Imaging of gastrointestinal stromal tumours with modern ultrasound techniques - a pictorial essay.

Gastrointestinal stromal tumours (GIST) are rare tumours of the gastrointestinal tract. Dealing with these tumours requires a profound knowledge of the nature of the lesions and their malignant potentials. Modern ultrasound techniques provide the necessary tools to give the clinician the information he needs to diagnose and treat the patient. This article reviews the actual pathophysiological knowledge of GIST and provides a broad spectrum of ultrasound findings to introduce the reader into modern ultrasound investigation methods of subepithelial tumours. It covers the transcutaneous as well as the endoscopic ultrasound approach. Different conditions of GIST like the low risk or high risk form as well as the metastatic form will be discussed in diagnosis and treatment with plenty of examples. Special attention is paid to contrast-enhanced ultrasound techniques and elastography from the transcutaneous as well as the endoscopic route. Other diagnostic methods like CT, MRI and PET CT are additionally reviewed and their role in clinical practice is compared with that of ultrasound. The aim of the article is to introduce the reader into the new ultrasound techniques and special diagnostic behaviour of GIST and outline clinical pathways to deal correctly with different stages of the disease.

EWS-CREB1: a recurrent variant fusion in clear cell sarcoma--association with gastrointestinal location and absence of melanocytic differentiation.

PURPOSE: Clear cell sarcoma (CCS) usually arises in the lower extremities of young adults and is typically associated with a t(12;22) translocation resulting in the fusion of EWS (EWSR1) with ATF1, a gene encoding a member of the cyclic AMP-responsive element binding protein (CREB) family of transcription factors. CCS arising in the gastrointestinal tract is rare and its pathologic and molecular features are not well defined. EXPERIMENTAL DESIGN: We report a novel variant fusion of EWS to CREB1, a gene at 2q32 encoding another CREB family member highly related to ATF1, detected in three women with gastrointestinal CCS. All three cases contained an identical EWS-CREB1 fusion transcript that was shown by reverse transcription-PCR. In two of the cases tested, EWS gene rearrangement was also confirmed by fluorescence in situ hybridization and the EWS-CREB1 genomic junction fragments were isolated by long-range DNA PCR. RESULTS: Morphologically, all three tumors lacked melanin pigmentation. By immunohistochemistry, there was a strong and diffuse S100 protein reactivity, whereas all melanocytic markers were negative. Ultrastructurally, two of the cases lacked melanosomes. The melanocyte-specific transcript of MITF was absent in two cases, and only weakly expressed in the third case. The Affymetrix gene expression data available in one case showed lower expression of the melanocytic genes MITF, TYR, and TYRP1, compared with four EWS-ATF1-positive CCSs of non-gastrointestinal origin. CONCLUSIONS: EWS-CREB1 may define a novel subset of CCS that occurs preferentially in the gastrointestinal tract and shows little or no melanocytic differentiation. Thus, evidence of melanocytic lineage or differentiation is not a necessary feature of sarcomas with gene fusions involving CREB family members.

Gastrointestinal stromal tumors with prominent myxoid matrix. Clinicopathologic, immunohistochemical, and ultrastructural study of nine cases of a distinctive morphologic variant of myogenic stromal tumor.

