CD117阴性胃肠道间质瘤的临床病理及免疫组织化学研究

目的 探讨免疫组织化学在形态学典型、免疫组织化学CD117阴性胃肠道间质瘤(GIST)诊断中的意义.方法 对10例CD117阴性、形态学典型的GIST进行c-kit基因第9、11、13、17号外显子及血小板源性生长因子受体α(PDGFRA)基因第12和18号外显子的基因检测,同时所有病例均进行CD117、CD34、平滑肌肌动蛋白(SMA)、结蛋白、S-100蛋白、WT-1、DOG-1 的免疫组织化学染色(EnVision法).结果 10例中8例完成c-kit及PDGFRA基因的检测,仅1例有c-kit基因第9号外显子突变,余未发现基因突变.10例CD117阴性的病例9例CD34阳性,2例SMA局灶阳性.结蛋白和S-100蛋白均阴性.DOG1弥漫阳性者5例,1例弥漫弱阳性,2例局灶阳性,2例阴性.4例WT-1弥漫阳性,2例局灶阳性,1例有散在肿瘤细胞阳性,3例阴性.结论 对胃肠道及胃肠道外形态学典型、但CD117阴性的GIST病例,联合应用多种免疫组织化学标记有助于诊断.DOG-1和WT-1可作为补充加入到CD117阴性GIST的诊断中.     

DOG-1在胃肠道间质瘤中的表达及其临床意义

Objective To investigate the expression of DOG-1 in gastrointestinal stromal tumors (GIST)and its diagnostic application.Methods Immunohistochemical EnVision technique was used to assess the expression of DOG-1 in 84 cases of GIST in comparison with CD117 and CD34.Results All 84cases of GIST consisted of variable proportions of spindle and epithelioid tumor cells or iust one type of the tumor cell. The expression rates of DOG-1,CD117 and CD34 were 91.3%(42/46),95.7%(44/46)and 82.6%(38/46),in the group of very low and low risk GIST,and were 100%(38/38),100%(38/38)and 78.9%(30/38),respectively,in the group of moderate and hiish risk GIST. leiomyomas,schwannomas,fibromatosis and normal gastrointestinal mucoca did not express these markers.Moreover, the sensitivity and specificity of DOG-1 in the detection of GIST were similar to those of CD117.without statistical difference(P＞0.05)between the two markers.However,the sensitivity and specificity of DOG-1 detection of moderate and high risk GIsT were significandy higher than those of CD34(P＜0.01).Conclusions DOG-1 is a novel marker of gastrointestinal stromal tumors.It has the sensitivity and specificity hisher than CD34,especially in the detection of moderate and high risk GIST.Combined DOG-1and CD117 immunohistochemistry will likely improve the diagnostic accuracy of GIST.     

DOG-1在胃肠道间质瘤中的表达及其临床意义

目的 探讨DOG-1在胃肠道间质瘤(GIST)中的表达及其临床意义.方法 应用免疫组织化学EnVision法检测DOG-1在84例GIST患者肿瘤组织中的表达,并与CD117、CD34标记进行比较观察.结果 GIST患者手术切除肿瘤组织主要由数量不等的梭形细胞和上皮样细胞组成,两种细胞可按不同比例混合性或单一性组成肿瘤的实体.DOG-1、CD117和CD34在极低度及低度危险性GIST组织中阳性表达率分别为91.3%(42/46)、95.7%(44/46)和82.6%(38/46),在中度及高度危险性GIST组织中其阳性表达率分别为100%(38/38)、100%(38/38)和78.9%(30/38),对照组真性平滑肌瘤、神经鞘瘤、纤维瘤病及正常胃肠道黏膜组织中DOG-1、CD117、CD34均无表达,DOG-1标记GIST的敏感性及特异性与CD117相似,差异无统计学意义(P＞0.05),而标记中度及高度危险性GIST的敏感性与特异性明显高于CD34,其表达差异有统计学意义(P＜0.01).结论 DOG-1是一种新的诊断GIST比较特异的标记,尤其是对中度及高度危险性GIST比CD34有更高的敏感性和特异性.与CD117联合应用将有利于进一步提高GIST的诊断水平.

