Epithelioid variant of gastrointestinal stromal tumor: Diagnosis by fine-needle aspiration

Epithelioid gastrointestinal stromal tumors (GISTs) may cause significant diagnostic confusion on fine-needle aspiration (FNA) with carcinomas, neuroendocrine tumors, and melanoma, particularly when metastatic. This study characterizes the cytologic features of nine cases of epithelioid GISTs that were obtained by computerized tomographic guidance in five, by endoscopic ultrasound in three, and from an excised liver tumor in one. Six cases presented as liver masses, one as a perisplenic mass, one as an abdominal mass, and one as a gastric mass. The aspirates revealed mainly single or small clusters of epithelioid cells with a moderate amount of granular to clear cytoplasm, small uniform nuclei with mild to marked nuclear envelope irregularities. Binucleation and intranuclear inclusions were frequent findings. Collagenous stroma was seen in most cases. In three cases, a neuroendocrine tumor was the initial diagnosis. Immunocytochemical staining for c-kit (CD117) was performed on cellblocks in six cases and was positive in five cases. On the subsequent surgical specimen, CD117 was positive in the c-kit-negative cytology case. The diagnosis of GIST should be considered in aspirates of the gastrointestinal tract, liver, mesentery, or abdominal wall mass lesions when epithelioid cells are the predominant cell type. Ancillary studies such as immunohistochemical stains are usually helpful in making a definitive diagnosis.     

A c-kit-negative gastrointestinal stromal tumor with a platelet-derived growth factor receptor alpha mutation.

Gastrointestinal stromal tumors (GISTs) are well-recognized mesenchymal neoplasms of the intestinal tract. A diagnosis of GIST is not always possible using IHC techniques for detection of c-kit. The authors describe a 64-year-old man who presented with an upper abdominal quadrant mass. Histology showed a predominantly epithelioid neoplasm with focal "spindle cell" areas. IHC studies were positive for muscle markers and negative for c-kit. The morphologic and immunophenotypic appearance could be compatible with either a smooth muscle tumor or a GIST. Because of the differences in treatment protocols and prognosis between these two entities, molecular studies to detect c-kit or platelet-derived growth factor receptor (PDGFR) activating mutations were performed. No mutations were found in the c-kit gene, but a mutation was detected in the PDGFR gene. This additional molecular study allowed the authors to formulate the precise diagnosis of a c-kit-negative GIST with strong smooth muscle marker expression.     

PKCtheta expression in gastrointestinal stromal tumor.

Gastrointestinal stromal tumor is characterized by a gain of function mutation of KIT gene and the expression of c-kit protein, but in 5% of cases, c-kit expression is negative although histological findings of gastrointestinal stromal tumor are most suspicious. The existence of c-kit-negative gastrointestinal stromal tumors points to the need of additional markers for making the diagnosis. In this study, we studied the expression of PKCtheta and correlated their expression with other immunohistochemical profiles of gastrointestinal stromal tumors and evaluated their usability as a diagnostic marker. For this purpose, 220 gastrointestinal stromal tumors were immunohistochemically stained for PKCtheta, c-kit, CD34, alpha-smooth muscle actin and S-100 protein. Additionally, genetic studies of KIT and PDGFRA genes were performed using c-kit-negative or PKCtheta-negative cases. All the 220 masses were either PKCtheta-positive or c-kit-positive. PKCtheta was positive in 212 (96%) cases and c-kit was positive in 216 (98%) cases in the cytoplasm of tumor cells with a diffuse staining pattern. Out of 212 PKCtheta-positive GISTs, 208 (98%) cases were c-kit-positive, 174 (82%) cases were CD34-positive, 62 (29%) cases were SMA-positive and S-100 protein was positive in 54 cases (26%). Genetic analyses on eight PKCtheta-negative cases showed exon 11 mutations of KIT gene in four cases. Two PKCtheta-positive and c-kit-negative GISTs showed mutations of PDGFRA gene. Our study shows that PKCtheta is a useful marker and it may play a role in the development of gastrointestinal stromal tumors. Together with c-kit, PKCtheta immunostaining can be used as an important diagnostic tool in the pathologic diagnosis of gastrointestinal stromal tumors with its high specificity and sensitivity.     