Nine cases are presented of a distinctive morphologic variant of myogenic gastrointestinal stromal tumor characterized by an unusually prominent myxoid stromal background reminiscent of a neural neoplasm but lacking the immunohistochemical or ultrastructural features of peripheral nerve sheath or ganglionic differentiation. The patients included six women and three men aged 42 to 86 years (mean, 70). The lesions occurred in the stomach (seven cases) and small intestine (two cases) and ranged in size from 2.5 to 9.5 cm. They were described grossly as well circumscribed, unencapsulated, with a prominently myxoid and often cystic cut surface. Histologically, the lesions were composed of a proliferation of round, spindle, or stellate cells embedded in an abundant myxoid stroma. Histochemical stains showed strong positive reaction of the myxoid stromal background with alcian blue at pH 2.5; this staining reaction was abolished by treatment with hyaluronidase, indicating an abundance of connective tissue mucosubstances rich in hyaluronic acid. Immunohistochemical stains showed strong positivity of the tumor cells with vimentin antibodies in all cases and focal weak to moderate positive staining with muscle actin (HHF35) in eight cases and with desmin in two. Stains for keratin, S-100; epithelial membrane antigen, and collagen type IV were uniformly negative. Ultrastructural examination carried out in all cases showed features consistent with those previously described for myogenic gastrointestinal stromal tumors, namely, scattered mitochondria and prominent Golgi apparati, strands of rough endoplasmic reticulum, focal accumulation of intracytoplasmic microfilaments with occasional focal condensations, subplasmalemmal attachment plaques and immature cell junctions, focal extracellular basal lamina material, and surface-oriented micropinocytotic activity. The myxoid changes observed in these tumors may represent a secondary, nonspecific reaction pattern of the tumor cells to some noxious stimulus, or they may be a form of degenerative phenomenon such as that commonly observed in smooth-muscle tumors of the uterus and other sites. Myogenic gastrointestinal stromal tumors with prominent myxoid stroma should be distinguished from benign schwannoma of the stomach and gastrointestinal autonomic nerve tumors. Because of the differences in prognosis for these entities, immunohistochemical and ultrastructural examinations are recommended for the evaluation of gastrointestinal stromal neoplasms with prominent myxoid features.

Carcinoid tumors and the mixed (composite) glandular-endocrine cell carcinomas.

Carcinoid tumors display a wider histologic spectrum than was previously thought. Some tumors may show atypical features such as glandular profiles, a spindle cell pattern, squamous or osteoid metaplasia, or pleomorphism. In rare cases they may be poorly differentiated and resemble undifferentiated carcinoma or lymphoma. As is well known, some carcinoids are associated with well-defined syndromes, such as the carcinoid or the Zollinger-Ellison syndrome, due to the secretion of amines or peptides. Immunohistochemical analysis of these tumors, however, has shown that whereas one amine or peptide may predominate, most are multihormonal. These findings are also seen with the clinically silent tumors such as the foregut and hindgut carcinoids. Furthermore, the immunohistochemically demonstrated amines and peptides in the primary tumor do not necessarily correspond to those normally found in the overlying endocrine cells. An increasing number of tumors have recently been described which contain an admixture of neoplastic endocrine and nonendocrine epithelial cells. Thus, the classification of gut mucosal tumors into carcinomas and endocrine tumors has had to be modified to include those tumors which have been designated as mixed or composite tumors. These have been further subdivided into several distinctive histologic types. Some of these tumors, such as the microglandular-goblet cell carcinomas, have a distinctive clinical behavior, whereas others, such as the adenoendocrine cell carcinomas, appear to behave in a manner similar to adenocarcinoma. Additionally, there is another tumor type, namely the amphicrine tumor, which differs from the mixed tumors in that endocrine and epithelial cell constituents are present within the same cell.

Gastrointestinal autonomic nerve tumors. A clinicopathological, immunohistochemical, and ultrastructural study of 12 cases.

The gastrointestinal autonomic nerve tumor (GAN tumor) is an uncommon stromal tumor of the intestinal tract and retroperitoneum first described by Herrera and associates in 1984. Distinction of GAN tumors from other gastrointestinal stromal tumors is based on electron microscopic findings. Thus far there have been 12 reported cases. We present an additional 12 GAN tumors, identified by us during 4 years. There were seven male and five female patients and they ranged in age from 10 to 85 years (mean: 58 years). Sites of the tumors were stomach (three), jejunum (two), ileum (four), mesentery (one), and retroperitoneum (two). Eight of the tumors measured > 10 cm in greatest dimension. Usually well circumscribed, the neoplasms were tan to light pink, sometimes hemorrhagic, and soft. There was a variety of histologic patterns including fascicles, palisades, and whorls. Mitotic activity varied from 0 to 23 mitosis per 10 high-power fields (HPF). Using a panel of 10 immunohistochemical stains, only vimentin was consistently positive. There was neuron-specific enolase reactivity in six and S-100 protein reactivity in two cases. All muscle markers were negative. Ultrastructural studies showed neuron-like cells with long axonic cytoplasmic processes ending in bulbous synapse-like structures containing dense-core neurosecretory granules and clear vesicles. Basement membrane was absent. These features are reminiscent of ganglia of the intestinal autonomic nervous system. The patients were followed for 5-125 months (mean of 26 months). Tumor recurred or metastasized to the liver in seven patients (58%) and four patients died with tumor. There were correlations between tumor size (> 10 cm), mitotic count (at least five per 10 HPF), and aggressive behavior.