Abstract：

Objective To investigate the expression of DOG-1 in gastrointestinal stromal tumors (GIST)and its diagnostic application.Methods Immunohistochemical EnVision technique was used to assess the expression of DOG-1 in 84 cases of GIST in comparison with CD117 and CD34.Results All 84cases of GIST consisted of variable proportions of spindle and epithelioid tumor cells or iust one type of the tumor cell. The expression rates of DOG-1,CD117 and CD34 were 91.3%(42/46),95.7%(44/46)and 82.6%(38/46),in the group of very low and low risk GIST,and were 100%(38/38),100%(38/38)and 78.9%(30/38),respectively,in the group of moderate and hiish risk GIST. leiomyomas,schwannomas,fibromatosis and normal gastrointestinal mucoca did not express these markers.Moreover, the sensitivity and specificity of DOG-1 in the detection of GIST were similar to those of CD117.without statistical difference(P＞0.05)between the two markers.However,the sensitivity and specificity of DOG-1 detection of moderate and high risk GIsT were significandy higher than those of CD34(P＜0.01).Conclusions DOG-1 is a novel marker of gastrointestinal stromal tumors.It has the sensitivity and specificity hisher than CD34,especially in the detection of moderate and high risk GIST.Combined DOG-1and CD117 immunohistochemistry will likely improve the diagnostic accuracy of GIST.     

PDGFRA强阳性表达是诊断GIST较为特异性标志

胃肠道间质肿瘤(GIST)是腹腔最常见的间叶性肿瘤,来自于Cajal间质细胞或其前体细胞。大多数GISTs有c-kit癌基因的突变,c-kit(CD117)阳性被认为是诊断GIST的金标准,也是格列为治疗GIST的必要条件。近来研究发现PDGFRA基因突变作为另一个癌变机制可见于部分缺乏c-kit突变的GIST中,然而,PDGFRA免疫组化检测在GIST诊断中的价值还未见报道。作者应用免疫组化方法检测了39例GISTs和20例其它腹腔内间叶性肿瘤中PDGFRA的表达,同时进行了CD117免疫组化染色和PDGFRA和c-kit基因的突变分析。39例GISTs中,胃24例、小肠10例、大…     

CD117阴性的胃肠道间质瘤的超微结构特点及基因突变检测

目的探讨CD117阴性的胃肠道间质瘤（GIST）的超微结构及c-kit和血小板源性生长因子受体A（PDGFRA）基因的突变情况。方法用免疫组织化学方法（EnVision法和SP法）从101例GIST中筛选到6例CD117阴性的GIST,观察了6例CD117阴性的胃肠道间质瘤的电镜变化,用PCR直接测序的方法检测6例CD117阴性的胃肠道间质瘤的c-kit基因外显子9、11、13、17和PDGFRA基因外显子12和18突变。结果电镜下观察到6例GIST的超微结构特点与卡哈尔细胞相似,通过PCR直接测序检测揭示c-kit基因9、11、13和17外显子均无突变,而3例GIST的PDGFRA有突变,其中2例D842V突变,1例R841S突变。结论PDGFRA基因的突变可能是CD117阴性的胃肠道间质瘤发生的重要分子基础。     

