DOG1 Antibody in the Differential Diagnosis of Gastrointestinal Stromal Tumors: A Study of 1840 Cases

Endoscopic ultrasonography-guided diagnosis of subepithelial tumors

Subepithelial lesions are frequently discovered during routine endoscopic examinations. These lesions represent a wide spectrum of heterogeneous benign to malignant conditions. Most of these lesions are asymptomatic. There is no consensus regarding how to manage these lesions. Over the last 2 decades, the approach to these lesions has significantly improved owing to the introduction of endoscopic ultrasonography, fine-needle aspiration, immunohistochemical staining methods, and different treatment options. This article discusses the nature of subepithelial lesions, focusing on the most recent developments that use endoscopic ultrasonography to diagnose and manage these lesions.

Gastrointestinal stromal tumours can express CD10 and epithelial membrane antigen but not oestrogen receptor or HMB45

AIMS

Gastrointestinal stromal tumour (GIST) may share morphological and/or immunohistochemical features with various intra-abdominal neoplasms, including endometrial stromal sarcoma, perivascular epithelioid cell tumour (PEComa), melanoma and synovial sarcoma. Each of these various neoplasms has characteristic immunohistochemical markers, including epithelial membrane antigen (EMA), CD10, oestrogen receptor alpha (ERa) and/or HMB45, and therefore the primary aim of this study was to determine whether these markers are also expressed by GISTs.

METHODS AND RESULTS

Standard size sections of 52 GISTs were immunostained for EMA, CD10, ERa and a melanoma marker cocktail (targeting HMB45 and melan-A). Ten GISTs (19%) showed CD10 immunopositivity. This positivity was confined almost completely to small intestinal GISTs, and was seen among spindle cell GISTs but not epithelioid or mixed cell-type GISTs. Five of the 52 GISTs (9.6%) showed EMA immunopositivity. This positivity was always focal and usually seen in a perivascular location. None of the GISTs showed immunopositivity for ERa or the melanoma marker cocktail.

CONCLUSIONS

GISTs occasionally show CD10 immunopositivity (especially small intestinal spindle cell GISTs), and infrequently show focal EMA positivity. GISTs do not show immunopositivity for ERa or HMB45.

Small intestine gastrointestinal stromal tumors

PURPOSE OF REVIEW

To review the contemporary management of gastrointestinal stromal tumor (GIST), including endoscopy, surgery, and systemic therapy, highlighting the aspects unique to small intestinal tumors.

RECENT FINDINGS

Tumor size, mitotic count, and site of origin are the three key prognostic factors, with mitotic count being the single strongest predictor of recurrence. Tumors arising in the small bowel have worse prognosis than those of comparable size and mitotic count arising in other organs. Endoscopy and endoscopic ultrasound-guided, fine-needle aspiration are key components in the diagnosis of GIST. The role of endoscopy in surveillance and resection remain investigational. Surgery, either open or laparoscopic, remains the only curative option, but recurrence rates are high. Adjuvant therapy with imatinib mesylate improves recurrence-free survival rates and may improve overall survival (OS) with longer duration of treatment. Neoadjuvant imatinib may play an important role in the management of patients with locally advanced disease. For patients with advanced disease, first-line imatinib and second-line sunitinib malate have improved progression-free and OS rates. Systemic treatment should be continued life-long or until treatment failure.

SUMMARY

Advances in the last decade have dramatically changed the management and prognosis of patients with primary and advanced GIST.

Discovered on gastrointestinal stromal tumour 1 (DOG1): a useful immunohistochemical marker for diagnosing chondroblastoma

AIMS

  Cellular areas of chondroblastoma are composed of polygonal chondroblasts with indented nuclei and scattered osteoclast-type multinucleated cells. To learn more about the phenotype of chondroblasts, we investigated the expression of several established immunohistochemical markers in chondroblastomas.

METHODS AND RESULTS

  Nine chondroblastomas were analysed using immunohistochemical antibodies [CD34, α-smooth muscle actin (α-SMA), DOG1, CD117, AE1/AE3 and CD163]. Ten chondromyxoid fibromas, seven giant cell tumours of bone and four foetal proximal femurs were also analysed. The cellular areas of each chondroblastoma contained nests of DOG1(+) αSMA(+) CD117(-) CD34(-) chondroblasts, a phenotype that was not detected in chondromyxoid fibroma cases or in giant cell tumours. Although AE1/AE3 was expressed in all chondroblastomas, the staining intensity and proportion of the positive cells varied widely. Intra-lesional CD163(+) macrophages were detected in all cases of chondroblastoma, chondromyxoid fibroma and giant cell tumours.

