report

Intra-abdominal fibromatosis (IAF) is a benign mesenchymal lesion that can occur throughout the gastrointestinal tract. Although rare, it is the most common primary tumor of the mesentery and can develop at any age. We describe a rare case of primary IAF involving the mesentery and small bowel which clinically, macroscopically and histologically mimicked malignant gastrointestinal stromal tumor (GIST). This report highlights the fact that benign IAF can be misdiagnosed as a malignant GIST localized in the mesentery or arising from the intestinal wall. Their diagnostic discrimination is essential because of their very different biological behaviors and the fact that the introduction of effective therapies involving tyrosine kinase inhibitor STI571 (imatinib mesylate) has greatly changed the clinical approach to intra-abdominal stromal spindle cell tumors.

Analysis of prognostic and immunohistochemical factors in gastrointestinal stromal tumors with malignant potential

The aim of this study was to analyze 37 patients with malignant primary gastrointestinal stromal tumors and to compare the findings and their therapeutic implications with those previously reported. The medical records of 37 patients who were diagnosed and operated on between January 1996 and December 2002 were retrospectively reviewed. The patients' age, tumor size, type of surgery, histologic type, mitotic counts, presence of necrosis, Ki-67 proliferative index, National Institutes of Health 2001 consensus classification, immunohistochemical staining, and recurrence were examined to analyze factors affecting survival. Overall actuarial survival for all patients was 46%. When analyzed by type of resection, the complete resection group (R0 resection) had a mean overall survival of 48.2 +/- 6.18 months compared with the patients with incomplete resection (R1-R2) who survived a mean of 10.8 +/- 3.2 months (P=0.00). Univariate analysis showed development of recurrence (P=0.00), tumor size of 8 cm or greater (P=0.05), Ki-67 proliferative index greater than 0.82 (P=0.0448), desmin staining (P=0.0076), age younger than 49 years (P=0.0009), and incomplete resection (P=0.00) to be significantly correlated with a poor survival. In multivariate analysis, desmin staining (P=0.031), tumor size (P=0.033), age (P=0.01), recurrence (P=0.038), and R0 resection (P=0.02) were significant independent prognostic factors. We recommend that more careful preoperative and more frequent postoperative follow-up examinations be performed for patients with large tumors, age of younger than 49 years, and Ki-67 proliferative index greater than 0.82.

Differential diagnosis of gastrointestinal stromal tumor and other spindle cell tumors in the gastrointestinal tract based on immunohistochemical analysis

To confirm the usefulness of an immunohistochemical panel of antibodies for KIT (c-kit/CD117), CD34, desmin, smooth-muscle actin (SMA), h-caldesmon (HCD), S-100 protein, neuron-specific enolase (NSE), and beta-catenin, 297 mesenchymal and peripheral nerve-sheath tumors of the gastrointestinal tract and intra-abdominal locations including 211 gastrointestinal stromal tumors (GISTs), 12 leiomyomas, 18 leiomyosarcomas, 17 solitary fibrous tumors (SFTs), 14 schwannomas, and 25 desmoid-type fibromatoses (DTFs) were analyzed immunohistochemically. Consistent (100%) immunoreactivity for KIT, CD34, desmin and S-100, and nuclear accumulation of beta-catenin were detected in GISTs, SFTs, smooth-muscle tumors, schwannomas, and DTFs, respectively. Immunoreactivity for SMA, HCD, and NSE was observed in a wide range of these tumors. In addition, 418 bone and soft tissue tumors were enrolled in this study for KIT immunostaining. As a result, a limited number of these tumors were KIT positive, including synovial sarcoma that showed morphological similarity to GISTs. These findings suggest that KIT, CD34, desmin, S-100, and beta-catenin are key markers for clinical diagnosis of GISTs and other spindle cell tumors that may involve the gastrointestinal tract, whereas SMA, HCD, and NSE have only limited value.

Biology of gastrointestinal stromal tumors: KIT mutations and beyond

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the digestive tract. Aspects of the morphology and immunophenotype in GISTs resemble those in the interstitial cells of Cajal (ICC), which are a specialized cell type responsible for coordinating peristaltic activity throughout the gastrointestinal tract. Therefore, it is possible that GISTs result from transformation of nonneoplastic progenitor cells that would normally differentiate towards an ICC endpoint. Activation of the KIT receptor tyrosine kinase is required for differentiation and proliferation of nonneoplastic ICC, and oncogenic KIT mutations are a crucial event in the development of most GISTs. These mutations can involve either the extracellular or intracellular domains of the KIT receptor, giving rise to conformational changes that enable constitutive, ligand-independent, activation of the KIT protein. Oncogenic KIT activation leads to phosphorylation of various substrate proteins and, in turn, to activation of signal transduction cascades regulating cell proliferation, apoptosis, chemotaxis, and adhesion. Recently, a small molecule tyrosine kinase inhibitor (STI571, imatinib mesylate, Gleevec) directed against the enzymatic (kinase) domain of the KIT protein was found to produce dramatic clinical responses as monotherapy for metastatic GISTs. This review focuses on the biological and molecular genetic principles of GISTs, and particularly the role of mutant KIT as a therapeutic target.

Malignant tumors of the small intestine

Malignant tumors of the small bowel are unusual and account for only 1% to 5% of all gastrointestinal tract malignancies. Thirteen cases of malignant tumors of the small bowel identified at the VAMC in Puerto Rico from January 1999 to September 2001 and a review of the literature are presented. The mean age of our cases was 67 (range: 45-78). Vague abdominal pain, nausea, vomiting, and melena were the most frequently reported symptoms. The average time from first symptoms to diagnosis was 3.2 months. A positive test for occult blood or hypochromic microcytic anemia was invariably present. Hyperbilirubinemia and increased alkaline phosphatase were warning signs that allowed earlier diagnosis in patients with duodenal tumors. Fifty-four percent of the lesions were detected by endoscopic examination while 46% relied on radiographic studies. Eleven had carcinomas and two malignant gastrointestinal stromal tumors. Neither carcinoids nor lymphomas were identified. Our report of thirteen cases of malignant small bowel tumors is unusual and exhibits differences with the previously reported data. The cases were identified in a limited Hispanic population in a short period of time. Aggressive evaluation and a high suspicion of these malignancies should be entertained whenever subtle symptoms and unexplained gastrointestinal blood loss are assessed.