肾混合性上皮间质肿瘤和成人囊性肾瘤的临床病理学观察

Objective To study the clinicopathologie features,immunophenotype and differential diagnosis of mixed epithelial and stromal tumor of kidney ( MEST) and adult cystic nephroma ( CN).Methods Five cases of MEST and 4 cases of CN were retrospectively analyzed.Immunohistochemical study was carried out and the literature was reviewed.Results All of the five patients with MEST were females.Their median age was 45 years.For CN,there were 3 males and 1 female and their median age was 41 years.All patients presented with loin pain and hematuria.On gross examination,MEST was well-circumscribed but non-encapsulated.There was no evidence of haemorrhage or necrosis.Three of the cases were solid in nature.One was composed of a mixture of solid and cystic elements,while the remaining case showed a multicystic cut surface bridged by thick fibrous septa.On the other hand,CN were well-circumscribed and encapsulated.They were multiloculated cystic in nature.The cystic spaces were separated by thin septa and there was no significant solid or necrotic component.Histologically,MEST consisted of proliferation of cystically dilated glands admixed with spindly stromal cells with various cellularity and growth patterns.Both the glandular and stromal elements were well-differentiated with no cytologic atypia identified.The glandular structures in 2 of the cases were partially lined by endometrial or tubal epithelium.In contrast,the thin-walled cystic spaces in CN were lined by a single layer of epithelium.Immunohistochemical　study showed that the epithelial cells were positive for pan-cytokeratin and epithelial membrane antigen.The spindle cells in MEST expressed vimentin (5/5 ) ,smooth muscle actin (3/5 ),desmin (4/5 ),CD10 (5/5),estrogen receptor (4/5) and progesterone receptor (4/5).They were negative for HMB45,CD34,CD117 and S-100 protein.On the other hand,the spindle cells in CN were variably positive for vimentin (4/4),smooth muscle actin (4/4),desmin (1/4),estrogen receptor (3/4) and progesterone receptor (1/4).They were negative for CD10,HMB45,CD34,CD117 and S-100 protein.Conclusions Both MEST and CN are uncommon renal neoplasm.Most of them run a benign clinical course.The stromal cells in MEST show smooth muscle or myofibroblastic differentiation.Areas demonstrating Miillerian features also existed in some cases.MEST and CN share overlapping histological and immunohistochemical features,and may represent spectrum of the same group of lesions.     

肾混合性上皮间质肿瘤和成人囊性肾瘤的临床病理学观察

Objective To study the clinicopathologie features,immunophenotype and differential diagnosis of mixed epithelial and stromal tumor of kidney ( MEST) and adult cystic nephroma ( CN).Methods Five cases of MEST and 4 cases of CN were retrospectively analyzed.Immunohistochemical study was carried out and the literature was reviewed.Results All of the five patients with MEST were females.Their median age was 45 years.For CN,there were 3 males and 1 female and their median age was 41 years.All patients presented with loin pain and hematuria.On gross examination,MEST was well-circumscribed but non-encapsulated.There was no evidence of haemorrhage or necrosis.Three of the cases were solid in nature.One was composed of a mixture of solid and cystic elements,while the remaining case showed a multicystic cut surface bridged by thick fibrous septa.On the other hand,CN were well-circumscribed and encapsulated.They were multiloculated cystic in nature.The cystic spaces were separated by thin septa and there was no significant solid or necrotic component.Histologically,MEST consisted of proliferation of cystically dilated glands admixed with spindly stromal cells with various cellularity and growth patterns.Both the glandular and stromal elements were well-differentiated with no cytologic atypia identified.The glandular structures in 2 of the cases were partially lined by endometrial or tubal epithelium.In contrast,the thin-walled cystic spaces in CN were lined by a single layer of epithelium.Immunohistochemical　study showed that the epithelial cells were positive for pan-cytokeratin and epithelial membrane antigen.The spindle cells in MEST expressed vimentin (5/5 ) ,smooth muscle actin (3/5 ),desmin (4/5 ),CD10 (5/5),estrogen receptor (4/5) and progesterone receptor (4/5).They were negative for HMB45,CD34,CD117 and S-100 protein.On the other hand,the spindle cells in CN were variably positive for vimentin (4/4),smooth muscle actin (4/4),desmin (1/4),estrogen receptor (3/4) and progesterone receptor (1/4).They were negative for CD10,HMB45,CD34,CD117 and S-100 protein.Conclusions Both MEST and CN are uncommon renal neoplasm.Most of them run a benign clinical course.The stromal cells in MEST show smooth muscle or myofibroblastic differentiation.Areas demonstrating Miillerian features also existed in some cases.MEST and CN share overlapping histological and immunohistochemical features,and may represent spectrum of the same group of lesions.     