CONCLUSIONS

  Our results demonstrated nests of membranous DOG1(+) chondroblasts located within cellular portions of chondroblastoma containing diffuse heterogeneous infiltrates of mostly DOG1(-) chondroblasts, CD163(+) macrophages and multinucleated osteoclastic giant cells. Thus, chondroblastoma can be added to the tumours that are usually positive for DOG1, alongside gastrointestinal stromal tumour (GIST), rare solid-pseudopapillary neoplasms of the pancreas and exceptional mesenchymal tumours including uterine type retroperitoneal leiomyoma, peritoneal leiomyomatosis and synovial sarcoma.

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.

Prognostic factors for survival post surgery for patients with gastrointestinal stromal tumors

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms located in the alimentary tract. Our aim was to assess the influence of prognostic factors on survival in patients surgically treated for GISTs.

STUDY

One hundred and five patients treated between January 1989 and December 2008 were available for study. A retrospective analysis of prognostic factors (age, gender, mitotic index, tumor location, tumor size, risk of malignant behavior, and coexisting other neoplasm) was performed. Univariate and multivariate survival analyses were undertaken.

RESULTS

Univariate analyses revealed the importance of patient gender (p = 0.007), disease location (p = 0.055), mitotic index (p = 0.054) and coexistence with other neoplasms (p = 0.004). However, multivariate analysis showed 3 independently statistically significant factors: coexistence with other neoplasm (RR = 3.53, p = 0.004), male gender (RR = 2.60, p = 0.011) and mitotic index ≥10/50 HPF, (RR = 2.60, p = 0.042).

CONCLUSIONS

Our study has shown that male gender, a high mitotic index ≥10/50 HPF, and coexistence with other malignant neoplasms were independent poor prognostic factors in patients with GIST. The presence of middle or lower gut disease location leads to an increased risk of mortality when compared with the upper gut.

Ano1 as a regulator of proliferation

Ano1 is a recently discovered Ca(2+)-activated Cl(-) channel expressed on interstitial cells of Cajal (ICC) that has been implicated in slow-wave activity in the gut. However, Ano1 is expressed on all classes of ICC, even those that do not contribute to generation of the slow wave, suggesting that Ano1 may have an alternate function in these cells. Ano1 is also highly expressed in gastrointestinal stromal tumors. Mice lacking Ano1 had fewer proliferating ICC in whole mount preparations and in culture, raising the possibility that Ano1 is involved in proliferation. Cl(-) channel blockers decreased proliferation in cells expressing Ano1, including primary cultures of ICC and in the pancreatic cancer-derived cell line, CFPAC-1. Cl(-) channel blockers had a reduced effect on Ano1(-/-) cultures, confirming that the blockers are acting on Ano1. Ki67 immunoreactivity, 5-ethynyl-2'-deoxyuridine incorporation, and cell-cycle analysis of cells grown in low-Cl(-) media showed fewer proliferating cells than in cultures grown in regular medium. We confirmed that mice lacking Ano1 had less phosphorylated retinoblastoma protein compared with controls. These data led us to conclude that Ano1 regulates proliferation at the G(1)/S transition of the cell cycle and may play a role in tumorigenesis.

Gastrointestinal stromal tumor: advances in diagnosis and management

CONTEXT

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract and should be differentiated from other mesenchymal tumors. They harbor specific activating mutations in the KIT or platelet-derived growth factor receptor α ( PDGFRA ) receptor tyrosine kinases, which makes them responsive to pharmacologic inhibitors, such as imatinib mesylate and sunitinib malate.

OBJECTIVES

To provide a comprehensive review of the pathogenesis of GIST and the underlying principles of targeted therapy, to review the salient histologic and immunohistochemical features that facilitate the distinction of GIST from other mesenchymal neoplasms of the gastrointestinal tract, and to present the prognostic parameters for risk stratification that guide clinical management.

DATA SOURCES

Review of the English literature through PubMed as well as personal experience. Photographs were taken from cases encountered at the Cleveland Clinic.

