Small Intestinal Stromal Tumors With Skeinoid Fibers

Structural variations of collagen in normal and pathological tissues: role of electron microscopy

The spectrum of ultrastructural appearances assumed by collagen in normal and pathological tissues is illustrated using techniques of thin section transmission electron microscopy and computer-assisted analysis. The normal fibrillar collagen types are described in order to provide a basis for comparing other normal and abnormal forms. In normal tissues, the anchoring fibril and basal lamina (basement membrane) represent tissue structures largely containing collagen but differing significantly in organisation from normal types I to III fibrillar collagen. In pathological tissue, deviations from normal fine structure are reflected in abnormal aggregates of collagen fibrils (amianthoid and skeinoid fibres) and abnormalities in fibril diameter and cross-sectional profile. Fibrous and segment long-spacing collagen represent two further organisational variants of collagen, the former found widely in pathological tissues, the latter very rarely. Much remains to be discovered about these abnormal collagen variants-their mode of formation, the cells that produce them, and their roles. They also present a challenge for the collagen biologist formulating hypotheses of collagen fibril assembly and molecular organisation.

Plexosarcoma: endoscopic ultrasound and electron-microscopic characteristics of a stromal tumor

Endoscopic ultrasound is useful for managing submucosal masses; however, some of these lesions can be difficult to classify except with full histological and electron microscopic evaluation. A 72-yr-old woman was seen with upper GI bleeding. Endoscopy showed a 1.7-cm sessile ulcerated submucosal mass in the duodenal bulb. Endoscopic ultrasound revealed an echolucent submucosal mass arising from the fourth echolayer, the muscularis propria of the duodenal wall. These findings suggested that the lesion was a leiomyoma. The patient eventually had the lesion resected because of recurrent bleeding. Histologically it was a spindle cell tumor that on electron microscopy showed neuronal elements consistent with a plexosarcoma, or gastrointestinal autonomic nerve tumor. These lesions account for some one third of all gastrointestinal stromal tumors. Despite their low grade malignant histologic appearance, local recurrence or hepatic metastases occur in about 70% of patients.

Congenital gastrointestinal stromal tumour is morphologically indistinguishable from the adult form, but does not express CD117 and carries a favourable prognosis

AIMS

The histological and immunohistochemical features of a congenital stromal tumour of the jejunum are compared with those of adult gastrointestinal stromal tumours (GIST). The literature concerning the diagnosis and prognosis of congenital small intestinal stromal tumours is reviewed.

METHODS AND RESULTS

A term female infant presented with intestinal obstruction, from birth. Histology of a 15-mm jejunal nodule showed a predominantly spindle-cell tumour with epithelioid areas. There was a low mitotic count and mild nuclear pleomorphism, extensive necrosis and haemorrhage, and focal calcification. Immunohistochemically, tumour cells stained for muscle specific actin and vimentin. Staining for CD117 (c-kit), S100, desmin and CD34 was negative. The features were compared to those of seven adult cases: no morphological feature was specific to the congenital tumour, which was smaller than the adult cases. There were no ultrastructural features specific for a particular line of differentiation. Immunohistochemical staining patterns were similar, except for CD117, which was strongly positive in all adult tumours, but negative in the congenital tumour.

CONCLUSIONS

This congenital jejunal stromal tumour morphologically resembled adult GIST, but lack of c-kit expression suggests that it is nosologically distinct. Despite the presence of histological features which would cause the tumour to be categorized as malignant in an adult, it is apparent from previous reports of congenital small intestinal stromal tumours that the prognosis is favourable.

Gastrointestinal stromal tumor with skeinoid fibers of the ileum

Gastrointestinal stromal tumor (GIST) is not uncommon among gastrointestinal nonepithelial tumors, but there are few reports describing the cytologic findings. We report a case of GIST with skeinoid fibers in scrape cytology preparation. The patient was a 53-year-old man with a tumor in the small intestine. Scrape preparations from the cut surface of the resected tumor revealed cellular material composed of spindle cells showing loose clusters or single cells. The nuclei were spindled, elongated or cigar-shaped, and relatively uniform. The cytoplasm was fragile and demonstrated a finely fibrillar material. Dense hyaline materials with irregular outline were observed within the loose clusters composed of the tumor cells. The hyaline materials were also observed in the background. Histologic preparation showed spindle cells arranged in a fascicular or storiform pattern. Most eosinophilic globules were distributed between the tumor cells. The globules were positive in periodic acid-Schiff reaction, and were stained blue with Masson's trichrome stain. Immunohistochemically, the tumor cells were strongly and diffusely positive for c-kit, focally and weakly positive for alpha-smooth muscle actin, and negative for CD34 and S-100 protein. We emphasize that skeinoid fibers are characteristic of GIST arising in the small intestine, and their presence predicts a good prognosis, even in malignant GIST.