Prognostic assessment of gastrointestinal stromal tumor

The term "gastrointestinal stromal tumor" (GIST) has been applied to a collection of distinctive mesenchymal tumors occurring within the human gastrointestinal tract. As new drug therapy becomes available, data regarding the natural history of these unusual tumors are necessary to provide selection factors for treatment. Ninety-eight patients had light microscopy compatible with GIST at a single institution from 1989 to 2000. After immunostaining with c-kit and histopathologic review, 69 were judged to be GIST. All prognostic indicators were determined for gastric GIST, intestinal GIST, and all locations combined. The location of the GIST did not have a significant impact on survival. Clinically, tumor size, peritoneal cancer index, and completeness of cytoreduction had a significant impact on prognosis for GIST at all locations. Pathologically, cytologic atypia, necrosis, invasion and number of mitoses were significant prognostic indicators for GIST. Criteria to separate three pathologic groups of GIST according to the tumor size and the mitotic count were useful to evaluate the tumor behavior; in the borderline pathologic group invasion and cytologic atypia were statistically significant prognostic criteria. The cell phenotypes, as determined by immunostains, correlated with the prognosis of gastric GIST but not intestinal GIST. A correlation between the immunostain Ki-67 but not CD-34 or desmin and the prognosis was observed. It is possible to select clinical and pathologic parameters of GIST that impact on prognosis. Invasion and necrosis help to determine the prognosis with borderline tumors. The immunostain Ki-67 correlated with the prognosis and may be helpful to assess prognosis when dealing with small biopsy specimens.

Frequent occurrence of low grade cases among metastatic gastrointestinal stromal tumours

AIM

Gastrointestinal stromal tumours (GISTs) are uncommon mesenchymal neoplasms. Some metastasise, whereas others remain asymptomatic for years, but it is difficult to distinguish between them histologically. This report analyses the characteristics of seven metastasising GISTs and compares clinicopathological parameters of the metastatic and non-metastatic groups.

METHODS/RESULTS

Histology revealed typical GIST features with spindle, epithelioid, or mixed appearance. All seven cases were positive for vimentin, five for neurone specific enolase, six for c-kit, four for S-100, three for PGP-9.5, three for CD-34 and synaptophysin, but all were negative for cytokeratin, neurofilament, chromogranin A, and desmin. Four showed a focal reaction for smooth muscle actin. Three of the tumours were GI, and two each were GII and GIII. The Ki-67 index varied from 4% to 44%, the three GI cases had 4%, 10%, and 16%. Tumours from the metastatic GIST group were significantly larger than those from the non-metastatic group.

CONCLUSIONS

Three cases exhibited bland, GI histological features with moderate or low proliferative activity. Among the c-kit positive metastasising stromal tumours, some were low grade, with moderate or low mitotic and Ki-67 indices, emphasising the necessity to develop a reliable grading system for GIST to predict clinical behaviour, the importance of careful analysis of "benign looking" tumours, and the key role of c-kit status in identifying patients who could benefit from treatment with STI-571. Larger tumours had a higher chance of metastasising, and only the size of the primary tumour played a role in predicting metastatic potential.

Interstitial Cells in the Musculature of the Gastrointestinal Tract: Cajal and Beyond

Expression of the receptor tyrosine kinase KIT on cells referred to as interstitial cells of Cajal (ICC) has been instrumental during the past decade in the tremendous interest in cells in the interstitium of the smooth muscle layers of the digestive tract. ICC generate the pacemaker component (electrical slow waves of depolarization) of the smooth musculature and are involved in neurotransmission. By integration of ICC functions, substantial progress has been made in our understanding of the neuromuscular control of gastrointestinal motility, opening novel therapeutic perspectives. In this article, the ultrastructure and light microscopic morphology, as well as the functions and the development of ICC and of neighboring fibroblast-like cells (FLC), are critically reviewed. Directions for future research are considered and a unifying concept of mesenchymal cells, either KIT positive (the "ICC") or KIT negative "non-Cajal" (including the FLC and possibly also other cell types) cell types in the interstitium of the smooth musculature of the gastrointestinal tract, is proposed. Furthermore, evidence is accumulating to suggest that, as postulated by Santiago Ramon y Cajal, the concept of interstitial cells is not likely to be restricted to the gastrointestinal musculature.

Gastrointestinal stromal tumors: chemotherapy and imatinib

Gastrointestinal stromal tumors (GISTs), previously thought to arise from the smooth muscles of the gastrointestinal tract, have recently been identified as a separate clinicopathologic entity. This new entity was revealed when investigations using more refined techniques suggested that GISTs had neural rather than smooth muscle differentiation and expressed the cell surface receptor Kit (CD117). Ensuing research led to development of a new molecularly targeted therapy, imatinib mesylate, which showed significant response among GIST patients in initial clinical trials. This review describes treatment of GIST before and after imatinib and the significance of this accomplishment.

Gastrointestinal stromal tumors: are they of cajal cell origin?

Recently some reports have suggested that gastrointestinal stromal tumors (GIST) might originate from the interstitial cells of Cajal or differentiate into them because they express c-kit and/or CD34 and indicated that the majority of previously diagnosed smooth muscle tumors (SMT) actually belong to GIST, but are not true SMT. We, therefore, detected c-kit, CD34, SMA, and S-100 in 106 Chinese cases of gastrointestinal tumors, which were histopathologically diagnosed as smooth muscle tumors originally, to demonstrate the immunophenotypes of these tumors. The results showed that 73 cases had immunoreaction with c-kit and/or CD34, of which 48 cases showed coexpression with either SMA or S-100 or with both. A correlation between the immunophenotypes and known histopathological parameters was also shown here based on follow-up data. We suggest that the concept of GIST should not be used as an umbrella to cover all gastrointestinal mesenchymal tumors, but be defined in a narrow term as differing from true smooth muscle tumors.