Clinicopathologic features of gastrointestinal stromal tumor with synchronous carcinoma北大核心CSCD

Objective: To evaluate the clinicopathologic features of gastrointestinal stromal tumor (GIST) with synchronous carcinoma and the treatment principle. Methods Nineteen cases of GIST with synchronous carcinoma were collected from 113 cases of CIST from 2002 to 2008. The clinicopathologic features were studied and the expression of CD117, CD34, smooth muscle actin and S-100 protein were detected by immunohistochemistry using EliVision method. The expression of proliferation marker Ki-67 was also studied. CIST with synchronous carcinoma and those without carcinoma were compared. Results: Nineteen cases (16.8%) of GIST with synchronous carcinoma were found, including 11 males and 8 females (male to female ratio 1.38:1. 00). The age of the patients ranged from 43 to 66 years (median age 57 years). Five of 19 cases were located in the inferior segment of esophagus and 14 were in the gastric wall. The diameter ranged from 0. 6 to 3. 8 cm [mean (1.91 ± 0. 92) cm]. Three of 19 cases showed low grade dysplasia, and there was no dysplasia in the remaining 16 cases. The number of mitosis ranged from 0 to 4/50 HPF [mean (0. 74 ± 1. 07)/50 HPF]. The Ki-67 proliferative index (number of Ki-67 positive cell/HPF) ranged from 0 to 7. 72% [mean (2. 51 ±2. 20)%]. The synchronous carcinomas included two esophageal carcinomas and 17 gastric cancers. In contrast, patients of GIST without carcinoma included 52 males and 42 females (male to female ratio 1. 24:1. 00). The age of patients ranged from 43 to 71 years (median age 55 years). Seventy-nine of the 94 cases were located in the stomach, 10 were in the intestine and 5 were in the esophagus. The diameter ranged from 2.4 to 15.5 cm [mean (5. 42 ±6. 17) cm]. Seventy-nine of the 94 cases showed variable degrees of dysplasia, and 12 cases were of high malignant potential. The number of mitosis ranged from 0 to 53/50 HPF [average (3. 78 ± 10. 22)/50 HPF].The Ki-67 proliferative index ranged from 0 to 37.54% [mean (6.78 ± 12. 45) %]. Comparing these two groups, the male to female ratio of GIST with synchronous carcinoma was higher than that of GIST without carcinoma. The average diameter of GIST with synchronous carcinoma was smaller than of those without carcinoma. The number of mitosis and Ki-67 proliferative index of GIST with synchronous carcinoma were significantly lower than those without carcinoma (t' = 2.809, P < 0. 05; t' = 3.095, P < 0. 05, respectively). Conclusions: Sixteen point eight percent of GIST may be associated with synchronous carcinoma. There are no special clinical symptoms in most of GIST with synchronous carcinoma, as these GIST are usually incidental findings. The Ki-67 proliferative index of GIST with synchronous carcinoma is significantly lower than that of GIST without synchronous carcinoma. Most GIST with synchronous carcinoma can be treated by the standard treatment for the accompanying carcinoma, and do not require specific additional treatments.     