Gastrointestinal stromal tumors and leiomyosarcomas in the colon: a clinicopathologic, immunohistochemical, and molecular genetic study of 44 cases

Gastrointestinal stromal tumors (GISTs), mesenchymal tumors largely specific for the gastrointestinal tract, have been well defined in the stomach and small intestine, but have not been extensively documented or contrasted with true smooth muscle tumors in the colon. This study was undertaken to determine the clinicopathologic features of GISTs of the colon, excluding the rectum, and to compare them with leiomyosarcomas (LMSs) of the same location. A total of 37 colonic GISTs and seven LMSs from the files of the Armed Forces Institute of Pathology and the Haartman Institute of the University of Helsinki were analyzed. The GISTs occurred predominantly in adults older than 50 years of age (median, 67 yrs), and most were histologically malignant; four small benign tumors (< or = 1 cm) were incidentally detected, and 10 others had minimal mitotic activity (five or fewer mitoses per 50 high-power fields). The colonic GISTs were typically transmural tumors with frequent intraluminal and outward bulging components. Histologically, they usually showed a spindle cell pattern (92%), whereas 8% were epithelioid. Most tumors (19 of 25) were positive for CD117 (KIT) and for CD34 (16 of 27); six tumors coexpressed alpha-smooth muscle actin and CD117; none showed desmin or S-100 protein. C-kit mutations in exon 11 were seen in 5 (36%) of 14 colonic GISTs. None of the patients with incidental small tumors had a recurrence, whereas 2 of 10 patients with tumors larger than 1 cm but minimal mitotic activity died of the disease with liver metastasis. Nearly all patients whose tumor was larger than 1 cm and showed more than five mitoses per 50 high-power fields died of disease; half had evidence of metastasis. LMSs were typically intraluminally bulging, polypoid masses that showed a histologic likeness to differentiated smooth muscle cells. They occurred in five men and two women with a median age of 61 years. Most LMSs were high-grade histologically and showed smooth muscle actin, desmin, or both. All were negative for CD34 and CD117 and lacked c-kit mutations. Five of the seven patients died of disease, and two had a long-term survival, despite high mitotic activity. These results show that KIT-positive GISTs are more common than LMSs of the colon, and these tumor groups have clinicopathologic differences that warrant their separation.

Gastric Stromal Tumor

Gastric stromal tumors display a bewildering array of immunohistological and ultrastructural features as well as variable biological behavior. These tumors are rare as compared with ones that arise from the gastric epithelium. Moreover, they have been the subjects of controversy because of their uncertain histogenesis. We report the pathological features of gastric stromal tumors we recently encountered in three patients.

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.

Esophageal stromal tumors: a clinicopathologic, immunohistochemical, and molecular genetic study of 17 cases and comparison with esophageal leiomyomas and leiomyosarcomas

Although rare elsewhere in the gastrointestinal tract, leiomyomas (LMs) are the most common esophageal mesenchymal neoplasms. In contrast, gastrointestinal stromal tumors (GISTs) predominate in the stomach and intestines but have not been documented in the esophagus. This study was undertaken to determine the clinicopathologic features and frequency of esophageal GISTs compared with LMs and leiomyosarcomas (LMSs) of the esophagus. A total of 68 stromal/smooth muscle tumors from the Armed Forces Institute of Pathology and the Haartman Institute of University of Helsinki were reclassified by current histologic and immunohistochemical criteria. There were 17 GISTs, 48 LMs, and three LMSs. The esophageal GISTs occurred in 12 men and five women with a median age of 63 years (range, 49-75 years). All tumors were from the lowest third of the esophagus, and the most common complaint was dysphagia, whereas two tumors were detected incidentally. Histologically the tumors had an overall basophilic appearance and showed combinations of solid, myxoid, and perivascular collarlike patterns with a spindle cell histology in 13 patients and epithelioid histology in four patients. All tumors were positive for CD117 and for CD34, whereas two patients were also positive for alpha-smooth muscle actin (SMA) and three patients were positive for desmin. One patient showed a unique immunophenotype with coexpression of CD117, CD34, SMA, and desmin. Nine patients died of disease, including all who had a tumor larger than 10 cm, and also one patient whose tumor showed five mitoses per 50 high-power fields. In comparison, esophageal LMs (n = 48) occurred in a younger population (median age, 35 years) but, similar to the GIST group, men predominated (67%). All LMs were clinically indolent tumors with no tumor-related mortality. The LMs showed eosinophilic cytoplasm, and were positive for desmin and SMA, and negative for CD117 and CD34. All three LMSs were large high-grade tumors that showed muscle cell markers but no CD117. All patients died of disease. Esophageal GISTs showed mutations in exon 11 of c-kit as described previously in gastric and intestinal GISTs. The separation of GISTs from esophageal LMs is important diagnostically because the former group has a high risk of malignant behavior.