CONCLUSIONS

The discovery of the KIT -GIST connection has not only improved the diagnostic accuracy of GISTs but also provided us with a better understanding of the histogenesis and molecular pathogenesis of these neoplasms.

The management of gastrointestinal stromal tumors: a model for targeted and multidisciplinary therapy of malignancy

Gastrointestinal stromal tumor (GIST) has become a model for targeted therapy in cancer. The vast majority of GISTs contain an activating mutation in either the KIT or platelet-derived growth factor A (PDGFRA) gene. GIST is highly responsive to several selective tyrosine kinase inhibitors. In fact, this cancer has been converted to a chronic disease in some patients. Considerable progress has been made recently in our understanding of the natural history and molecular biology of GIST, risk stratification, and drug resistance. Despite the efficacy of targeted therapy, though, surgery remains the only curative primary treatment and cures >50% of GIST patients who present with localized disease. Adjuvant therapy with imatinib prolongs recurrence-free survival and may improve overall survival. Combined or sequential use of tyrosine kinase inhibitors with other agents following tumor molecular subtyping is an attractive next step in the management of GIST.

Gastrointestinal stromal tumor markers in cutaneous melanomas: relationship to prognostic factors and outcome

Melanoma expresses c-kit, a gastrointestinal stromal tumor marker, but has not been extensively evaluated for protein kinase C θ (PKCθ) or DOG1, and these stains have not been correlated with prognostic factors. We immunostained 62 primary cutaneous and 15 metastatic melanomas for polyclonal c-kit (pc-kit), monoclonal c-kit (mc-kit), PKCθ, and DOG1 and correlated results with prognostic parameters and survival. Of the cutaneous melanomas, 34 (55%) stained for pc-kit, 30 (48%) for mc-kit, 11 (18%) for PKCθ, and 2 (3%) for DOG1. The Breslow depth was 1.00 mm or less in 21 (68%) of 31 pc-kit+ cutaneous melanomas compared with 7 (27%) of 26 pc-kit- melanomas (P = .002). The pc-kit+ melanomas had less nodal disease (1/31 [3%] vs 9/25 [36%]; P = .001) and local recurrence (1/33 [3%] vs 6/27 [22%]; P = .021) but no statistically significant difference in the rate of distant metastases (13/32 [41%] vs 14/27 [52%]; P = .388) or survival (10/34 [29%] vs 16/39 [41%]; P = .301). We found that pc-kit correlates better with prognostic parameters than does mc-kit.

Gastrointestinal stromal tumours--an update for histopathologists

This review aims to summarize recent knowledge gained about gastrointestinal stromal tumour (GIST) of particular relevance to histopathologists. KIT and PDGFRA mutation analyses can be useful for confirming a diagnosis of GIST, but there are some diagnostic limitations to these analyses, and so immunohistochemical markers currently remain crucial to the diagnostic process. Of these markers, CD117 and Discovered on GIST 1 (DOG1) are currently the most sensitive and specific markers of GIST, and recent data appear to disprove the fear that antigen retrieval causes false-positive CD117 immunostaining. The accurate prognostication of GIST has been greatly helped by the National Institutes of Health (NIH) and Armed Forces Institute of Pathology (AFIP) classification systems, although both systems still have limitations, and the behaviours of certain GIST subgroups are less well predicted by both systems. KIT and PDGFRA mutation analyses can help to predict the response of GISTs to receptor tyrosine kinase inhibitors, and both GISTs that respond and those that show resistance to these inhibitors may show characteristic pathological changes. Some GIST subgroups (e.g. Carney syndrome and paediatric GISTs) have had recently described clinicopathological and/or molecular characteristics which may help with the diagnosis and/or treatment of these specific neoplasms.

DOG1 and PKC-θ are useful in the diagnosis of KIT-negative gastrointestinal stromal tumors