肾混合性上皮间质肿瘤和成人囊性肾瘤的临床病理学观察

Objective To study the clinicopathologie features,immunophenotype and differential diagnosis of mixed epithelial and stromal tumor of kidney ( MEST) and adult cystic nephroma ( CN).Methods Five cases of MEST and 4 cases of CN were retrospectively analyzed.Immunohistochemical study was carried out and the literature was reviewed.Results All of the five patients with MEST were females.Their median age was 45 years.For CN,there were 3 males and 1 female and their median age was 41 years.All patients presented with loin pain and hematuria.On gross examination,MEST was well-circumscribed but non-encapsulated.There was no evidence of haemorrhage or necrosis.Three of the cases were solid in nature.One was composed of a mixture of solid and cystic elements,while the remaining case showed a multicystic cut surface bridged by thick fibrous septa.On the other hand,CN were well-circumscribed and encapsulated.They were multiloculated cystic in nature.The cystic spaces were separated by thin septa and there was no significant solid or necrotic component.Histologically,MEST consisted of proliferation of cystically dilated glands admixed with spindly stromal cells with various cellularity and growth patterns.Both the glandular and stromal elements were well-differentiated with no cytologic atypia identified.The glandular structures in 2 of the cases were partially lined by endometrial or tubal epithelium.In contrast,the thin-walled cystic spaces in CN were lined by a single layer of epithelium.Immunohistochemical　study showed that the epithelial cells were positive for pan-cytokeratin and epithelial membrane antigen.The spindle cells in MEST expressed vimentin (5/5 ) ,smooth muscle actin (3/5 ),desmin (4/5 ),CD10 (5/5),estrogen receptor (4/5) and progesterone receptor (4/5).They were negative for HMB45,CD34,CD117 and S-100 protein.On the other hand,the spindle cells in CN were variably positive for vimentin (4/4),smooth muscle actin (4/4),desmin (1/4),estrogen receptor (3/4) and progesterone receptor (1/4).They were negative for CD10,HMB45,CD34,CD117 and S-100 protein.Conclusions Both MEST and CN are uncommon renal neoplasm.Most of them run a benign clinical course.The stromal cells in MEST show smooth muscle or myofibroblastic differentiation.Areas demonstrating Miillerian features also existed in some cases.MEST and CN share overlapping histological and immunohistochemical features,and may represent spectrum of the same group of lesions.     

肾混合性上皮间质肿瘤和成人囊性肾瘤的临床病理学观察

Objective To study the clinicopathologie features,immunophenotype and differential diagnosis of mixed epithelial and stromal tumor of kidney ( MEST) and adult cystic nephroma ( CN).Methods Five cases of MEST and 4 cases of CN were retrospectively analyzed.Immunohistochemical study was carried out and the literature was reviewed.Results All of the five patients with MEST were females.Their median age was 45 years.For CN,there were 3 males and 1 female and their median age was 41 years.All patients presented with loin pain and hematuria.On gross examination,MEST was well-circumscribed but non-encapsulated.There was no evidence of haemorrhage or necrosis.Three of the cases were solid in nature.One was composed of a mixture of solid and cystic elements,while the remaining case showed a multicystic cut surface bridged by thick fibrous septa.On the other hand,CN were well-circumscribed and encapsulated.They were multiloculated cystic in nature.The cystic spaces were separated by thin septa and there was no significant solid or necrotic component.Histologically,MEST consisted of proliferation of cystically dilated glands admixed with spindly stromal cells with various cellularity and growth patterns.Both the glandular and stromal elements were well-differentiated with no cytologic atypia identified.The glandular structures in 2 of the cases were partially lined by endometrial or tubal epithelium.In contrast,the thin-walled cystic spaces in CN were lined by a single layer of epithelium.Immunohistochemical　study showed that the epithelial cells were positive for pan-cytokeratin and epithelial membrane antigen.The spindle cells in MEST expressed vimentin (5/5 ) ,smooth muscle actin (3/5 ),desmin (4/5 ),CD10 (5/5),estrogen receptor (4/5) and progesterone receptor (4/5).They were negative for HMB45,CD34,CD117 and S-100 protein.On the other hand,the spindle cells in CN were variably positive for vimentin (4/4),smooth muscle actin (4/4),desmin (1/4),estrogen receptor (3/4) and progesterone receptor (1/4).They were negative for CD10,HMB45,CD34,CD117 and S-100 protein.Conclusions Both MEST and CN are uncommon renal neoplasm.Most of them run a benign clinical course.The stromal cells in MEST show smooth muscle or myofibroblastic differentiation.Areas demonstrating Miillerian features also existed in some cases.MEST and CN share overlapping histological and immunohistochemical features,and may represent spectrum of the same group of lesions.     