GASTROINTESTINAL STROMAL TUMOURS

The histogenesis of 10 spindle cell tumors of gastrointestinal tract (GIT) of last three years of our institution was studied, on the basis of immunohistochemical (IHC) staining. The tumours were categorized into benign, borderline malignant and malignant, mainly based on the histologic parameters (HP) such as predominant cell type, cellularity, type of growth pattern, mitotic figures etc. The study included 7 males and 3 females in the age group from 21 to 56 years. 4 tumors were located in stomach and 6 in the small intestine. The initial symptoms included pain abdomen, palpable mass and general weakness. There were 7 benign, 1 borderline and 2 malignant leiomyomatous tumors according to the histologic parameters we followed. Vimentin, desmin, S-100, and non-specific enolase (NSE) were the immunological markers used to identify the cellular lineage. Smooth muscle differentiation was demonstrated by nine (6 benign and 3 malignant) tumours. One male patient (Case 1), originally reported as leiomyoma based on HP, was positive for S-100 and NSE. Another case, a female, categorised as leiomyosarcoma, showed dual differentiation toward myogenic and neural elements on IHC staining (Case 2). IHC study played important role in the identification of cellular differentiation of these tumors as the same was not possible on light microscopic findings alone.

An immunohistochemical and clinicopathological study of gastrointestinal stromal tumors

Immunohistochemical and clinicopathological features of 58 gastrointestinal stromal tumors (GIST) were studied. One occurred in the esophagus, 41 in the stomach, nine in the small intestine, and seven in the large intestine. By using indirect immunoperoxidase staining for Cajal cell markers (c-kit protein and CD34), smooth muscle markers (alpha-smooth muscle actin, desmin, heavy caldesmon and calponin) and Schwann cell markers (S-100 protein and Leu 7), GIST were classified into five groups, such as Cajal cell type (n = 9), myogenic type (n = 5), Schwann cell type (n = 2), mixed cell type (n = 40) and undifferentiated type (n = 2). c-kit Protein (42/58; 72%) and CD34 (45/58; 78%) were commonly and diffusely expressed in GIST. Novel smooth muscle markers, caldesmon (29/58; 50%) and calponin (18/58; 31%), were useful in detecting myogenic characters of GIST. S-100 protein was expressed in 16 (28%) tumors, two of which were also reactive with Leu 7 (CD57). Three small bowel tumors with skeinoid fibers expressed the Cajal cell markers, and were categorizable in GIST. Clinicopathological analyses using aggressive (n = 21) and non-aggressive (n = 21) GIST indicated that the malignant potential was correlated with the intestinal location, large tumor size, high cellularity, necrosis, solid (non-interlacing bundled) pattern of growth, negativity of c-kit protein and/or CD34, high mitotic count, and high MIB-1 labeling.