Pathological diagnosis of gastrointestinal stromal tumors (GISTs) is based on histological findings and immunohistochemical demonstration of the KIT protein. KIT-negative GISTs account for ∼5% of cases and cause diagnostic difficulties. In the era of imatinib therapy, a correct diagnosis of GISTs is important for therapeutic reasons regardless of KIT expression. Recently, DOG1 has been introduced as an important diagnostic marker with high sensitivity and specificity. In this study, immunohistochemical staining for DOG1 and protein kinase C-θ (PKC-θ) in whole tissue sections, and mutation analyses for KIT and PDGFRA were performed in 26 KIT-negative GISTs. Tissue microarrays of 112 KIT-positive GISTs were used as controls. Overall, 25 KIT-negative GISTs were located in the stomach, and 1 in the rectum. The histological subtype was spindle in 12, epithelioid in 11, and mixed in 3 cases. The expression of DOG1 and PKC-θ was positive in 24 (92%) and in 25 cases (96%), respectively. All 26 KIT-negative GISTs expressed either DOG1 or PKC-θ, and 23 cases (89%) were positive for both makers. PKC-θ was positive in two cases (8%), which lacked both KIT and DOG1 expressions. Mutation analysis showed PDGFRA exon 18 mutation in 15 cases (58%) and KIT exon 11 mutation in 1 case (4%), whereas the remaining 10 cases (39%) were wild type for both KIT and PDGFRA. The expression of DOG1 and PKC-θ showed no significant difference in KIT-negative and KIT-positive GISTs (P=1.000 and P=0.167, respectively). Our findings suggest that both DOG1 and PKC-θ can be used in the diagnosis of KIT-negative GISTs and they show positive staining even in KIT-negative tumors, which are wild type for KIT and PDGFRA on mutation analysis.

Expression of DOG1, CD117 and PDGFRA in gastrointestinal stromal tumors

AIM: To investigate the significance of expression of discovered on GIST-1 (DOG1), CD117 and platelet-derived growth factor receptor alpha (PDGFRA) in gastrointestinal stromal tumors (GISTs) by analyzing their correlation with clinicopathologic features and risk degree of GISTs.

METHODS: The expression of DOG1, CD117 and PDGFRA was detected by immunohistochemistry in 63 cases of GISTs and 43 cases of non-GISTs. The correlation of expression of DOG1, CD117 and PDGFRA with clinicopathologic factors and risk degree of GISTs was then analyzed.

RESULTS: The positive expression rates of DOG1, CD117 and PDGFRA in GISTs were 84.13% (53/63), 90.48% (57/63) and 3.17% (33/63), respectively. The positive expression rates of DOG1 and CD117 in GISTs were significantly higher than that of PDGFRA (both P < 0.01). Of six CD117-negative cases, all were positive for DOG1 and five positive for PDGFRA. The positive expression rates of DOG1, CD117 and PDGFRA in patients with non-GISTs were 11.63%, 16.28% and 6.98%, respectively. The expression of DOG1 and PDGFRA had no significant association with gender, age, tumor location, tumor size, mitotic phase, histotype, or risk degree, while the expression of CD117 was related with tumor location and histotyoe (P = 0.008, 0.045). Tumors derived from the mesentery, abdominal cavity and epiploon had higher positive rates of CD117 than those derived from the stomach, small intestine, colon and rectum (50.00% vs 94.74%, P = 0.008). CD117 was highly expressed in spindle-cell and epithelial-cell types.

CONCLUSION: Both DOG1 and CD117 are highly expressed in GISTs and can serve as specific diagnostic markers for GISTs. DOG1 has a good sensitivity and specificity in the diagnosis of GISTs, especially KIT-negative GISTs. Detection of DOG1, CD117 and PDGFRA expression can not be used for assessing the risk degree of GISTs.

DOG1 antibody is a highly sensitive and specific marker for gastrointestinal stromal tumors in cytology cell blocks

Initial diagnosis of submucosal gastrointestinal stromal tumors (GISTs) is often made from material obtained by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). Although 95% of GISTs are positive for KIT by immunohistochemical analysis on surgical specimens, we have observed several cases of GIST that were negative for KIT on the cell block but subsequently positive on the surgical resection. DOG1 has been found to be a specific and sensitive marker for GISTs on surgical material. We compared KIT and DOG1 staining in 52 GIST cell blocks and in 44 cell blocks of other intra-abdominal spindle cell neoplasms. We found that DOG1 was the more sensitive marker, with positivity in all 52 GIST cell blocks. KIT was positive in 46 (88%) of the GIST cases, with sensitivity dependent on the FNA method. Both markers were highly specific: KIT was negative in all 44 non-GIST cases, whereas DOG1 showed weak positivity in only 1 leiomyosarcoma.