Gastrointestinal stromal tumors (GISTs): CD117, DOG-1 and PKCθ expression. Is there any advantage in using several markers?

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the digestive tract. Expression of CD117, DOG1 and PKCθ was investigated immunohistochemically in a series of 99 paraffin-embedded GISTs in order to determine the sensitivity and diagnostic value of these markers. KIT exons 9, 11, 13 and 17 and PDGFRA exons 12 and 18 were amplified by PCR and sequenced. A total of 94/99 (94%) GISTs stained positive for CD117, 81/99 (82%) for PKCθ and 90/99 (91%) for DOG-1. A significant correlation was noted between CD117 and DOG-1 expression (p=0.0001). All three markers were expressed in 74% (73/99) of GISTs. Of the five CD117-negative cases, two were PKCθ-negative/DOG1-negative and had mutations in KIT exon 11. Two were PKCθ-positive/DOG1-positive and had mutations in PDGFRA (one each in exons 12 and 18), and one was DOG1-negative/PKCθ-positive, with a PDGFRA exon 18 mutation. The most sensitive marker was CD117, followed by DOG-1 and PKCθ. Although PKCθ was less sensitive, and its staining is more challenging and difficult to interpret, the use of this marker is highly recommended, particularly in CD117-negative/DOG-1-negative GISTs.     

Strong PDGFRA positivity is seen in GISTs but not in other intra-abdominal mesenchymal tumors: Immunohistochemical and mutational analyses.

Mutation of the platelet-derived growth factor receptor-alpha (PDGFRA) gene has been well documented as an alternative oncogenic mechanism in a subset of gastrointestinal stromal tumors (GISTs) lacking c-kit mutations. However, the role of PDGFRA immunohistochemistry in the diagnosis of GISTs has not been well studied. We investigated PDGFRA immunoreactivity in GISTs and in other intra-abdominal mesenchymal tumors, and correlated PDGFRA expression with CD117 positivity and with the mutational status of PDGFRA and c-kit genes. In addition, expression of phosphorylated AKT, an activated downstream molecule in the PDGFRA and c-kit signaling pathways, was correlated with PDGFRA and CD117 status. A total of 39 GISTs and 20 other mesenchymal tumors in the abdomen were included in this study. Thirty-five of 39 GIST cases (89.7%) were positive for PDGFRA and 19 of these 35 positive cases were strongly positive. Five of 20 non-GIST lesions (25%) were positive for PDGFRA, but none of these cases were strongly positive. With one exception, PDGFRA-positive cases were also positive for CD117. Phosphorylated AKT positivity was not associated with the immunoreactivity or mutation of PDGFRA and c-kit, suggesting that the activation of AKT is probably independent of the activation of PDGFRA and c-kit in GISTs. Of 14 GISTs assayed, 4 had mutations in c-kit at exons 11 or 17, and 4 had mutations in PDGFRA at exons 12 or 18. Three of 4 GIST cases with PDGFRA mutations show epithelioid morphology and strong PDGFRA immunoreactivity with prominent perinuclear dotlike accentuation (so-called Golgi pattern). In conclusion, strong PDGFRA positivity with Golgi pattern is a useful adjunct in the diagnosis of GISTs with PDGFRA mutation.     