Leiomyoblastomas and their relationship to other smooth-muscle tumors of the gastrointestinal tract. An electron-microscopic study.

Twelve cases of gastrointestinal leiomyoblastoma were studied by electron microscopy, and the findings were compared with those in 12 cases of leiomyoma and nine cases of leiomyosarcoma of the gastrointestinal tract. All of the "classic" ultrastructural features of smooth-muscle tumors, including subplasmalemmal dense patches, pinocytotic vesicles, cytoplasmic microfilaments and dense bodies, and focal basement membrane formation, were present in the leiomyoblastomas ; however, extensive sampling was commonly necessary to demonstrate such findings. In contrast, these features were more prominent in leiomyomas and leiomyosarcomas.

Neuroectodermal differentiation of the gastrointestinal tumors in the Carney triad. An ultrastructural and immunohistochemical study.

A 16-year-old female with mediastinal paraganglioma and multicentric gastroduodenal "leiomyoblastomas" was thought to have an incomplete form of the Carney triad. The histologic, ultrastructural, and immunohistochemical findings of the gastroduodenal tumors revealed features of neuroectodermal differentiation. The architecture of the smallest duodenal tumors suggested an origin from the myenteric autonomic ganglia.

Malignant mesothelioma: ultrastructural distinction from adenocarcinoma.

Mesotheliomas and metastatic adenocarcinomas involving the pleura are frequently difficult to distinguish by light-microscopic and histochemical methods. In a double-blind study, we have compared ultrastructural features of 10 mesotheliomas of epithelial type and 10 adenocarcinomas from the lung, breast, and upper GI tract, i.e., sites known to give rise to metastases which mimic mesothelioma. Mesotheliomas were observed to have a significantly greater microvillus length/diameter ratio (LDR) than adenocarcinomas (p less than 0.01) and more abundant intermediate filaments (p less than 0.001). Mesotheliomas had more complex microvilli than adenocarcinomas, whereas adenocarcinomas had rootlets (2/10 cases) and lamellar inclusion bodies (2/10 cases), both of which were absent in the mesotheliomas. This study provides quantitative and qualitative ultrastructural features of potential utility in the differential diagnosis of pleural mesotheliomas and adenocarcinomas.

Peptide YY immunoreactive cells in gastrointestinal carcinoids: immunohistochemical and ultrastructural studies of 60 tumors.

The distribution and frequency of peptide YY (PYY) cells in 60 gastrointestinal carcinoids and in the nonneoplastic mucosa around the carcinoids were studied by an indirect immunoperoxidase method with anti-PYY serum. Additionally, the endocrine cell type of the PYY cells in appendiceal and rectal carcinoids was assessed by transmission electron microscopy. A few PYY cells were present in specimens of nonneoplastic mucosa from stomach, duodenum, jejunum, ileum, and appendix, with an abundance of these cells in rectal mucosa. Peptide YY cells were found in one of 13 gastric, one of 13 duodenal, one of one jejunal, zero of two ileal, three of 11 appendiceal, and 16 of 20 rectal carcinoids. All but one of the PYY-positive carcinoids were argyrophil carcinoids. Peptide YY cells in the gastric, duodenal, and jujunal carcinoids were present in small numbers. The three PYY-positive carcinoids of the appendix were composed almost totally of PYY cells, whereas those of the rectum generally contained only sporadic PYY cells. The peptide YY cells observed ultrastructurally contained almost round secretory granules (about 160 nm in average diameter), which were most consistent with D1(H) cell type granules with respect to shape and average diameter. This is the first systematic immunohistochemical and ultrastructural study of PYY cells in gastrointestinal carcinoids.