bcl-2和p16在胃肠道间质瘤中的表达及其临床意义

目的 探讨bcl-2和p16的表达与胃肠道间质瘤(gastrointestinal stromal tumor，GIST)的良恶性及发生发展的关系。方法 应用免疫组织化学技术EnVision微波二步法检测40例GIST(良性20例，恶性20例)中bcl-2和p16蛋白的表达。结果 40例GIST中有29例表达bcl-2，23例表达p16，阳性率分别为72．5％和57．5％。bcl-2阳性信号定位于细胞质，p16阳性信号定位于细胞质和细胞核。bcl-2、p16的表达与GIST的良恶性、组织学分型、部位、性别及年龄均无关。结论 bcl-2及p16可能在GIST的早期阶段即参与肿瘤的发生发展，但两者不能作为判断肿瘤良恶性的指标。     

胃肠道间质肿瘤组织发生的探讨

目的探讨胃肠道间质肿瘤（ｇａｓｔｒｏｉｎｔｅｓｔｉｎａｌｓｔｒｏｍａｌｔｕｍｏｒ，ＧＩＳＴ）的组织发生。方法对３６例ＧＩＳＴ进行组织学、组织化学及免疫组织化学观察。结果胃和大肠间质肿瘤呈间叶细胞表型，但光镜下观察到在１５例发生于小肠的梭形细胞肿瘤中，瘤细胞之间存在着嗜酸性小体即丝团样纤维（ｓｋｅｉｎｏｉｄｆｉｂｅｒ，ＳＦ），Ｍａｓｓｏｎ三色染色呈蓝色，ＰＡＳ呈强阳性；免疫组化染色显示Ｓ－１００蛋白阳性率为４４．４４％，ｄｅｓｍｉｎ阳性率为８．３３％，瘤细胞的免疫表达与其分化程度无关。结论胃和大肠的间质肿瘤免疫表型复杂，提示其起源与原始间叶细胞有关，而小肠间质肿瘤大多数为神经源性肿瘤。可能起源于肠壁内在神经丛的神经膜细胞或来自小肠的自律神经。     

PKC theta, a novel immunohistochemical marker for gastrointestinal stromal tumors (GIST), especially useful for identifying KIT-negative tumors

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor in the digestive tract and the majority of GIST has characteristic gain-of-function mutations of the c-kit gene, which encodes the KIT receptor for stem cell factor. The present study aimed to establish the usefulness of protein kinase C theta (PKC theta) as an immunohistochemical marker for GIST in comparison with KIT immunohistochemistry. PKC theta immunohistochemistry was carried out not only on 48 cases of GIST and another 40 cases of gastrointestinal mesenchymal tumors, but also on 24 cases of various tumors known to be immunohistochemically positive for KIT. Immunohistochemically, 41 out of 48 cases (85%) of GIST were positive for PKC theta, and its expression was confirmed by Western blot analysis using six cases of surgically resected GIST. In the present study there were six GIST immunohistochemically negative for KIT, which histologically revealed a myxoid epithelioid appearance characteristic to that of GIST with platelet-derived growth factor receptor alpha mutation. All six GIST were immunohistochemically positive for PKC theta. No PKC theta immunoreactivity was observed in other gastrointestinal mesenchymal tumors and various KIT-positive tumors except for three cases (14%) of gastrointestinal schwannomas. The present study revealed that PKC theta is an immunohistochemically novel and useful marker for GIST, especially for GIST negative for KIT.     

Gastrointestinal stromal tumor of the digestive organs: a histopathologic study of 31 cases in a single Japanese institute