165例胃肠道间质瘤中c-kit和PDGFRA基因突变的检测和临床诊断意义

目的探讨在中国较大样本的胃肠道问质瘤（GIST）中c-kit基因和PDGFRA基因的突变状况,为进一步的生物靶向治疗提供依据。方法用免疫组织化学EnVision法、聚合酶链反应（PCR）扩增和直接测序的方法,检测165例GIST c-kit基因9、11、13和17号外显子突变以及PDGFRA基因12和18号外显子突变。结果病理组织学诊断的165例GIST病例中有155例（94％）免疫组织化学显示CD117阳性。在CD117阳性的GIST中,c-kit基因总突变率为76．1％（118／155）：分别为11号外显子67．1％（104／155）、9号外显子7．1％（11／155）、13号外显子1．3％（2／155）和17号外显子0．6％（1／155）。绝大多数为杂合性突变,少数为纯合性突变。11号外显子的突变位点多集中在5’端的经典热点,其次为3’端的框内串联重复。后者主要以核分裂象少的老年女性胃部病例多见。9号外显子突变代表一类发生在年轻男性体积较大的小肠病变。13号外显子发现一处新的突变点L641P。PDGFRA基因突变见于50％（5／10）CD117阴性病例,均为18号外显子突变,包括常见的D842V点突变和一个框内843-846处IMHD缺失伴有S847T的新突变。PDGFRA基因突变多见于发生在后腹膜／网膜的具有高度侵袭危险性的病例。结论中国GIST病例大多数存在c-kit基因和PDGFRA基因的突变,且在基因突变类型和肿瘤原发部位问有非随机的联系。除了发现几个新的突变形式外,国人的GIST似乎和西方国家有些不同的突变特点。靶向治疗需要基因突变分型的启示和指导。     

High-resolution melting amplicon analysis as a method to detect c-kit and platelet-derived growth factor receptor alpha activating mutations in gastrointestinal stromal tumors

High-resolution melting amplicon analysis (HRMAA) was used to detect c-kit and platelet-derived growth factor receptor alpha (PDGFRA) activating mutations in 96 gastrointestinal stromal tumors (GISTs). HRMAA detected mutations in 87 GISTs (91%). Of the 87 cases, 69 (79%) contained c-kit mutations and 18 (21%), PDGFRA mutations. One c-kit mutation-positive case contained an exon 9 mutation, ins FY at codon 503, that has not been previously described. One PDGFRA mutation-positive case contained mutation D842V del 843, also not previously described. Of 18 PDGFRA mutation-positive cases, 3 (17%) were strongly positive for kit expression as measured by CD117 immunohistochemical analysis. Of 69 c-kit mutation-positive cases, 66 (96%) showed strong kit immunohistochemical expression, but 3 (4%) showed negative to weak CD117 expression. Of 96 cases, 9 (9%) were wild type for c-kit and PDGFRA. Of the wild-type cases, 8 still showed strong immunohistochemical kit expression, whereas 1 showed weak kit expression. GISTs with PDGFRA mutations were found in the stomach, omentum, and peritoneum but not the small intestine. GISTs with c-kit exon 9 mutations were found primarily in the small intestine. HRMAA is a sensitive technique that can be used to rapidly identify c-kit and PDGFRA activating mutations in GISTs.     

Use of tissue microarrays and immunohistochemistry to standardize the diagnosis of gastrointestinal stromal tumors

We assessed the concordance among seven general pathologists with respect to histologic diagnosis and interpretation of c-kit proto-oncogene (KIT) and platelet-derived growth factor receptor alpha (PDGFRA) immunostaining of 36 cases of primary spindle-cell tumor, predominantly of the gastrointestinal tract, mesentery, and retroperitoneum, based on review of a tissue microarray (TMA) subjected to immunohistochemistry with antibodies to KIT/CD117, PDGFRA, vimentin, desmin, smooth muscle action, CD34, and S-100 protein. Tumors included 20 molecularly analyzed gastrointestinal stromal tumors (GISTs), 4 leiomyosarcomas, 4 schwannomas, 4 desmoid-type fibromatoses, and 4 solitary fibrous tumors. The mean overall concordance with original diagnosis for each histologic type was 91.1%, with a mean kappa value of 0.91. With respect to PDGFRA immunostaining, the four GISTs with PDGFRA mutation were interpreted as cytoplasm positive, but the 16 GISTs with c-kit mutation were interpreted as weak or positive. These results indicate that the overall concordance with original diagnosis in mesenchymal tumors with the use of immunohistochemical panels is high, despite the use of TMAs. To some extent, PDGFRA immunophenotyping may be useful in GISTs with PDGFRA mutation, but it was not highly reproducible or specific. Therefore, in KIT-negative or weakly positive GISTs, mutation analysis will be required.     