Gastrointestinal stromal tumors: an ultrastructural study

Gastrointestinal stromal tumors (GISTs) represent an enigmatic group of lesions of uncertain phenotype and biologic potential. Although earlier studies suggested smooth muscle cells, schwann cells, or neuronal differentiation, more recent evidence indicates that these tumors show phenotypic features that are similar to the interstitial cells of Cajal. Recently, investigators have begun to evaluate these lesions in a site-specific manner and have found that, in addition to morphologic differences between them, their biologic behavior also appears to be linked to their anatomic location. Many of these studies have emphasized the histologic and immunophenotypic features of GISTs in relation to their sites of origin, however, their site-specific ultrastructural characteristics have received little attention in the literature. In this study, we evaluated 34 GISTs (15 gastric, 12 small intestinal, 4 colonic, and 3 omental) for a variety of ultrastructural features in an effort to identify site-specific similarities and differences. Tumors predominantly composed of epithelioid cells were more commonly seen in gastric (60%) and omental (67%) tumors than in those of the small intestine (33%) and colon (0%). Cytoplasmic filaments and intercellular junctions were commonly seen in tumors from all locations, the filaments frequently forming paranuclear aggregates in the epithelioid cells. Tumors from all sites were composed of cells with surface filopodia and interdigitating cell processes, but in tumors of the stomach and omentum the filopodia were usually short and minimally intertwined, whereas those of small and large intestinal GISTs were characteristically long and complex. Basal lamina, though poorly formed, was present only in tumors of gastric and omental origin (13% and 67%, respectively). Pinocytotic vesicles were also seen in tumors from these sites (33% of gastric tumors and 67% of omental lesions) as well as those of the small intestine (17%) and the colon (25%). None of the gastric or omental tumors had microtubules; they were, however, seen in small intestinal (33%) and colonic (25%) stromal tumors. Skenoid fibers were seen in 33% of small intestinal GISTs and 1 metastatic gastric GIST. Overall, gastric and omental tumors have better developed features of myogenic differentiation and have blunt filopodia and minimally intertwined cell processes. Indeed, these 2 groups are indistinguishable ultrastructurally, raising the possibility that the genesis of omental GISTs is similar to that of gastric stromal tumors. Small intestinal stromal tumors have characteristic interdigitating cell processes and numerous elongate filopodia-like structures harboring intercellular junctions as well as microtubules and extracellular skenoid fibers. The constituent cells in colonic stromal tumors, while more reminiscent of small intestinal stromal, were frequently more primitive in appearance. In conclusion, GISTs from different anatomic locations share many overlapping ultrastructural characteristics; however, a few features are distinctive. It is hoped that these findings will aid in their recognition and contribute to the classification of this heterogeneous group of neoplasms.

Gastrointestinal stromal tumors in equids

Eleven gastrointestinal neoplasms from 10 aged horses and 1 pony were examined grossly, his tologically, immunohistochemically, and (in two cases) ultrastructurally. Clinical signs were associated with two neoplasms, and the other nine tumors were incidental findings at laparotomy or necropsy. The neoplasms were solitary (9/11) or multifocal (2/11), well demarcated, serosal or mural masses of stomach (1), jejunum (1), ileum (3), cecum (5), and/or colon (2). Microscopic examination revealed discrete spindle cells arranged in compact patterns with fascicles and whorls or cribriform pattern with fascicles and rare palisades, often with a myxoid interstitial matrix. Three tumors infiltrated between the muscularis interna and the muscularis externa at the myenteric plexi. All neoplasms were vimentin positive, 3/11 were S-100 positive, 2/11 were muscle actin positive, and no neoplasm was positive for glial fibrillary acid protein, desmin, factor VIII, chromogranin, or neuron-specific enolase. Of the two tumors studied ultrastructurally, one contained an admixture of smooth muscle cells and cells resembling Schwann cells, and the second was populated by homogeneous fusiform mesenchymal cells separated by homogeneous matrix. Gastrointestinal stromal tumors (GIST) have been recognized in humans, more recently in dogs and nonhuman primates, and now in equids. Most of these tumors are comprised of a loosely arranged network of spindled cells separated by myxoid matrix. GIST may be composed of myogenic, neurogenic, combined myogenic and neurogenic, and undifferentiated mesenchymal cells.

Familial multiple gastrointestinal stromal tumours with associated abnormalities of the myenteric plexus layer and skeinoid fibres

AIMS

Multiple familial gastrointestinal stromal tumours are rare. We report the third family with two cases of multiple gastrointestinal stromal tumours showing skeinoid fibres. Associated abnormalities of the myenteric plexus layer are described and new hypotheses for the histogenesis of gastrointestinal stromal tumours are formulated.

METHODS AND RESULTS

Multiple gastrointestinal stromal tumours developed in the duodenum and proximal jejunum were removed from mother and son. No history of a specific syndrome or of mastocytosis was known. Light microscopy revealed typical gastrointestinal stromal tumours with skeinoid fibres. An unusual abnormality of the myenteric plexus layer, showing a diffuse spindle cell hyperplasia, was noted in the macroscopically normal digestive wall. No abnormalities of the ganglion cells were associated. Tumours and the spindle cell hyperplasia showed similar morphological and immunohistochemical features with expression of CD34 and CD117 antigens. Follow-up revealed recurrences in the mother.

CONCLUSION

The morphological characteristics of these two cases of familial gastrointestinal stromal tumours and of the associated abnormalities of the myenteric plexus layer, help to better explain the histogenesis of multiple familial gastrointestinal stromal tumours. The hyperplasia of the myenteric plexus could be considered a risk factor for recurrent tumours.

Recent progress in the classification of soft tissue tumors: role of genetics and clinical implications

Soft tissue tumors comprise a vast and heterogeneous group of neoplasms. Because different tumors often have different biological behaviors and respond differently to various therapeutic modalities, precise classification is paramount. The majority of soft tissue tumors were first delineated on the basis of morphologic and clinical findings, which in many cases were adequate to accurately separate different tumors into homogeneous groups; however, it has increasingly been appreciated that many entities are actually heterogeneous groups of tumors that have similar histologic and pathologic characteristics but differ in their clinical behavior and underlying pathogenesis. Within the past several years, great strides have been made in the purification of different entities. This accomplishment has largely been because of advances in our understanding of the molecular genetics that underlie the pathogenesis of many sarcomas and the development of new and specific tumor markers. This review highlights some important recent work in two selected soft tissue tumors-gastrointestinal stromal tumor and inflammatory myofibroblastic tumor. These examples illustrate the type of progress that is being made in the classification of soft tissue tumors.

Gastrointestinal stromal tumors

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. A relationship to the interstitial cells of Cajal (ICCs) has been proposed, and expression of CD117, the c-kit receptor present in ICCs, has been suggested as a marker for GISTs.