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

Gastrointestinal stromal tumor or smooth muscle tumor (GIST) is the designation for a major subset of gastrointestinal mesenchymal tumors that histologically, immunohistochemically, and genetically differ from typical leiomyomas, leiomyosarcomas, and schwannomas. Because GISTs, like the interstitial cells of Cajal, the gastrointestinal pacemaker cells, express CD117 (c-kit protein), the origin of GISTs from the interstitial cells of Cajal has been recently proposed. Comparison of GISTs primary in the omentum and mesentery to GISTs primary in the tubular gastrointestinal tract is of particular diagnostic and histogenetic interest in view of the possible similarity of these tumors with the GIST group. In this study, we analyzed 14 omental and 12 mesenteric primary mesenchymal tumors representing smooth muscle tumors or GISTs. These tumors were phenotypically compared with gastric and small intestinal GISTs, leiomyomas of the esophagus, and leiomyosarcomas of the retroperitoneum. Most (13 of 14) omental and mesenteric (10 of 12) tumors showed histologic features similar to GISTs with elongated spindle cells or epithelioid cells with high cellularity; most of these tumors showed low mitotic activity. Omental and mesenteric GISTs were typically positive for CD117 and less consistently for CD34. They often showed alpha-smooth muscle actin reactivity but were virtually negative for desmin and S-100 protein. One omental and two mesenteric tumors showed features of leiomyosarcoma with ovoid, less elongated nuclei, cytoplasmic eosinophilia; all these tumors had significant mitotic activity. These tumors were positive for alpha-smooth muscle actin and two of them for desmin, but all were negative for CD34 and CD117, similar to retroperitoneal leiomyosarcomas. Tumor-related mortality occurred in the group of mesenteric GISTs, but not in the group of omental GISTs. In contrast, all three patients with a true leiomyosarcoma of the omentum or mesentery had documented liver metastases or died of tumor. In summary, we show that tumors phenotypically identical with GISTs occur as primary tumors in the omentum and mesentery. The occurrence of CD117-positive tumors outside the gastrointestinal tract militates against an origin of these tumors exclusively from the interstitial cells of Cajal.

Type VI collagen immunoreactivity in skeinoid fibers in small intestinal stromal tumors

By immunoperoxidase analysis for types I to VI collagen, elastin, cytoskeletal components and some glycoproteins, we found type VI collagen immunoreactivity in amorphous eosinophilic deposits (skeinoid fibers) in three small intestinal stromal tumors. Negative results were obtained for types I, II, III, IV and V collagen, elastin, laminin, ubiquitin, intracellular filaments such as actin, desmin, vimentin, calponin and caldesmon, and glycoprotein such as lysozyme, factor XIIIa, beta2-microglobulin, alpha1-antitrypsin and alpha1-antichymotrypsin. In two lesions, the periodic acid-Schiff-positive skeinoid fibers were also focally labeled for amyloid P component.

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.

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.

Renal angiomyolipoma resembling gastrointestinal stromal tumor with skenoid fibers

We report an unusual case of renal angiomyolipoma occurring in 68-year-old man. The tumor lacked well-developed vascular and adipose components and was composed almost exclusively of smooth muscle cells. Numerous skenoid-like periodic acid-Schiff-positive globules were interspersed between the tumor cells; the lesion therefore closely resembled a low-grade stromal tumor of the gastrointestinal tract. The HMB45-positive/CD34-negative immunophenotype was essential for the diagnosis of angiomyolipoma. Neither gastrointestinal tumor nor any signs of tuberous sclerosis were found. This lesion should be included in the list of morphologic variations of angiomyolipoma, which may cause diagnostic difficulties.

Multiple familial gastrointestinal autonomic nerve tumors and small intestinal neuronal dysplasia

Multiple small intestinal stromal tumors were removed from mother and natural daughter within 15 months of each other. Both had long histories of recurrent iron deficiency anemia and upper gastrointestinal bleeding. Light microscopy revealed that the tumors had arisen in conjunction with diffuse hyperplasia/ dysplasia of Auerbach's myenteric plexus. Immunohistochemistry generally did not show myogenic or paraganglionic phenotypes; CD34 was positive in most tumors. Electron microscopy confirmed the association with the abnormal Auerbach's plexus and showed the structure of gastrointestinal autonomic nerve tumors (GANTs). These findings provide information as to the origin and evolution of GANTs, and also have implications for the clinical management of these tumors which appear to occur more frequently than previously thought.