The author herein reports histopathologic features of 31 surgical cases of gastrointestinal stromal tumor (GIST) of the digestive organs. The 31 cases of GIST were diagnosed in our pathology laboratory. They consisted of 24 cases of gastric GIST, 1 case of hepatic GIST, 1 case of small intestinal GIST, 4 cases of colon GIST, and 1 case of rectal GIST. The age of the patients ranged from 56 year to 84 years with a mean of 71 years. Male to female ratio was 21:10. The presenting symptoms were gastrointestinal bleeding in 13 cases, abdominal pain and discomfort in 13 cases, and asymptomatic in 5 cases. Endoscopy and imaging modalities including US, CT and MRI were useful to detect the tumors in all cases, and biopsies confirmed the GIST diagnosis in 21 cases. The size of GIST ranged from 1 cm to 12 cm with a mean of 4.3 cm. Grossly, 23 cases were submucosal tumors, 6 serosa-side tumors, 1 solid tumor in the liver, and 1 rectal polyp. Histologically, 28 cases were of spindle cell type and 3 of epithelioid type. According to mitotic counts and tumor size, the malignant risk was very low in 4 cases, low in 14 cases, intermediate in 9 cases, and high in 4 cases. Immunohistochemically, all cases were positive for KIT and vimentin, 30 cases for CD34, and 4 cases for α-smooth muscle actin. None were positive for desmin and S100 protein. Ki-67 labeling ranged from 2% to 18%. P53 protein was negative in all cases. PDGFRA was positive in 20 cases among 24 cases examined. Genetic analysis using PCR-direct sequencing method was performed in 5 GISTs; all the 5 GISTs showed point mutations or deletions in KIT gene, but did not in PDGFRA gene. The 5 cases of GIST were positive for PDGFRA protein, suggesting that PDGFRA overexpression is not associated with PDGFRA gene mutations. Four of the 31 cases showed metastases. The chemotherapy was imatinib mesylate in 6 cases, and none in 25 cases. Four cases of high risk died of GIST, and 27 cases are alive now without tumors.     

Stromal gastrointestinal tumors in children: about a case

Stromal gastrointestinal tumors or GIST are undifferentiated mesenchymal tumors of gastrointestinal tract that showed characteristic c-kit expression. GIST are very rare in children and only 21 cases are reported in literature. The authors present a GIST arising in the stomach of a 7-year-old girl and revealed by severe anaemia. The patient underwent surgical resection and chemotherapy because of high-risk markers. Positive diagnosis and prognosis of paediatric GIST are discussed with literature data.     

The expression of MDM2 in gastrointestinal stromal tumors: immunohistochemical analysis of 35 cases

Background

Gastrointestinal stromal tumors (GIST) are the most common primary mesenchymal tumors of the digestive system. The assessment of their biological behavior still remains a scientific challenge. To date, there are no well-established biological prognostic markers of GIST. Our aim is to study the expression of the MDM2 oncoprotein in GIST through an immunohistochemical analysis.

Methods

It was a retrospective study of 35 cases of GIST diagnosed from 2009 to 2012 in the department of pathology of Hassan II university hospital, Fès, Morocco. MDM2 immunohistochemical staining was performed on archival paraffin-embedded and formalin-fixed specimens (with a threshold of nuclear positivity >?10%). Analysis of correlations between MDM2 immunoexpression and clinicopathological features of GIST has been performed.

Results

The mean age was 55.23 years (range 25–84 years) with a male predominance (sex ratio?=?1.5). The stomach was the main site of GIST, with 17 cases (48.57%) followed by the small bowel (9 cases, 25.71%). The spindle cell type GIST was the most frequent morphological variant (29 cases, 82.85%). Tumor necrosis was present in 8 cases (22.85%). Two patients (5.71%) had very low risk GIST, 5 (14.28%) had low risk GIST, 7 patients (20%) had intermediate risk tumors. The remaining 21 cases (60%) had high risk GIST. At the time of diagnosis, 9 patients (25.71%) had metastatic tumors. At immunohistochemical analysis, 40% of cases (14 patients) stained positive for MDM2. Of these MDMD2-positive tumors, 11/14 (78.57%) had high risk tumors and 8/14 cases (57.14%) presented with metastatic GIST. MDM2 positivity was significantly associated with the metastatic status (p?=?0.001).

Conclusion

The current study suggests that MDM2 immunohistochemical expression is a negative histoprognostic factor in GIST with a statistically significant correlation with metastasis.

     

Novel V600E BRAF mutations in imatinib-naive and imatinib-resistant gastrointestinal stromal tumors