METHODS

The English literature has been reviewed with an emphasis on histogenetic features, especially the potential relationship of GISTs to ICCs.

RESULTS

GISTs are most common in the stomach (70%), followed by small intestine (20%), colon and rectum (5%), and esophagus (<5%). GISTs commonly have activating mutations in exon 11 (or rarely exon 9 and exon 13) of the KIT gene that encodes a tyrosine kinase receptor for the stem cell factor or mast cell growth factor.

CONCLUSIONS

Malignant potential is best estimated by the simultaneous evaluation of several clinical parameters. The only absolute criterion for malignancy is tumor spread beyond the organ of origin at the time of diagnosis. The remarkable clinical response of tumors that express c-kit to treatment with the tyrosine kinase inhibitor STI571 is a triumph of molecular pharmacology.

The histopathological differential diagnosis of gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GISTs), initially presumed to be of "true" smooth muscle origin, encompass a heterogeneous, and as yet incompletely understood, group of mesenchymal tumours with respect to their origin, cellular differentiation, and prognosis. Cellular morphology ranges from predominantly spindle shaped to epithelioid in character, whereas differentiation pathways, as determined primarily by immunohistochemistry and ultrastructure, can vary from indeterminate to myoid and/or neural. Recent work has indicated that the interstitial cells of Cajal, a complex cellular network postulated to act as pacemaker cells of the gastrointestinal tract, which exhibit both myoid and neural features, could be candidates for tumour histogenesis. This would provide a plausible and attractive explanation for the variable differentiation pathways identified in the GIST category to date. Nevertheless, the occasional but undisputed location of GISTs outside the gastrointestinal tract (omentum, peritoneum, and retroperitoneum) might mitigate against such an origin, and their histogenesis remains open to debate. The c-kit proto-oncogene, encoding a growth factor receptor with tyrosine kinase activity, has been postulated to play an important role in tumorigenesis because "gain of function" mutations in this gene, localised to chromosome 4q11-21, are being increasingly identified in hereditary and sporadic cases. Monoclonal and polyclonal antibodies directed at the c-kit gene product expressed on the cell surface (CD117/c-kit) appear to be increasingly helpful in resolving the histopathological differential diagnosis between GISTs and true gastrointestinal smooth muscle neoplasms, schwannomas, and other far less frequently occurring mesenchymal tumours at this site. Although tumours with a clinically benign course appear to be more common than their malignant counterparts, no specific histological criteria have as yet been identified to enable an unambiguous prediction of biological behaviour. Increasing tumour size and mitotic activity favour aggressive tumour behaviour, whereas the prognostic value of germline and somatic mutations within the c-kit proto-oncogene remains to be elucidated further. It is the aim of this synopsis to highlight the relevant fundamental and diagnostic developments with respect to this complex group of neoplasms.

Diagnosis of gastrointestinal stromal tumor by fine-needle aspiration biopsy: a cytological and immunocytochemical study

The diagnosis of gastrointestinal stromal tumors (GIST) is generally established on histopathologic examination of surgical specimens. The present study was undertaken to characterize the cytologic appearance of these tumors and to assess the utility of fine-needle aspirates, including immunocytochemistry for the demonstration of c-kit (CD117) and CD34, in the preoperative diagnosis. The study comprised preoperative fine-needle aspirates in three cases and aspirates performed on fresh surgical specimens in eight cases. The routinely stained smears revealed a mesenchymal cell population, predominated by spindle cells. In five of six cases a strong positivity for c-kit was demonstrated and in three of five cases a strong CD34-expression was found in the tumor cells. These results show that fine-needle aspiration appears to be a useful method for the recognition and diagnosis of GISTs or ICC (interstitial cell of Cajal) tumors.

Cytomorphology of gastrointestinal stromal tumor: diagnostic role of aspiration cytology, core biopsy, and immunochemistry

Gastrointestinal stromal tumors (GISTs) comprise a heterogeneous group of neoplasms of the gastrointestinal tract previously referred to as leiomyomas, leiomyosarcomas, or schwannomas. GISTs derive from the interstitial cell of Cajal and, in addition to variable expression of smooth muscle and neural markers, they characteristically express CD34 and CD117. To our knowledge, the cytologic appearance of gastric neoplasms designated as GISTs has never been reported. We illustrate the fine-needle aspiration (FNA) cytology findings of a gastric stromal tumor having spindle cells with delicate cytoplasm and prominent nuclear palisading. Consistent core biopsy and immunochemistry findings further supported the diagnosis of GIST. Pathologic evaluation of the resected tumor confirmed the cytologic diagnosis. In the appropriate clinical and radiologic setting, a confident diagnosis of GIST can be established by FNA cytology and core biopsy. The roles of immunochemical stains and other ancillary techniques in reaching the correct diagnosis are addressed.

Gastrointestinal stromal tumor versus intra-abdominal fibromatosis of the bowel wall: a clinically important differential diagnosis