A primary solitary tumor of the lesser omentum with immunohistochemical features of gastrointestinal stromal tumors

We here present a primary solitary tumor of the lesser omentum that was found in a 71-yr-old woman. Differential diagnosis could not be made preoperatively; therefore, histopathological examination including immunohistochemical studies were performed to determine the nature of the tumor. The resected specimen, measuring 17 cm at the largest point, consisted of the outer solid part and the inner multiloculated cysts. Microscopically, the tumor was characterized by interlacing bundles of elongated spindle cells, with the nuclei focally showing a palisading pattern. However, skeinoid fibers were not observed anywhere. One to three mitoses per 50 high power fields were observed. Immunohistochemically, the tumor was negative for S-100 protein and smooth muscle-specific actin, but stained positive for CD34. The microscopic features were consistent with those of potentially malignant gastrointestinal stromal tumors. Stromal tumors that represent the differentiation toward neither typical leiomyomas or schwannomas rarely occur in the lesser omentum with only one such instance having been reported to date. Due to this rarity, it is difficult to make the differential diagnosis preoperatively, even with existing imaging techniques, and predicting the clinical behavior of such omental tumors is also often difficult. Therefore, complete resection should be performed when such tumors are encountered in daily practice.

Small intestinal stromal tumors: a clinicopathologic study of 31 tumors

The biologic behavior of gastrointestinal stromal tumors is difficult to predict, and they can be best studied in a site-specific fashion. The aims of this study are to analyze the clinicopathologic parameters and assess the prognostic value of p53 (DO-7) and Ki-67 (MIB-1) immunoreactivities in small intestinal stromal tumors (SIST). The histopathologic features of 31 SIST were assessed and categorized into two groups as follows. Group A (clinically aggressive) in which death due to tumor, metastasis, recurrence or relapsed melena were seen (n = 15) and group B (clinically benign; n = 16). For both groups, the period of follow-up was 30-144 months. p53 overexpression was observed in four tumors (31%) in group A, and in none in group B. For groups A and B, the mean Ki-67 index was 16.8 +/- 12.5 and 8.4 +/- 12.6, respectively. Statistical analysis revealed that the significant predictors of malignancy were high cellularity (odds ratio (OR) = 999; 95% confidence interval (CI) = 0-999); p53 overexpression (OR = 999; CI = 0-999); size of tumor > or = 5 cm (OR = 18.0; CI = 1.9-171.9); > or = 5 mitoses/50 high-power fields (HPF) (OR = 17.1; CI = 1.8-165.9); pleomorphism (OR = 17.1; CI = 1.8-165.9); and necrosis (OR = 11.9; CI = 2.2-65.1; P < 0.05). High Ki-67 index (> or = 8.4) had a marginal impact on risk (OR = 4.1; CI = 0.8-20.2; P = 0.08). In conclusion, high cellularity, p53 overexpression, size of tumor > or = 5 cm, > or = 5 mitoses/50 HPF, pleomorphism and necrosis are important parameters for the prediction of malignancy in SIST.

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.

Jejunal stromal tumor with skeinoid fibers or myenteric plexoma: a case report

Small intestinal stromal tumors with 'skeinoid fibers' are uncommon stromal tumors with an associated controversial histogenesis. Although their microscopic appearance is suggestive of a smooth muscle nature, they lack specific smooth muscle features, as evident by electron microscopy and immunohistochemistry. They also appear to lack features of neurogenic origin because they fall to react with neural/neuroendocrine markers such as S-100 protein, neuron-specific enolase and chromogranin. It is interesting, nonetheless, to note that the ultrastructural examination of these tumors may show structures reminiscent of neural differentiation, such as cytoplasmic projections, containing occasional membrane-bound, dense-core, neurosecretory-type granules, which mimick the long cytoplasmic processes seen in tumors of neural origin. Moreover, the association of these tumors with Von Recklinghausen's neurofibromatosis, as well as the presence of 'skeinoid fibers' in proven neurogenic spindle cell neoplasms such as gastrointestinal autonomic nerve tumors and schwannomas, suggests that these tumors might also be neurogenic in origin and enhances the diagnostic value of 'skeinoid fibers' as a possible ultrastructural marker of neural differentiation. Thus, light microscopic evaluation is clearly insufficient to accurately diagnose these tumors and to determine their histogenesis, electron microscopic and immunohistochemical studies being necessary. In this article the histogenesis of small intestinal stromal tumors with 'skeinoid fibers', regarding a jejunal neoplasm in a 63-year-old patient, is reviewed. The light microscopic, immunohistochemical and ultrastructural features are described and compared with findings usually seen in all those stromal tumors which may raise a differential diagnosis, such as smooth muscle stromal tumors, gastrointestinal autonomic nerve tumors, schwannomas, paragangliomas and fibrosarcomas.