Gastrointestinal stromal tumors: the histology report

Gastrointestinal stromal tumors (GISTs) represent a mesenchymal neoplasm occurring primarily in the gastrointestinal tract, and showing differentiation toward the interstitial cell of Cajal. Its incidence is approximately 15 case/100,000/year. Stomach and small bowel are the most frequently affected anatomic sites. GIST represents a morphological, immunophenotypical and molecular distinct entity, the recognition of which has profound therapeutic implications. In fact, they have shown an exquisite sensitivity to treatment with the tyrosine kinase inhibitor imatinib. Diagnosis relies upon morphology along with immunodetection of KIT and/or DOG1. When dealing with KIT negative cases, molecular analysis of KIT/PDGFRA genes may help in confirming diagnosis. Molecular evaluation of both genes are in any case recommended as mutational status provides key predictive information. Pathologists also play a key role in providing an estimation of the risk of biological aggressiveness, which is currently based on anatomic location of the tumor, size, and mitotic activity.

Gastrointestinal Mesenchymal Neoplasms other than Gastrointestinal Stromal Tumors: Focusing on Their Molecular Aspects

Gastrointestinal (GI) mesenchymal tumors other than gastrointestinal stromal tumor (GIST) are rare neoplasms, but they often enter the differential diagnosis of more common GI lesions. Some of these mesenchymal tumors in the GI tract have well understood molecular pathologic aspects, including desmoid tumors, inflammatory myofibroblastic tumor (IMT), clear cell sarcoma (CCS), inflammatory fibroid polyp (IFP), and synovial sarcoma (SS). Molecular pathology is fast becoming a mainstream focus in laboratories because it aids in the precise classification of tumors, may be prognostic, and may help predict response to therapy. The following review is not intended as an exhaustive summary of all mesenchymal tumors that have been reported to involve the GI tract, but instead will highlight the current knowledge of the most important non-GIST GI mesenchymal neoplasms, focusing on those tumors with well-characterized molecular pathology and how the molecular pathologic features impact current diagnostic, therapeutic, and prognostic standards.

A decade of tyrosine kinase inhibitor therapy: Historical and current perspectives on targeted therapy for GIST

The introduction of molecularly targeted therapies has ushered in a considerable transformation in the management of gastrointestinal stromal tumors (GIST) that currently defines the paradigm of targeted therapy for solid tumors. Indeed, in the past decade the management of GIST has evolved from a disease only effectively treatable by surgery to the archetype of a tumor treatable with a molecularly targeted therapy. Better understanding of the molecular and genetic characteristics that underlie the aberrant behavior of GIST has increased the accuracy of its diagnosis and allowed for the identification of distinct genetic hallmarks, prognostic groups, and treatment strategies. Collectively, this has resulted in the development of the targeted tyrosine kinase inhibitors (TKIs) imatinib and sunitinib, and continues to prompt studies of novel agents in this disease. Since approval in 2002, imatinib has been shown to provide a high level of clinical efficacy in patients with advanced GIST, including a median progression-free survival (PFS) of 2 years and median overall survival approaching 5 years, with some patients progression-free after 10 years of treatment. Imatinib is now also approved in adult patients following resection of KIT-positive GIST. In 2006, sunitinib was approved for the treatment of advanced GIST after failure of imatinib. Sunitinib provides significant benefit in this setting, with a median PFS close to 6 months after imatinib failure. Following progression on these agents, patients have limited treatment options. This critical unmet need is being addressed by the development of new TKIs and the use of novel regimens with approved agents.

Specificity of DOG1 (K9 clone) and protein kinase C theta (clone 27) as immunohistochemical markers of gastrointestinal stromal tumour

AIMS

DOG1 and protein kinase C (PKC) theta are both sensitive immunohistochemical markers of gastrointestinal stromal tumour (GIST). However, there are conflicting data regarding the specificity of the most commonly used PKC theta antibody (clone 27), and there are no existing data regarding the specificity of the only known commercially available DOG1 antibody (K9 clone) at the time of writing. This study's aim was to characterize the immunoreactivity patterns of both monoclonal antibodies amongst a wide range of neoplasm types including, in particular, histological mimics of GIST.

METHODS AND RESULTS

Immunohistochemistry for DOG1 and PKC theta was performed on whole tissue sections from 23 different neoplasm types (total of 125 cases). Ten of these neoplasm types showed CD117 immunopositivity. Only three (Ewing's sarcoma, glomus tumour and synovial sarcoma) of the 23 neoplasm types showed DOG1 immunopositivity, and such positivity was often focal and weak in intensity. In contrast, all but four (ganglioneuromas, leiomyomas, desmoplastic small round cell tumours and PEComa/angiomyolipomas) of the 23 neoplasm types showed PKC theta immunopositivity.