Intra-abdominal fibromatosis (IAF) is an uncommon benign neoplasm that usually occurs in the mesentery or retroperitoneum and may, on occasion, mimic a gastrointestinal stromal tumor (GIST). Differentiating between these two entities is important clinically because IAF is a benign tumor whereas GISTs frequently have malignant potential. In this study, the authors identified 13 cases of IAF with prominent involvement of the bowel wall as well as 35 GISTs of the small intestine, colon, or mesentery and analyzed their clinical, gross, histologic, immunophenotypic, and ultrastructural characteristics to identify important distinguishing features. Patients with IAF were younger (mean, 34 yrs) than patients with GIST (mean, 54 yrs). Both types of tumors tended to be large, but GISTs were soft and lobulated with hemorrhage, necrosis, or cystification whereas IAFs were firm, tan, and homogeneous. Histologic features characteristic of GIST included the presence of spindle or epithelioid cells with variable architecture, mitotic activity (range, <1-95 mitoses/50 high-power fields [hpf]; mean, 15 mitoses/50 hpf), nuclear atypia, and myxoid or hyalinized stroma. Necrosis and hemorrhage were seen in 16 and 25 tumors, respectively. In contrast, IAFs were composed of broad, sweeping fascicles of monotonous spindle cells with mitotic activity (range, <3-11 mitoses/50 hpf; mean, 4 mitoses/50 hpf), bland nuclear features, and finely collagenous stroma. Necrosis, hemorrhage, and myxoid degeneration were not seen. Immunohistochemical studies performed on a limited number of GISTs and IAFs demonstrated that cells expressed vimentin (100% GIST and IAF), CD117 (88% GIST and 75% IAF), CD34 (42% GIST and 0% IAF), smooth muscle actin (63% GIST and 75% IAF), muscle actin (75% GIST and 75% IAF), desmin (8% GIST and 50% IAF), and S-100 protein (16% GIST and 0% IAF). Ultrastructural analysis of 21 GISTs revealed incomplete smooth muscle differentiation in some tumors whereas IAFs were shown to have complete myofibroblastic/fibroblastic differentiation. Information regarding clinical outcome was available on 29 patients and revealed that three patients with histologically benign GISTs were alive with no evidence of disease at 5 months to 6 years (mean, 3.5 yrs) and one patient with a histologically benign tumor died of disease after 7 years. Of patients with histologically malignant GIST, one died of surgical complications, 10 were alive without disease at I to 13 years (mean, 5.4 yrs), four were alive with disease at 4 months to 15 years (mean, 3.8 yrs), three had disseminated disease at operation, and seven were dead of disease at 10 months to 3 years (mean, 2.2 yrs). Follow up of eight patients with IAF demonstrated that five were alive without disease at 4 months to 15 years (mean, 5.3 yrs) and three had recurrences at 1 (two patients) and 2 years (one patient). In summary, IAFs can have many features (large size, infiltration of adjacent structures, mitotic activity) that can cause diagnostic confusion with GISTs and, importantly, the degree of mitotic activity present in IAFs may overlap that seen in malignant GISTs. These entities can be distinguished primarily by their light microscopic and ultrastructural features but there is a notable overlap in their immunohistochemical profiles. The distinction between these neoplasms is important because there are important clinical implications for the patient.

Extragastrointestinal (soft tissue) stromal tumors: an analysis of 48 cases with emphasis on histologic predictors of outcome

The clinicopathologic features of 48 tumors that were histologically similar to gastrointestinal stromal tumors but occurred in the soft tissues of the abdomen were analyzed to determine their overall similarity to their gastrointestinal counterpart, their biologic behavior, and the parameters that predict risk for adverse outcome. Classic leiomyomas and leiomyosarcomas were specifically excluded. The tumors occurred in 32 women and 16 men, who ranged in age from 31 to 82 years (mean, 58 years). Forty tumors arose from the soft tissue of the abdominal cavity, and the remainder arose from the retroperitoneum. They ranged in size from 2.1 to 32.0 cm and varied from tumors composed purely of rounded epithelioid cells to those composed of short fusiform cells set in a fine fibrillary collagenous background with some cases showing a mixed pattern. Tumors displayed variable amounts of stromal hyalinization, myxoid change, and cyst formation. The tumors expressed CD117 (c-kit receptor) (100%), CD34 (50%), neuron-specific enolase (44%), smooth muscle actin (26%), desmin (4%), and S-100 protein (4%). Tumors were evaluated with respect to several parameters: size (<10 cm or >10 cm), cellularity (low or high), mitoses (0 to 2 per 50 high-power fields, >2 per 50 high-power fields), nuclear atypia (1 to 3+), cell type (epithelioid, spindled, or mixed), and necrosis (absent or present). These parameters were then evaluated in univariate and multivariate analysis with respect to adverse or nonadverse outcome, the former defined as metastasis or death from tumor. Follow-up information was obtained for 31 patients (range, 4 to 84 months; median, 24 months). One patient presented with an adverse event and, therefore, was excluded from subsequent analysis. Twelve patients (39%) developed metastases or died of tumor. In univariate analyses, cellularity, mitotic activity (>2 per 50 high-power fields), and necrosis were associated with statistically significant increases in the risk for adverse outcome. Despite the relatively small sample size, in a multivariable analysis mitotic activity (relative risk, 7.46; P = .09) and necrosis (relative risk, 3.75; P = .07) displayed trends toward independent predictive value. No association was noted between histologic pattern and outcome. Although only 39% of tumors behaved in a malignant fashion, this figure probably represents a conservative estimate because long-term follow-up (>5 years) was available for only a limited number of patients. Stratification of patients who have extragastrointestinal stromal tumor into those with 0 to 1 adverse histologic factors versus those with 2 to 3 offers the advantage of separating patients into two groups that have a markedly different risk for adverse outcome in the short term (0.02 events versus 0.54 events per person-year; P < .001, respectively). Extragastrointestinal (soft tissue) stromal tumors are histologically and immunophenotypically similar to their gastrointestinal counterpart but have an aggressive course more akin to small intestinal than gastric stromal tumors.

Molecular Insights into the Histogenesis and Pathogenesis of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) have long been problematic in terms of classification and determination of prognosis. Recent studies have suggested that GISTs differentiate toward a phenotype resembling the interstitial cells of Cajal. This has led to the important discovery that activating mutations in the KIT receptor tyrosine kinase play an important role in the pathogenesis of GISTs. These findings have helped clarify the distinction between GISTs and other mesenchymal neoplasms of the gastrointestinal tract and may translate into an improved ability to predict biologic behavior, as well as suggesting possible avenues for rational drug design for the treatment of GISTs. Int J Surg Pathol 8(1):5-10, 2000

Salvage surgery for patients with recurrent gastrointestinal sarcoma: prognostic factors to guide patient selection

BACKGROUND

Gastrointestinal sarcomas are rare stromal tumors and most are classifiable as malignant gastrointestinal stromal tumors. They have a high propensity for intraabdominal recurrence. It is unclear whether there is a survival advantage from reoperation for recurrent disease or if surgery should be confined to symptom relief. The authors have attempted to identify features that may allow the selection of patients most likely to benefit from reoperation.

METHODS

Retrospective univariate and multivariate analyses of 60 patients with recurrent gastrointestinal sarcoma, accrued from a prospective data base between July 1982 and September 1995, were performed.

RESULTS

Initial recurrence was evident by a median of 20 months from primary resection. Most patients (85%) had an initial symptomatic recurrence. Local recurrence was seen in 76% of patients, but in half of these synchronous hepatic metastases were present. None had disease outside of the abdomen. Complete resection of recurrent disease was possible in only one-third of cases. Median survival after surgery for recurrence was 15 months, but was longest for patients whose recurrence took the form of liver metastases in the absence of disease elsewhere. In multivariate analysis of post-recurrence survival, the only significant determinant of survival was the length of the disease free interval between the initial operation and recurrence.