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.

Solitary solid stromal gastrointestinal tumors in von Recklinghausen's disease with minimal smooth muscle differentiation.

Neurofibromatosis (von Recklinghausen's disease) is occasionally associated with large, solid stromal tumors of the gastrointestinal tract. The authors examined by electron microscopy two such cases of cellular spindle cell neoplasms of the small bowel histologically that resembled leiomyomas, in an attempt to clarify the cell of origin of these lesions. Ultrastructurally, the tumor cells predominantly contained moderate to large numbers of intracellular filaments, small cell processes, discontinuous adherent dense basement-membrane-like material, and abundant intercellular collagen. Definite fusiform dense bodies or structures highly suggestive of them and pinocytotic vesicles were seen in rare cells of each lesion after viewing multiple blocks. While patients with neurofibromatosis are certainly at risk of developing gastrointestinal Schwann cell neoplasms, these two cases suggest that they are also at risk for developing poorly differentiated stromal tumors, resembling leiomyomas by light microscopy, which may show only characteristic cytoplasmic differentiation of smooth muscle cells after ultrastructural examination of many sections.

Crystalloid formation in gastrointestinal schwannoma.

We found intracytoplasmic crystalloids in two of six cases (33.3%) of gastrointestinal (GI) schwannomas. The crystalloid inclusions were periodic acid-Schiff (PAS) positive with diastase-resistance and stained blue with Masson's trichrome. They were needle-shaped and about 1 to 15 microm in length at microscopic levels. They had varying electron density revealed by electron microscopy and some of them showed distinct lattice structure with periodicity of about 9 nm. Survey of soft tissue schwannomas (n = 20) and S-100-negative GI stromal tumors (n = 41) did not detect such crystalloids. Although the origin and differentiation of GI stromal tumors (GISTs) have been a source of controversy, these intracytoplasmic crystalloids may be a marker for Schwann cell differentiation in some GIST.

Expression of microtubule-associated protein tau by gastrointestinal stromal tumors.

The purpose of this work was to study the expression in gastrointestinal stromal tumors (GISTs) of various antigens, including the protein tau associated with enteric neuronal differentiation; to compare their expression with that of c-kit, known to be associated with interstitial cell of Cajal differentiation; and to correlate their expression with the observation of ultrastructural features of gastrointestinal autonomic nerve tumors. Twenty-six GISTs of the stomach and 16 GISTs of the small bowel were included in the study group. Thirty-five tumors served as controls. Tissue sections were immunostained with vimentin, CD34, desmin, specific smooth muscle actin, S100 protein, neuron-specific enolase, PGP9.5, neurofilament, bcl-2 oncoprotein, synaptophysin, chromogranin A, c-kit, and tau. Twenty-one of these tumors were also analyzed ultrastructurally. Of the 42 GISTs, 28 were predominantly spindled, 7 were predominantly epithelioid, and 7 were a mixture of epithelioid and spindle cells. Ten primary GISTs were classified as benign, 9 as borderline, and 23 as malignant. Metastatic dissemination was present at primary surgery in 1 case and eventually developed in 6 patients. Six disease-related deaths were counted. In normal submucous and myenteric plexuses of stomach and small bowel, ganglion cell bodies and nerve fibers strongly expressed tau. Twenty (76.9%) GISTs of the stomach and 12 (75%) of the small bowel expressed tau. Tau often showed intense, diffuse staining patterns in both spindled and epithelioid tumors. Ten (100%) of the 10 benign GISTs, 7 (77.8%) of the borderline GISTs, and 15 (65.2%) of the 23 frankly malignant GISTs expressed tau. Thirty-six GISTs expressed at least 2 different neuronal markers. A coexpression of the neuronal markers and c-kit was observed in 90% of GISTs. The expression of tau was observed in 12 of the 15 GISTs with dense core granules, considered as the definitive finding for a diagnosis of gastrointestinal autonomic nerve tumors. Ten of these also expressed c-kit; 9 were malignant. Tau also immunostained other intra-abdominal tumors, including neuroendocrine carcinomas, paragangliomas and desmoplastic round cell tumors. This immunohistochemical study shows that GISTs are specific tumors of the digestive tract and are nearly always characterized by simultaneous neuronal and interstitial cell of Cajal differentiation. Although the loss of tau expression is observed only in borderline and malignant tumors, its prognostic value is not clear cut.