CONCLUSIONS

Compared with CD117, DOG1 (using the K9 antibody) is a more specific marker, whereas PKC theta (using the clone 27 antibody) is a considerably less specific immunohistochemical marker for GIST.

DOG1 and CD117 are the antibodies of choice in the diagnosis of gastrointestinal stromal tumours

AIMS

The histopathological diagnosis of gastrointestinal stromal tumours (GIST) is typically made based on a combination of clinical and morphological features supported by immunohistochemistry studies. The aim of this study was to examine the staining quality, sensitivity, specificity and utility of antibodies used commonly in GIST diagnosis.

METHODS AND RESULTS

Immunohistochemistry with a panel of antibodies [CD117, DOG1, protein kinase C (PKC)-theta, nestin, CD34, smooth muscle actin (SMA), desmin, S100 and CD171] was performed on whole sections from 187 GIST and 29 gastrointestinal mesenchymal tumours, and on several microarrays including 355 GISTs and 120 soft tissue sarcomas. Results showed that DOG1 and CD117 were the most sensitive and specific antibodies used in GIST diagnosis. PKC-theta and nestin were sensitive, but less specific, also staining other spindle cell tumours commonly considered in the differential diagnosis of GIST. CD34 staining was less sensitive than many of the other antibodies and of limited aid in diagnosis. The smooth muscle markers SMA and desmin, together with the neural marker S100, were unhelpful in confirming a diagnosis of GIST, but were particularly useful in the exclusion/diagnosis of other gastrointestinal mesenchymal tumour types.

CONCLUSIONS

In the majority of histologically suspected GISTs a combination of CD117 and DOG1 immunostaining is sufficient to confirm the histological diagnosis.

DOG1 for the diagnosis of gastrointestinal stromal tumor (GIST): Comparison between 2 different antibodies

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. Discovered on GIST-1 (DOG1) is a recently described protein expressed in GISTs irrespective of mutation status. The aim of this study was to investigate the immunohistochemical expression of DOG1 using 2 different monoclonal antibodies (DOG1.1 and the commercially available K9 antibody) in 668 GIST cases and to compare the results with the expression of KIT. DOG1 and KIT expression also were studied in most human normal tissues and several nonmesenchymal and mesenchymal tumors other than GIST. KIT was expressed in 643 (96.3%) GISTs. DOG1.1 and K9 were positive in 538 (80.5%) and 642 (96.1%) GIST cases, respectively. In 25 (3.7%) KIT-negative GIST cases, DOG1 was expressed in 5 (20.0%) and 19 (76.0%) using DOG1.1 and K9 antibodies, respectively. Only 0.9% of GISTs were negative for KIT, DOG1.1, and K9. Most normal human tissues did not reveal KIT and DOG1 expression. DOG1.1 was positive in only 2 of 57 synovial sarcomas and 1 of 61 soft tissue leiomyosarcomas. K9 was positive in 5 of 57 synovial sarcomas, 1 of 14 angiosarcomas, 1 of 61 soft tissue leiomyosarcomas, 3 of 4 adenoid cystic carcinomas of the head and neck, and in myoepithelial cells of 9 of 11 fibroadenomas of the breast. In conclusion, the commercially available K9 is of great utility for the diagnosis of most KIT-negative GISTs, and the combination of both KIT and K9 antibody in a panel of immunohistochemistry can define the diagnosis of GIST in more than 99% of cases.

The use of immunohistochemistry in the diagnosis of metastatic clear cell renal cell carcinoma: a review of PAX-8, PAX-2, hKIM-1, RCCma, and CD10

The diagnosis of metastatic clear cell renal cell carcinoma may be difficult in some cases, particularly in the small image-guided biopsies that are becoming more common. As targeted therapies for renal cell carcinoma are now standard treatment, the recognition and diagnosis of renal cell carcinoma has become even more critical. Many adjunctive immunohistochemical markers of renal epithelial lineage such as CD10 and RCCma have been proposed as aids in the diagnosis of metastatic renal cell carcinoma, but low specificities often limit their utility. More recently described markers (PAX-2, PAX-8, human kidney injury molecule-1, hepatocyte nuclear factor-1-β, and carbonic anhydrase-IX) offer the potential for greater sensitivity and specificity in this diagnostic setting; however, knowledge of their expected staining in other neoplasms and tissues is critical for appropriate use. In this review, we discuss the most widely used immunohistochemical markers of renal lineage with an emphasis on their sensitivity and specificity for metastatic clear cell renal cell carcinoma. Subsequently, we present a variety of organ-specific differential diagnostic scenarios in which metastatic clear cell renal cell carcinoma might be considered and we propose immunopanels for use in each situation.