CONCLUSIONS

Survival following recurrence of a gastrointestinal sarcoma is largely determined by the tumor biology, one manifestation of which is the disease free interval. Except for patients with a long disease free interval, surgery should be reserved largely for symptom control.

High mitotic index associated with poor prognosis in gastrointestinal autonomic nerve tumour

AIMS

Three gastrointestinal autonomic nerve tumours (GANT) were characterized by immunohistochemistry and flow cytometry. Two of the three cases occurred in the small intestine, while the third was found in the stomach. Besides the immunohistochemical and ultrastructural description, the aim of this study was to examine the relation between the known and accepted predictive factors (ploidy data, the S-phase fraction, the mitotic and MIB-1 index and the size of the tumour) and the survival of the patients.

METHODS AND RESULTS

The immune profile showed that 3/3 cases were vimentin and NSE, 2/3 were synaptophysin and PGP 9.5 positive, while 1/3 also showed S100 positivity. Ultrastructurally, all the cases had dense core granules, one of them contained skenoid fibres. The flow cytometry revealed diploid DNA in all cases, however, significant differences could be seen in the proliferative activity of the individual neoplasms.

CONCLUSIONS

In spite of the published data of gastrointestinal stromal tumours (GIST) generally, neither the MIB-1 index and the ploidy data nor the size of the primary tumour helped to predict the clinical progression of the examined GANTs. However, the high proliferative activity (57 mitoses/10 HPF) and the elevated S-phase fraction (24%) was associated with advanced, metastatic and recurring disease in case 3. On the basis of these three cases, high mitotic activity is the most reliable factor in predicting aggressive clinical behaviour.

Stromal tumors of the abdominal colon: a clinicopathologic study of 20 cases

Stromal tumors of the abdominal colon, the least common of all gastrointestinal stromal tumors, have not been well characterized. They have often been lumped with stromal tumors of the anorectum in order to achieve significant numbers for analysis, yet there are no data to prove that stromal tumors from these two sites are the same. In this study, we evaluated 20 colonic stromal tumors to identify clinical, morphologic, and immunophenotypic features that were useful in discriminating between those that had metastasized or caused death from those that had not metastasized or caused death. We found that colonic stromal tumors are morphologically heterogeneous, and the malignant ones are clinically aggressive. They often have metastases at presentation, and cause death in a short time. An infiltrative growth pattern in the muscularis propria, invasion of the mucosa, and high mitotic counts correlated significantly both with metastases and with death from tumor. We also found that dense cellularity correlated significantly with metastases, but not with death, and that coagulative necrosis correlated with death, but not with metastases.

Expression of c-kit (CD117) and Ki67 provides information about the possible cell of origin and clinical course of gastrointestinal stromal tumours

AIMS

Gastrointestinal stromal tumours (GIST) were analysed to determine their immunophenotype with emphasis on the expression of CD34 and c-kit and to identify a possible cell of origin. Furthermore, the aim was to correlate clinical, histological and immunophenotypic parameters to their clinical course by means of statistical analysis.

METHODS AND RESULTS

An immunohistochemical analysis was performed on 64 cases of GIST. Three of the tumours displayed an immunohistochemical phenotype compatible with the diagnosis of leiomyomatous tumour. Almost half the tumours were stained positively for CD34 and 48 of 61 tumours were positive for c-kit (CD117), a marker of haematopoietic progenitor cells, mast cells and the so-called interstitial cell of Cajal (ICC). In most of the cases, the staining was strong and evenly distributed within the tumours. Statistical analysis on 31 cases with an appropriate follow-up time, showed that the expression of Ki67 in the nuclei of the tumour cells was the most important prognostic factor.

CONCLUSIONS

Judging from the results of the immunohistochemistry, there would appear to be some justification for suggesting a label of ICC tumours for these c-kit-positive tumours without any other obvious phenotype. A discriminant function analysis allowed 90.3% of patients to be correctly classified in prognostic terms from data on Ki67 and CD34 expression, grade, size and patient age.

Benign schwannoma of the digestive tract: a clinicopathologic and immunohistochemical study of five cases, including a case of esophageal tumor

We report five cases of schwannomas of the digestive tract. The patients were two men and three women, whose ages ranged from 56 to 74 years. Three cases arose in the stomach, one in the ascending colon, and one in the esophagus; the latter was a hitherto unreported location for this tumor. The schwannomas ranged from 2 to 11 cm in diameter. They were well circumscribed but not encapsulated, with interlacing bundles of spindle cells, nuclear atypia and no mitosis, interspersed with collagenous strands. Inflammatory cells were scattered throughout the tumors and a peripheral cuff of lymphoid aggregates was observed in all cases. Intracellular periodic acid-Schiff (PAS)-positive crystalloids were found in three cases; no skeinoid fibers were seen. A diffuse and intense positivity for vimentin and S-100 protein was detected in all five cases together with a variable and sometimes focal positivity for glial fibrillary acidic protein and neuron-specific enolase. None of the tumors showed expression of CD34 or the smooth muscle antigens tested. The four cases with a sufficient follow-up had a favorable outcome without any recurrence or metastasis. The morphologic and immunohistochemical features of digestive schwannomas were compared with those of other gastrointestinal stromal tumors. Schwannomas have many differences. Digestive schwannomas can be readily recognized on histologic and immunohistochemical examination. They are spindle cell tumors without epithelioid features, with a peripheral cuff of lymphoid tissue. Specific intracellular needle-shaped PAS-positive crystalloids are found in some cases, whereas skeinoid fibers are not. These tumors always express S-100 protein in a diffuse and strong manner, and they express glial fibrillary acidic protein but not express CD34. Digestive schwannomas usually are gastric tumors and have never been reported in the small bowel. They pursue a benign course and are far rarer than gastrointestinal autonomic nerve tumors.