BRAF and NRAS are commonly mutated in cancer and represent the most frequent genetic events in malignant melanoma. More recently, a subset of melanomas was shown to overexpress KIT and harbor KIT mutations. Although most gastrointestinal stromal tumors (GISTs) exhibit activating mutations in either KIT or PDGFRA, about 10% of the cases lack mutations in these genes. It is our hypothesis following the melanoma model that mutations in BRAF or NRAS may play a role in wild-type GIST pathogenesis. Alterations in RAS/MEK/ERK pathway may also be involved in development of imatinib resistance in GIST, particularly in tumors lacking secondary KIT or PDGFRA mutations. Imatinib-naive wild-type GISTs from 61 patients, including 15 children and 28 imatinib-resistant tumors without secondary KIT mutations were analyzed. Screening for hot spots mutations in BRAF (exons 11 and 15) and NRAS (exons 2 and 3) was performed. A BRAF exon 15 V600E was identified in 3 of 61 GIST patients, who shared similar clinical features, being 49- to 55-years-old females and having their tumors located in the small bowel. The tumors were strongly KIT immunoreactive and had a high risk of malignancy. An identical V600E BRAF mutation was also identified in one of 28 imatinib resistant GIST lacking a defined mechanism of drug resistance. In conclusion, we identified a primary BRAF V600E mutations in 7% of adult GIST patients, lacking KIT/PDGFRA mutations. The BRAF-mutated GISTs show predilection for small bowel location and high risk of malignancy. A secondary V600E BRAF mutation could represent an alternative mechanism of imatinib resistance. Kinase inhibitors targeting BRAF may be effective therapeutic options in this molecular GIST subset.     

Trends in incidence and survival of mesenchymal neoplasm of the digestive tract within a defined population of northern Norway

Population-based incidence and survival data for gastrointestinal stromal tumor (GIST) are sparse due to the fact that GIST is a rather novel entity both clinically and pathologically, and has not been registered as a separate entity in population-based cancer registries. The aim of the present study was to reclassify all mesenchymal tumors within a defined population of northern Norway over a time-span of 30 years with the purpose of estimating trends of incidence and survival. One hundred and forty-one patients with mesenchymal neoplasms of the digestive tract were identified: 102 as GISTs, 32 as leiomyomatous tumors, 4 as schwannomas, and 3 as fibromas. Incidence rates of GIST showed a significant increase over the whole period, which was not observed for the non-GIST cases. Analysis of GIST cases showed that cases with more than 5 mitoses per 50 high power fields had an increased expected mortality 4 times that of those with fewer mitoses, and the combination of mitotic count and size of tumor can be recommended for categorizing the tumors into different risk levels. The study confirms that GIST is by far the most frequent mesenchymal neoplasm of the digestive tract and that the incidence has increased over the last 30 years.     

Gastrointestinale Stromatumoren des Magens

Gastrointestinal stromal tumors (GIST) are the most frequent mesenchymal tumors of the gastrointestinal tract. Two thirds of them are located in the stomach, another 30% occur in the small bowel, while the remaining tumors occur in the rectum or more rarely in the oesophagus. GIST most commonly grow from the smooth muscular layer towards the serosal surface whereas development towards to the mucosal layer is less frequent. In the latter case ulceration may occur, leading to gastrointestinal bleeding as the main symptom. However, the majority of GIST of the stomach are asymptomatic, resulting in large tumors on initial diagnosis. Most gastric GIST are not visible on endoscopy but may be diagnosed by endosonography. Due to their location in the outer layers of the tubular gastrointestinal tract biopsy is often hindered of even impossible. GIST of the stomach differ from tumors in other locations with regard to their morphology, molecular pathology and prognosis. This present article provides an overview of these differences also with regard to possible therapeutic consequences.     

Collision tumor of the esophagus: report of a case with mixed squamous cell carcinoma and gastrointestinal stromal tumor

Esophageal cancer is mainly divided into squamous cell carcinoma and adenocarcinoma. Epidemiologically, the former contributes to 90% of worldwide esophageal cancer cases, while adenocarcinoma contributes to two-thirds of cases in developed countries. Although other rare types and collision with multiple histological types of tumors do occur in the esophagus, it is very rare for a gastrointestinal stromal tumor (GIST) to collide with an epithelial malignant tumor. To date, only three cases have been reported in the literature. The current study reported a 69-year-old male patient with squamous cell carcinoma and GIST in the middle esophagus. There was no merging of tissue components between these tumors. This study together with a literature review indicates that esophageal collision tumors have been increasingly reported in recent years. Histology and immunohistochemistry are needed to make a differential diagnosis. The exact oncogenic mechanism or the interaction of two independent neoplasms still remains to be determined, and further investigation, such as electron microscopy and genetic analysis, may help to elucidate the pathogenesis of the colliding tumors.     