Clear cell sarcoma of tendons and aponeuroses, and osteoclast-rich tumour of the gastrointestinal tract with features resembling clear cell sarcoma of soft parts: a review and update

Clear cell sarcoma (CCS) is a rare, distinctive soft tissue neoplasm, typically occurring in the distal extremities of young adult patients. Although CCS shows melanocytic differentiation, it is now clear that it is clinicopathologically and genetically distinct from conventional malignant melanoma. The 'osteoclast-rich tumour of the gastrointestinal tract with features resembling clear cell sarcoma of soft parts' is an extraordinarily rare gastrointestinal neoplasm that shares some features of CCS, but differs from it in other ways. The historical, histopathological, ultrastructural, immunohistochemical and genetic aspects of these two tumours are reviewed in this article.

Expression profiling in soft tissue sarcomas with emphasis on synovial sarcoma, gastrointestinal stromal tumor, and leiomyosarcoma

Sarcomas are defined as malignant neoplasms derived from mesenchymal tissues. A variety of different molecular approaches, including gene expression profiling, have identified candidate biomarkers and insights into sarcoma biology that will aid in the diagnosis and treatment of these tumors. Many gene expression profiling findings have been translated into immunohistochemical tests for diagnostic, prognostic, or predictive purposes. This review details gene expression studies done in 3 sarcomas, synovial sarcoma, gastrointestinal stromal tumor, and leiomyosarcoma.

NCCN Task Force report: update on the management of patients with gastrointestinal stromal tumors

The standard of care for managing patients with gastrointestinal stromal tumors (GISTs) rapidly changed after the introduction of effective molecularly targeted therapies involving tyrosine kinase inhibitors (TKIs), such as imatinib mesylate and sunitinib malate. A better understanding of the molecular characteristics of GISTs have improved the diagnostic accuracy and led to the discovery of novel immunomarkers and new mechanisms of resistance to TKI therapy, which in turn have resulted in the development of novel treatment strategies. To address these issues, the NCCN organized a task force consisting of a multidisciplinary panel of experts in the fields of medical oncology, surgical oncology, molecular diagnostics, and pathology to discuss the recent advances, identify areas of future research, and recommend an optimal approach to care for patients with GIST at all stages of disease. The task force met for the first time in October 2003 and again in December 2006 and October 2009. This supplement describes the recent developments in the field of GIST as discussed at the October 2009 meeting.

Primary extragastrointestinal stromal tumor of the pleura: report of a unique case with genetic confirmation

Gastrointestinal stromal tumors (GISTs), the most common mesenchymal neoplasms of the tubular gastrointestinal tract, usually originate in the wall of the stomach or small intestine. Most GISTs harbor oncogenic mutations in either the KIT or platelet-derived growth factor receptor alpha (PDGFRA) tyrosine kinase receptor genes and show differentiation along the lines of the interstitial cells of Cajal. Rarely, GISTs arise primarily in the omentum, mesentery, or retroperitoneum, at which sites they are referred to as "extragastrointestinal stromal tumors" (EGISTs). However, primary intrathoracic GIST arising in the pleura or lung has not been previously reported. We describe herein, a 62-year-old male who presented with a pleural-based mass unrelated to the esophagus that was morphologically typical of a spindle-cell GIST, showing strong immunoreactivity for KIT and DOG1, and harboring an exon 11 mutation in KIT. Ten years after resection, the tumor recurred as multiple masses in the pleura and mediastinum and was marginally reexcised. The patient was then treated with adjuvant imatinib mesylate with no evidence of further recurrences 13 months later. This seems to be the first EGIST arising above the diaphragm. This case shows a potential diagnostic pitfall with therapeutic consequences.