Extragastrointestinal stromal tumor of the urinary wall bladder: case report and review of the literature

Most mesenchymal tumours of the gastrointestinal tract are now referred to as gastrointestinal stromal tumours (GISTs). These tumours typically express c-kit (CD117) and CD34; 30-50% are (often focally) positive for alpha-smooth muscle actin, and all are negative for desmin and S100 protein. Recently, mutations in exon 11 of the c-kit gene have been identified as a molecular genetic marker for the subset of GISTs. In this report, we describe a mesenchymal tumour removed from the pelvic cavity of a 34-year-old man. The tumour was strongly attached to the external wall of the urinary bladder. The neoplasm grossly resembled a leiomyoma, and was histologically composed of sheets of spindle cells with a dense collagenous background. The mitotic activity was low (less then 1 per 50 high-power fields). Immunohistochemically, tumour cells were negative for alpha-smooth muscle actin and desmin and positive for CD117 and CD34. This case illustrates that tumours which are phenotypically and genotypically similar to GISTs may present in sites other than the tubular gastrointestinal tract.     

Loss of DOG-1 expression associated with shift from spindled to epithelioid morphology in gastric gastrointestinal stromal tumors with KIT and platelet-derived growth factor receptor α mutations

Most gastric gastrointestinal stromal tumors (GISTs) display spindle cell morphology and coexpress CD117 (KIT), DOG-1, and CD34. Secondary loss of DOG-1 has not been reported. We present two gastric GISTs which showed loss of DOG-1 in the epithelioid component but retained its expression in the minor spindle cell component. Patients were a 67-year-old man and an 80-year-old woman with 4.8-cm and 3.5-cm gastric GISTs harboring mutations in KIT exon 11 (c.1729_1758dup30; p.P577_R586dup) and platelet-derived growth factor receptor α (PDGFRA) exon 18 (c.2527_2538del12; p.I843_D846del), respectively. Both were predominantly epithelioid with a minor microscopic spindle cell component (3-12 mm). The spindle cell component was CD117⁺CD34⁺DOG-1⁺ in both cases. The epithelioid component in case 1 was CD117⁺CD34⁺DOG-1^?. In case 2, the epithelioid component strongly expressed PDGFRA (dot-like) but lost CD117, CD34, and DOG-1. These cases confirm the immunophenotypic heterogeneity as secondary events in GIST. Loss of DOG-1 in KIT-negative PDGFRA mutants should not preclude diagnosis.     

Spindle cell tumor of urinary bladder serosa with phenotypic and genotypic features of gastrointestinal stromal tumor

Most mesenchymal tumors of the gastrointestinal tract are now referred to as gastrointestinal stromal tumors (GISTs). The tumors differ from ordinary leiomyomas and schwannomas in several respects: the GISTs typically express c-kit protein (CD117) and CD34, 30% to 50% of them are (often focally) positive for alpha-smooth muscle actin, and all are negative for desmin and S100 protein. Recently, mutations in the exon 11 of the c-kit gene have been identified and confirmed as a molecular genetic marker for the subset of GISTs. In this report, we describe a mesenchymal tumor removed from the pelvic cavity of a 52-year-old woman, who is alive without disease 36 months after the surgery. The 5-cm tumor was densely attached to the external aspect of the urinary bladder but was attached to small intestine by only filmy adhesions. The tumor grossly resembled a leiomyoma and was histologically composed of sheets of spindle cells with a dense collagenous background. The mitotic activity was low, less then 1 per 50 high-power fields. Immunohistochemically, the tumor cells were negative for alpha-smooth muscle actin and desmin and positive for CD117 and CD34. Molecular genetic analysis of the exon 11 of the c-kit gene revealed a point mutation in the region commonly mutated in GISTs. This mutation substituted T for A in the codon 557, leading to the change of amino acid sequence (tryptophan for arginine) of the KIT protein. This case illustrates that tumors phenotypically and genotypically similar to GISTs may present in sites other than the tubular gastrointestinal tract.