胃肠间质瘤28例诊治分析

目的 探讨胃肠间质瘤(GIST)的临床诊断、治疗和预后.方法 回顾性分析南开医院2002年1月至2007年9月收治的胃肠间质瘤28例临床资料及其肿瘤组织病理切片免疫组化结果 .结果 肿瘤部位以胃肠为主,本组均行手术治疗.术后病理诊断10例良性,18例为潜在恶性和恶性;免疫组化CD34阳性19例(67.9%),CD117阳性28例(100%),抗平滑肌抗体(SMA)阳性13例(46.4%),而S-100阳性1例(3.6%).胃间质瘤中CD34表达率在良性肿瘤与恶性肿瘤之间以及交界性肿瘤与恶性肿瘤之间表达差异有显著性意义(P＜0.05).术后随访:良性GIST 10例,平均随访时间25.6个月,8例无局部复发、转移;2例术后1年内复发再手术;恶性GIST 18例,平均随访18.5个月,9例局部复发再手术,5例肝肺转移,4例死亡.结论 CDM可能在胃间质瘤的发生、发展过程中发挥了重要作用.手术完全切除对于GIST是主要的治疗方法 .肿瘤大小及核分裂像数目是GIST重要的预后因素.     

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: definition, histological, immunohistochemical, and molecular features, and diagnostic strategy

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

Imatinib Plasma Monitoring-Guided Dose Modification for Managing Imatinib-Related Toxicities in Gastrointestinal Stromal Tumor Patients

Imatinib, the first-line treatment in patients with advanced gastrointestinal stromal tumors (GIST), is generally well tolerated, although some patients have difficulty tolerating the standard dose of 400 mg/day. Adjusting imatinib dosage by plasma level monitoring may facilitate management of patients who experience intolerable toxicities due to overexposure to the drug. We present two cases of advanced GIST patients in whom we managed imatinib-related toxicities through dose modifications guided by imatinib plasma level monitoring. Imatinib blood level testing may be a promising approach for fine-tuning imatinib dosage for better tolerability and optimal clinical outcomes in patients with advanced GIST.     

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

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

胃肠、泌尿、会阴部间质瘤临床病理及免疫组织化学分析

目的 探讨胃肠道间质瘤(GIST)与胃肠道外GIST型间质瘤的组织学起源与病理特征。方法 对46例胃肠道及13例泌尿道、会阴部原诊断平滑肌瘤、平滑肌肉瘤、许旺瘤的病例作回顾性研究,观察其病理特点,应用免疫组织化学方法观察4种抗体(CD117、CD34、平滑肌肌动蛋白、S—100)的表达,对发生于不同部位的间质瘤进行对比分析。结果 45例为GIST组,CD117阳性表达率为93．3％,CD34阳性率88．9％;12例为胃肠道外GIST型间质瘤组,CDll7阳性表达率为83．3％,CD34阳性率75．0％;2例(其中1例为胃肠道)平滑肌瘤组,CDll7和CD34均为阴性,平滑肌肌动蛋白瘤细胞呈弥漫性强阳性表达。结论 CDll7和CD34标记阳性是确诊间质瘤最具有诊断价值的依据。推测GIST和胃肠道外GIST型间质瘤均系起源于一种非定向分化的、原始间充质干细胞。     

29例上皮样胃肠间质瘤的临床病理特征

目的:探讨29例上皮样胃肠间质瘤(gastrointestinal stromal tumors,GIST)的组织学形态和免疫组织化学特点以及诊断和鉴别诊断,对临床正确诊断治疗和判断预后具有十分重要的临床意义.方法:回顾性分析安阳市肿瘤医院病理科2009年月3月至2016年8月321例完整切除GIST标本,经筛查并重新阅片诊断上皮样GIST 29例.结果:29例上皮样GIST,发生胃部15例,小肠2例,肠系膜3例,直肠4例,腹腔3例,腹膜后1例,盆腔1例.恶性GIST 25例,良性4例.瘤细胞丰富,胞质嗜酸或透明,部分瘤细胞核质比高,核大小不等具有多形性,核分裂较多,可伴有多灶凝固性坏死,间质多数伴有黏液样变性.组织结构形成器官样、片状、巢状及腺泡状等.免疫组织化学CD34,DOG-1在上皮样GIST均弥漫阳性(阳性率100%),CD117阳性率(86%).结论:上皮样GIST发生部位广泛,形态多变,易误诊其他上皮样分化的肿瘤;免疫组织化学CD34,DOG-1,CD117在上皮样GIST诊断及鉴别诊断中具有重要价值;如肿物较大、细胞丰富、核分裂多、间质黏液样变性;绝大多数要考虑恶性GIST.