Skeinoid fibers in mesectodermal leiomyoma of the ciliary body

Unlike smooth muscle elsewhere in the body, the smooth muscle of the iris and ciliary body is derived from neuroectoderm (mesectoderm). Leiomyomas that arise from the ciliary body, and therefore are of mesectodermal origin, may resemble spindle cell neurogenic tumors by light microscopy. They show positive immunostaining for smooth muscle actin but negative staining for neural markers. Ultrastructurally, the cells have the features of smooth muscle cells. The authors report a typical case of mesectodermal leiomyoma in a 47-year-old woman in which skeinoid fibers, considered to be an ultrastructural marker of neurogenic spindle cell tumors, were frequent together with other ultrastructural features often seen in neuroglial cell tumors. The findings indicate that mesectodermal leiomyoma is unique in its histogenesis as well as in its morphology.

Gastrointestinal autonomic nerve tumors: immunohistochemical and ultrastructural studies in cases of gastrointestinal stromal tumor

The gastrointestinal autonomic nerve tumor (GAN tumor) is an uncommon stromal tumor with a morphological feature resembling the cell processes of the enteric plexus, and was originally termed a plexoma or plexosarcoma. Light microscopic studies show the GAN tumor most often consists of spindle-shaped cells indistinguishable from a smooth muscle tumor or Schwann cell tumor. Immunohistochemical and ultrastructural examinations of 18 cases of gastrointestinal stromal tumor (GIST) were performed. During ultrastructural examination, all of the 12 cases which were immunohistochemically positive for S-100 protein or neuron-specific enolase (NSE) showed synapse-like structures containing dense core neurosecretory granules measuring 100-200 nm, and 40-60 nm endocytoplasmic vesicles. These results suggest that most GIST of neurogenic origin are tumors derived from the myenteric nerve plexus.

Stromal tumors of the jejunum and ileum: a clinicopathologic study of 39 cases

Recently, cell size, cell density, and growth pattern were found to be reliable histologic parameters in separating benign from malignant duodenal stromal tumors. However, there are few data on the histologic features and important prognostic parameters of stromal tumors from other parts of the small bowel. Thus, we studied the clinical and pathologic features of 39 stromal tumors of the jejunum and ileum to determine which parameters would be most useful in distinguishing a benign from a malignant tumor. In all cases, the following histologic parameters were recorded: (a) predominant growth pattern (organoid, fascicular, solid, or mixed), (b) cellularity (low or high), (c) predominant cell type (spindled, epithelioid, or mixed), (d) nuclear pleomorphism (minimal, moderate, or severe), (e) the presence or absence of tumor cell necrosis, (f) the presence or absence of mucosal infiltration, (g) the presence or absence of skeinoid fibers, and (h) the number of mitotic figures per 50 high-power microscopic fields (HPF). Clinical follow-up was obtained in all cases, and the patients were considered to have suffered an adverse outcome if they developed metastatic disease or died as a complication of their tumor. In the absence of these features, patients were not considered to have suffered an adverse outcome. Twenty-five patients suffered an adverse outcome. Twenty-one patients died of disease from 1 month to 9 years (median: 2 years). One patient died at 4 days because of postoperative complications. Three patients were alive with metastatic disease at 6 months, 6 years, and 7 years. Twenty-four of these 25 patients developed metastatic disease, most commonly to the liver. Fourteen patients did not suffer an adverse outcome. Eleven patients were alive without disease from 2 to 11 years (median: 3 years), and three patients died of unrelated causes at 1, 1, and 3 years. Although there was some overlap in features between clinically benign and malignant tumors, features that were significantly associated with an adverse outcome included tumor size > 5 cm, mitotic counts > 5 mitotic figures per 50 HPF, high cellularity, the absence of a predominant organoid growth pattern, the absence of skeinoid fibers, the presence of severe nuclear pleomorphism, and the presence of mucosal infiltration and tumor cell necrosis (p < 0.05 using the chi-square and Fisher's exact tests). Features that were significantly associated with decreased survival included tumor size > 5 cm, mitotic counts > 5 mitotic figures per 50 HPF, high cellularity, the absence of skeinoid fibers, and the presence of tumor cell necrosis (p < 0.05 using the Mantel-Haenszel log-rank test). Given the fact that there is some overlap in these features between clinically benign and malignant tumors, a multiparametric analysis using the above features is the most effective way of predicting clinical behavior.