Immunophenotype, proliferation, DNA ploidy, and biological behavior of gastrointestinal stromal tumors: a multivariate clinicopathologic study

To determine the prognostic impact of clinical, immunohistochemical, and biological parameters, we examined 52 gastrointestinal stromal tumors (GIST) by conventional light microscopy and immunohistochemistry. DNA ploidy was analyzed by image cytometry on cytospin preparation. The proliferative activity was determined by mitosis counting and assessment of Ki-67 reactivity by means of monoclonal antibody Ki-S5. A histopathologic grade was assigned to each tumor according to the French Federation of Cancer Centers (FNCLCC) grading system. Next to vimentin, CD34 was the most prevalent antigen, followed by markers of neural and muscular differentiation. Many tumors exhibited a mixed phenotype. Twenty-one tumors were diploid, eight hypodiploid, and 23 aneuploid. In univariate analysis, tumor grade, Ki-S5 labeling index, mitotic count, atypical mitoses, cellularity, and sex were predictive of both mortality and metastasis risk. DNA ploidy only correlated with overall survival, whereas the tumor location affected the occurrence of metastases. Multivariate analysis selected Ki-S5 scores (P < .0001) and atypical mitoses (P=.012) as independent prognosticators for overall survival, and tumor grade (P=.0036) and size (P=.0055) as predictors of metastatic spread. We conclude that GIST are primitive mesenchymal tumors capable of divergent differentiation, which does not influence their prognosis. The latter appears to be best predicted by histopathologic grading and the Ki-67 labeling index.

Numerous eosinophilic globules (skeinoid fibers) in a duodenal stromal tumor: an exceptional case showing smooth muscle differentiation

A unique case of duodenal stromal tumor in a 51-year-old man is reported. The tumor histologically showed spindle cell proliferation and numerous eosinophilic globules. Most globules were composed of tangled 45 nm thick fibrils, which were ultrastructurally identical to 'skeinoid fibers'. The presence of glycogen granules in the tumor cells and the immunoreactivity for alpha-smooth muscle actin suggested smooth muscle differentiation. Focal ultrastructural findings also supported the smooth muscle nature of this tumor. There were no immunohistochemical and ultrastructural features indicating neural differentiation. In previous studies, the presence of such 'skeinoid fibers' was suggested to be a histological marker for neural differentiation in gastrointestinal stromal tumor. However, the findings in the present case suggest that numerous 'skeinoid fibers' can be identified in duodenal stromal tumor with smooth muscle differentiation, although this condition may be rare.

Expression of myogenic marker proteins in human leiomyosarcoma

A series of formalin-fixed, paraffin-embedded leiomyosarcomas (n = 11) was studied immunohistochemically for their expression of various myogenic marker proteins. According to their predominant histological appearance, the tumors were classified as well (n = 4), moderately (n = 5), or poorly (n = 2) differentiated. Using monoclonal anti-muscle specific actin antibodies from clone HHF35 all examined tumors were positively stained. Desmin was not always found in leiomyosarcomas, since positive staining could be demonstrated only in eight cases. As revealed by staining with anti-vinculin antibodies from clone hVIN-1 using the APAAP technique, all leiomyosarcomas with the exception of one expressed vinculin. Typically, the vinculin immunoreactivity was detected diffusely throughout the majority of neoplastic cells as well as in vascular smooth muscle cells of blood vessels. Nine leiomyosarcomas displayed a positive staining for calponin, an actin-binding protein expressed in smooth muscle cells and their precursors. The distribution of calponin resembled that of vinculin in decorating myofibrils of nearly all tumor cells. Actinin immunoreactivity was present in tumor cells of all cases, but was expressed also in nontumor cells such as epithelia. These results suggest that the monoclonal antibodies against vinculin and calponin may serve as additional diagnostic markers for myogenic differentiation in leiomyosarcomas and related tumors.

Gastrointestinal autonomic nerve tumor with giant abscess. A case report and literature review

We report a gastrointestinal autonomic nerve tumor of the stomach with a giant abscess. The patient had fever and pain and was found to have anemia and an abdominal mass. X-ray and endoscopic examination showed a gastric submucosal tumor with a fistula to the gastric lumen. Partial gastrectomy was performed and no metastasis was found. On gross examination, the excised tumor was seen to be a submucosal solid tumor with a giant abscess. Alpha streptococci and anaerobic gram-negative rods were cultured from the pus of the abscess. The tumor resembled a gastric myogenic tumor composed of spindle cells, partly showing storiform and epithelioids. Tumor cells showed positive staining for vimentin and neuron-specific enolase but were negative for desmin, alpha-smooth muscle actin, and S-100 protein. Ultrastructural examination showed remarkable interdigitation of cytoplasmic processes with neurosecretory granules between the tumor cells. This lesion was similar to previously described gastrointestinal autonomic nerve tumors. Gastrointestinal autonomic nerve tumors are a rare, distinct subtype of gastrointestinal stromal tumors; although several cases of focally necrotic tumors have been reported, there has been only one report of the tumor with an abscess, as in our case.

Stromal cell tumour of rectum treated by transanal endoscopic microsurgery

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Multiple small intestinal stromal tumors with skeinoid fibers in association with neurofibromatosis 1 (von Recklinghausen's disease)

A case of multiple small intestinal stromal tumors (SIST) with skeinoid fibers of the jejunum arising in a 50 year old male with neurofibromatosis 1 (NF-1) is reported. Seven small tumors of the jejunal wall were incidentally found and excised during an operation for abdominal and retroperitoneal neurofibromas. Histologically, the tumors were composed of uniform spindle-shaped cells with fascicular pattern, almost indistinguishable from the histology in leiomyoma. Periodic acid Schiff stain-positive hyaline globules were observed among the tumor cells. Ultrastructurally, these globules were stromal tangles of curvilinear, fluffy fibrils, consistent with skeinoid fibers. The electron-dense granules, possibly neuro-secretory granules, were found in the cytoplasm of the tumor cells. Immunohistochemically, the tumor cells were positive for vimentin, neuron specific enolase and CD34, but negative for muscle markers and S100 protein. The association of NF-1 and multiple SIST with skeinoid fibers may have clinical implications. The multiple occurrence of SIST with skeinoid fibers seems to be often cited as one of the gastrointestinal manifestations of NF-1. The possible site of origin of SIST with skeinoid fibers in NF-1 may be the enteric autonomic nerve plexus in the small intestinal wall.