Role of electron microscopy in the evaluation of soft tissue neoplasms, with emphasis on spindle cell and pleomorphic tumors.

The current significant role of transmission electron microscopy in the evaluation of soft tissue tumors when correlated with conventional histological and immunohistochemical studies is discussed for the following entities: myxofibrosarcoma, storiform-pleomorphic fibrosarcoma (malignant fibrous histiocytoma), and myofibrosarcoma; dermatofibrosarcoma protuberans; hemangiopericytoma; monophasic synovial sarcoma; extrarenal rhabdoid tumor; soft tissue perineurioma; and gastrointestinal stromal tumors, notably the so-called autonomic nerve variant.

Lysozyme localization in normal and diseased human gastric and colonic mucosa. A correlative histochemical, immunohistochemical and immunoelectron microscopic investigation.

The distribution of lysozyme in normal and pathological human gastric and colonic mucosa was studied by light and electron microscopic immunocytochemical techniques and compared with histological and histochemical features. Lysozyme was localized in pyloric glandular epithelial cells, mucous neck cells of fundic glands, Paneth cells and some crypt cells of the mature colonic mucosa. In addition, lysozyme was detected in a large spectrum of "immature" or "regenerative" epithelium: neck cells of the gastric regenerative zone, undifferentiated columnar cells of surface and hyperplastic interfoveolar crests of the stomach, regenerative cells in a healed gastric ulcer, some goblet cells in incomplete intestinal metaplasia, cells of the regenerative zone at the bottom of colonic crypts and, finally, fetal intestinal epithelium. Electron microscopically, we localized lysozyme in the central core of mucous granules in the pyloric gastric glandular epithelium and in the dense mucous granules in gastric mucous neck cells. Lysozyme was also detected in some immature mucin-producing cells of the gastric regenerative zone and in the rough endoplasmic reticulum of surface hyperplastic columnar gastric cells. At the electron microscopic level, a peculiar correlation between the immunopattern of lysozyme and the morphology of mucous granules has been postulated. All our data support and extend the view that the presence of lysozyme may be related to cell immaturity as well as to a regenerative state of the cell. Finally, the lysozyme distribution and its relation to mucosubstances in gastric and colonic carcinoma suggest that lysozyme should not be considered an exclusive marker of cells of gastric derivation.

The Cronkhite-Canada syndrome: an ultrastructural study of pathogenesis.

Electron microscopical and cytochemical studies of intestinal biopsies from a patient with typical features of the Cronkhite-Canada syndrome show that the primary process affects the crypts. This results in cystic dilatation associated with expansion and focal degeneration of the crypt compartment of the intestinal epithelium. The villous epithelium compartment is reduced but ultrastructurally normal. Inflammation and oedema of the lamina propria follows from leakage of mucin through breaks in the abnormal crypts.

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.

GANT-like gastrointestinal pacemaker cell tumours with oncocytic features.

We describe two cases of gastrointestinal stromal tumours with prominent oncocytic features. Both had features consistent with differentiation towards the interstitial cells of Cajal (CC). They were composed of nests and bundles of cells with abundant, deeply granular, eosinophilic cytoplasm. Immunohistochemical investigations revealed positivity with c-kit, vimentin and CD34 antibodies in both neoplasms. Ultrastructurally the neoplastic cells showed characteristic features of CC; they had synapse-like structures and dense core cytoplasmic granules. Oncocytic features were confirmed by immunohistochemistry using anti-mitochondrion antibody in both cases and by electron microscopy in one case (case 1). Although the CC are frequently described as mitochondrion-rich cells, oncocytic changes have not previously been reported as a feature of gastrointestinal autonomic nerve tumour (GANT)-like stromal tumours.