Gastrointestinal autonomic nerve tumor: further observations regarding an ultrastructural and immunohistochemical analysis of six cases

Gastrointestinal autonomic nerve tumor (GANT) is a specialized form of stromal neoplasm whose ultrastructural features support a myenteric plexus derivation and provide the basis for its diagnosis. GANT actual frequency, relationship to skeinoid fibers, and CD34 expression status are some of the controversial aspects of this entity. Out of 14 gastrointestinal stromal tumors gathered during a 1-year period, six (42%) instances were diagnosed as GANT by electron microscopic study of at least five ultrathin sections per case. Additionally, GANTs were immunohistochemically investigated with a panel of nine antibodies including CD34. Ultrastructurally, every GANT case showed diagnostic findings and evidence of skeinoid fibers, whereas immunohistochemically all except one were CD34 positive. Immunoreactivity for neuron-specific enolase, synaptophysin, and vimentin was a common occurrence as well. In conclusion, GANT seems to be more frequent than hitherto recognized, skenoid fibers are a regular feature of GANT, and a positive CD34 immunoreaction does not discriminate between GANT and other non-smooth muscle, non-schwannian neoplasms.

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.

A case of von Recklinghausen's disease with bilateral pheochromocytoma-malignant peripheral nerve sheath tumors of the adrenal and gastrointestinal autonomic nerve tumors

A 48-year-old man with neurofibromatosis type 1 presented with chest pain, paroxysmal hypertension, tachycardia, and progressive respiratory insufficiency. Clinical investigation displayed calcified tumors in the anterior mediastinum and pararenal region. Histological examination at autopsy revealed composite tumors consisting of pheochromocytoma and malignant peripheral nerve sheath tumor (MPNST) at two sites: the left adrenal gland and the region surrounding the inferior vena cava, probably corresponding to the right adrenal gland. The MPNST component showed a varied histological appearance, including hyalinized bands with polygonal cells, a cartilaginous and myxoid stroma, a hemangiopericytomatous architecture, and a fibrosarcomatous structure, which suggested osteosarcoma, chondrosarcoma, angiosarcoma, and fibrosarcoma, respectively. In addition, based on the ultrastructural findings, the gastrointestinal tract was involved with mesenchymal tumors showing neurogenic differentiation. These lesions suggest the divergent cellular differentiation of neural crest-derived cells to mesenchymal elements as well as neuroectodermal neoplasms.

Gastrointestinal autonomic nerve tumours and their separation from other gastrointestinal stromal tumours: an ultrastructural and immunohistochemical study of seven cases

Gastrointestinal stromal tumours (GIST) represent a heterogeneous group whose classification frequently requires ultrastructural and immunohistochemical studies. In a retrospective study of the ultrastructural findings of 24 gastrointestinal stromal tumours, whose light microscopic study has yielded ambiguous results and in which accurate diagnosis had required ultrastructural support, seven were found to have the characteristics of gastrointestinal autonomic nerve (GAN) tumours. In all of them the diagnosis was based on the presence of dendritic processes with dense neuroendocrine granules. Immunohistochemically, the seven tumours were negative for smooth-muscle markers. All stained positively for vimentin. NSE, chromogranin, and synaptophysin were positive in most of them, while S-100 protein was positive only in two cases. We present the ultrastructural and immunohistochemical features of seven GANT against the background of the GISTs of our series. We conclude that GAN tumours cannot be diagnosed by light microscopy alone but this tumour group displays characteristic electron microscopic and immunohistochemical features and appears to represent a distinct type of GIST.

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.

Gastrointestinal autonomic nerve tumors: a clinicopathological, immunohistochemical and ultrastructural study of 10 cases