Subclassification of gastrointestinal stromal tumors based on evaluation by electron microscopy and immunohistochemistry

Fifty-six gastrointestinal stromal tumors (GIST) were subclassified by ultrastructural examination and by immunophenotypic analysis using a panel of 13 antibodies. Eighty percent of the tumors originated in the stomach and small intestines. The neoplasms were classified as follows: 42.9% smooth muscle tumors (4 leiomyomas, 9 spindle cell and 8 epithelioid leiomyosarcomas, and 3 mixed spindle cell and epithelioid leiomyosarcomas); 37.5% gastrointestinal autonomic nerve tumors (GANT), 47.6% of which arose in the small intestines; 8.9% mixed leiomyosarcoma/neurogenic tumors; and 10.7% undifferentiated GIST, not otherwise specified. The muscle common actin antibody HHF-35, variably reactive with tumor cells composing 23 of 24 smooth muscle tumors, was found to be the most sensitive marker of leiomyocyte differentiation. One immunophenotypically questionable spindle cell leiomyosarcoma was diagnosed by electron microscopy. Since neuron specific enolase positive cells were found in 1/3 of the leiomyosarcoma cases, the ultrastructural demonstration of synapse-like structures and neurosecretory granules was required for diagnosing GANTs. The immunophenotype of the ultrastructurally undifferentiated GIST was vimentin and CD34+. Variable numbers of ultrastructurally undifferentiated cells also we found in all of the tumors except 2 leiomyomas. CD34 was also expressed in smooth muscle (54%) and GAN (62%) tumors. Despite their similar light microscopic appearance, GIST are phenotypically heterogeneous, requiring both ultrastructural and immunohistochemical studies for accurate characterization.

Use of monoclonal antibody 1H1, anticortactin, to distinguish normal and neoplastic smooth muscle cells: comparison with anti-alpha-smooth muscle actin and antimuscle-specific actin

In preliminary experiments, we found that 1H1, a monoclonal antibody directed against the v-src substrate cortactin, reacts with smooth muscle, myoepithelium, myofibroblasts, and macrophages in formaldehyde-fixed human tissues. To evaluate the use of this antibody as a diagnostic reagent, we tested the immunohistochemical distribution of cortactin in 61 mesenchymal neoplasms, 11 neuroectodermal neoplasms, and eight embryonal epithelial neoplasms. The results were compared with those obtained using antibodies against alpha-smooth muscle actin and muscle-specific actin on a similar set of tissues. With the exception of positive staining in rhabdomyosarcoma, in this series only tumors with smooth muscle differentiation appeared to contain cortactin (16 of 19 leiomyosarcomas, one infantile fibrosarcoma, one malignant fibrous histiocytoma). Immunoelectron microscopy localized cortactin to the actin-associated dense bodies of the microfilament network. We conclude that cortactin may be a useful adjunct to alpha-smooth muscle actin and muscle-specific actin as a marker for the study and diagnosis of smooth muscle neoplasms and related lesions.

Duodenal leiomyosarcoma presenting with iron deficiency anemia

Failed iron therapy warrants investigation to rule out disorders of iron absorption or intestinal blood loss. The authors report the third case of duodenal leiomyosarcoma in childhood, which presented with iron deficiency anemia. Endoscopy failed to elicit the cause of this problem. Wide surgical resection, sparing the pancreas, was possible.

Gastrointestinal autonomic nerve tumor: a case report with electron microscopic and immunohistochemical analysis and review of the literature

A case of an adolescent girl with metastatic gastric stromal tumor is described. There were three metastatic nodules in the liver at the time of the admission. A subtotal gastrectomy was performed. The tumor had distinctly nodular appearance and was composed of a variety of cells suggestive of smooth muscle differentiation. Electron microscopy revealed cytoplasmic neural processes and densecore neurosecretory granules. Immunohistochemistry showed positive neuron-specific enolase, synaptophysin, and chromogranin A in some of the tumor cells. Similar findings in the primary tumor and its liver metastases indicated a primitive neural differentiation and enabled us to classify the lesion as a gastric autonomic nerve tumor. No other tumors that would suggest that the gastric lesion is a part of Carney's triad were detected. The child was treated with chemotherapy but the liver metastases did not change significantly. She is alive with unresectable liver metastases 10 months after the gastrectomy.

CD34 immunoexpression in stromal tumours of the gastrointestinal tract and in mesenteric fibromatoses

The aim of this study was to explore whether CD34 immunoreactivity can distinguish between different types of gastrointestinal stromal tumour, i.e. smooth muscle and neurogenic. We studied 87 stromal tumours from different sites in the gastrointestinal tract, as well as the omentum and mesentery, using a monoclonal antibody to CD34 (QBEND10). We also determined the immunoexpression of smooth muscle and muscle specific actins, S-100 protein, cytokeratin, desmin and vimentin. In addition, 15 cases of mesenteric fibromatosis were tested for CD34. Immunoexpression of CD34 was observed in 40 of the 87 stromal tumours and correlated with evidence of differentiation towards a smooth muscle phenotype. Large intestinal stromal tumours were less likely than gastric lesions to be CD34 positive. None of 15 cases of mesenteric fibromatosis was positive for CD34. We conclude that CD34 immunoexpression is seen in a proportion of stromal tumors of the gastrointestinal tract, mesentery and omentum, particularly those of smooth muscle type, and it may be useful as part of an immunohistochemical panel in the differential diagnosis of these neoplasms.

Desmin and neural marker expression in mesothelial cells and mesotheliomas

The distribution of keratin, vimentin, desmin, muscular actin, S100, specific neuron enolase, and chromogranin was studied by immunoperoxidase staining in mesothelium, malignant mesotheliomas, and pulmonary carcinomas. The mesothelial cells were positive for keratin and vimentin on all smears of pleural and ascitic effusions; most of them were also positive for desmin but rarely for enolase and S100. None was positive for muscular actin. Sixteen malignant mesotheliomas expressed vimentin and keratin; six were also positive for desmin, three for desmin and neural markers, and five for neural markers. In comparison, none of the pulmonary carcinomas was positive for these markers. Mesothelial cells are able to express markers of divergent differentiation. Mesotheliomas also have such markers that are present in other malignant tumors and, in particular, in intra-abdominal desmoplastic small cell tumors with divergent differentiation. This entity and mesotheliomas probably originate from the same cell. Moreover, desmin, found in 56% of malignant mesotheliomas but absent in pulmonary carcinomas, may be useful in the differential diagnosis of these tumors.