Gastrointestinal Autonomic Nerve Tumors (GANTs) are an underrecognized group of gastrointestinal stromal tumors (GISTs) putatively arising from the neural plexuses of the bowel wall. Approximately 24 cases have been previously reported. Their histogenesis, malignant potential, morphology and phenotypic features are not well defined. We present details of 10 GANTs iterating features, predominantly ultrastructural, allowing distinction from other GISTs. Clinical details are: sex-7M, 3F; age range 31-79 yrs, mean 53; symptoms/signs--abdominal pain 3, GI bleeding 3, mass 2, anemia 2. Follow-up ranged from 1-102 mths, mean 29. Seven tumors involved the small intestine and 3 were gastric. Tumor size ranged from 30-160 mm, mean 79. They were solid and cystic, often transmural and usually involved mesentery and retroperitoneum. Spindled and epithelioid cells were "compartmentalized" by a branching microvasculature. Eosinophilic, PAS positive stromal globules were prominent. Paraffin immunostaining results were (number positive/total): vimentin (8/9), NSE (10/10), S100 protein (6/10), neurofilament protein (0/9), synaptophysin (3/9), desmin (2/9, focal), smooth-muscle actin (0/9). Ultrastructural diagnostic features were elaborate, branching cytoplasmic processes containing microtubules, intermediate filaments and varying numbers of neurosecretory granules. Characteristic features were elaborate smooth endoplasmic reticulum enmeshed with intermediate filaments, pleomorphic mitochondria with lamellar cristae, mitochondrial-RER complexes, confronting RER cisternae, and circumscribed collections of stromal "skeinoid" fibres. There were no features of smooth muscle, Schwannian or perineurial differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastrointestinal autonomic nerve tumor presenting as high-grade sarcoma. Case report and review of the literature

Gastrointestinal autonomic nerve (GAN) tumors, also known as plexosarcomas, are a rare distinct subtype of the gastrointestinal stromal tumors. These tumors are usually histologically low-grade, epithelioid or spindle-cell neoplasms that can be distinguished from the other gastrointestinal stromal tumors on the basis of their unique ultrastructural features. A 66-year-old female presented with a histologically high-grade sarcoma of the small bowel. Ultrastructural studies showed features of a GAN tumor. The light microscopic and ultrastructural features are described. The tumor cells gave strong, diffuse staining for vimentin and synaptophysin, and weak focal staining for neuron-specific enolase and S100. While usually presenting as low-grade neoplasms on histologic examination, this case demonstrates that GAN tumors should be considered in the differential diagnosis of a histologically high-grade sarcoma of the gastrointestinal tract, especially when evidence of smooth muscle, peripheral nerve sheath, or neuroblastic origin is not forthcoming.

Multiple benign stromal cell tumours of the small bowel

A rare case of multiple small intestinal stromal cell tumours is described in a 79 year old woman who presented with melaena and anaemia. At surgery, about 40 lesions were noted on the serosal surface of the small intestine, the largest of these tumours being located in the mid-jejunum. This lesion showed central necrosis and haemorrhage with a sinus opening into the jejunal lumen. Histological examination of this jejunal tumour showed epithelioid and spindle shaped cells. A smaller biopsied tumour was a pure spindle cell lesion. Both lesions fitted the criteria for benign stromal cell tumours. Although skenoid fibres were identified, the immunophenotype was characteristically heterogeneous. Multiple benign small intestinal tumours can raise the spectre of metastases when seen at surgery, although their presence in this case does not seem to indicate this.

Small intestinal stromal tumors with skeinoid fibers in neurofibromatosis: report of four cases with ultrastructural study of skeinoid fibers from paraffin blocks

Small intestinal stromal tumors (SIST) with skeinoid fibers (SF) are reported in four patients with neurofibromatosis. SF appeared as intercellular eosinophilic globules that stained positively on periodic acid-Schiff stain and bluish on Masson trichrome stain, like those reported previously. Electron microscopic confirmation of SF was carried out on tissue retrieved from paraffin blocks, which revealed diagnostic ultrastructural features of SF. The association of SIST with SF and neurofibromatosis enhances the diagnostic value of SF as a marker of neurogenic spindle cell tumors. This study also underscores the importance of electron microscopy for differentiation of SF from pseudoskeinoid structures, which may mimic SF on light microscopic examination.

Intracisternal collagen fibrils in proliferative fasciitis and myositis of childhood

During ultrastructural examination of a difficult to diagnose tumor, short spacing collagen fibrils (periodicity of banding, approximately 43.2 nm) and native collagen fibrils (periodicity of banding, approximately 53 nm) were found in dilated and vacuolated cisternae of rough endoplasmic reticulum and the perinuclear cistern. Original diagnoses from several histopathologists included alveolar soft part sarcoma, malignant fibrous histiocytoma, atypical fibroxanthoma, and myogenic tumor. The finding of intracisternal collagen (which is but a variety of intracellular collagen) led to the conclusion that this was a fibroblastic neoplasm. This, plus a review of the histologic findings, led to the diagnosis of proliferative fasciitis and myositis of childhood.