Recent advances in the management of gastrointestinal stromal tumors

This report focuses mainly on the major reduction of the risk of relapse of gastrointestinal stromal tumor (GIST) treated with imatinib, as identified in the American College of Surgeons Oncology Group (ACOSOG) Z9001 trial. It also focuses on the many unknowns associated with adjuvant imatinib therapy despite approvals by the US Food and Drug Administration and the European Medicines Agency, and on a new marker for the diagnosis of GIST.

Carbonic anhydrase II. A novel biomarker for gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are clinically distinct mesenchymal tumors, which generally result from expression of mutant KIT or PDGFRA receptor tyrosine kinase oncogenes. Most GISTs feature strong expression of KIT that serves as a crucial diagnostic adjunct. However, a subset of tumors lacks KIT expression and otherwise may also be difficult to distinguish from other sarcomas, including leiomyosarcoma. Because various carbonic anhydrase (CA) isozymes have been identified as potential treatment targets against different cancers, we evaluated CA II expression in 175 GISTs. Western blotting experiments indicated that CA II is highly expressed in GIST cell lines. Immunohistochemically, 95% of GISTs showed positive signal. The CA II expression in GISTs did not correlate with particular KIT or PDGFRA mutation types. CA II immunoreactivity was absent or low in other mesenchymal tumor categories analyzed. High CA II expression was associated with a better disease-specific survival rate than low or no expression (Mantel-Cox test, P<0.0001). The present results indicate that CA II is overexpressed in most GISTs, is quite selective to this tumor type among mesenchymal tumors, and therefore might be a useful biomarker in diagnostics.

The utility of discovered on gastrointestinal stromal tumor 1 (DOG1) antibody in surgical pathology-the GIST of it

DOG1 (discovered on GIST 1), known also as TMEM16A and ANO1, has emerged in recent years as a promising biomarker for gastrointestinal stromal tumors (GIST). It was originally discovered through microarray expression profiling analysis as gene that is highly expressed in GIST, and subsequent immunohistochemical studies have shown its use in its diagnosis. The results from several series have shown a high overall sensitivity and specificity for DOG1 in the detection of GISTs and about 6% of GISTs overall exhibiting a DOG1+/KIT-immunoprofile. DOG1 antibodies are more sensitive than KIT antibodies in detecting tumors of gastric origin, tumors with epithelioid morphology, and tumors harboring PDGFRA mutation. Furthermore, DOG1 immunoreactivity is rarely observed in other mesenchymal and nonmesenchymal tumor types. These results support the use of DOG1 as a diagnostic biomarker for GIST. When used in combination with KIT, this panel of diagnostic biomarkers can help pathologists and clinicians to identify more patients who may benefit from targeted therapies.

Targeted therapies of gastrointestinal stromal tumors (GIST)--the next frontiers

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal (GI) tract and are caused by activating KIT or PDGFRA mutations. GISTs can be successfully treated with the small molecule kinase inhibitor imatinib mesylate (Gleevec, Novartis) with response rates of up to 85%. However, complete responses are rare, and most patients will develop imatinib resistance over time. Recent results have shown that although imatinib effectively stimulates apoptotic cell death in sensitive GIST cells, a considerable proportion of cells does not undergo apoptosis, but instead enters a state of quiescence. Quiescence is characterized by a reversible withdrawal from the cell division cycle, during which the cells remain alive and metabolically active. It is conceivable that quiescence not only plays a pivotal role in the emergence of residual disease but also in creating a pool of tumor cells that survive continuous small molecule therapy and may hence represent the "seeds" for the outgrowth of resistant clones. This review will summarize the current knowledge about GIST biology and treatment response to imatinib including the induction of cellular quiescence in GIST. In addition, we will highlight future strategies to design more effective treatment options to overcome these problems with an aim towards cure of this hitherto untreatable tumor entity.

NCCN Task Force report: update on the management of patients with gastrointestinal stromal tumors

The standard of care for managing patients with gastrointestinal stromal tumors (GISTs) rapidly changed after the introduction of effective molecularly targeted therapies involving tyrosine kinase inhibitors (TKIs), such as imatinib mesylate and sunitinib malate. A better understanding of the molecular characteristics of GISTs have improved the diagnostic accuracy and led to the discovery of novel immunomarkers and new mechanisms of resistance to TKI therapy, which in turn have resulted in the development of novel treatment strategies. To address these issues, the NCCN organized a task force consisting of a multidisciplinary panel of experts in the fields of medical oncology, surgical oncology, molecular diagnostics, and pathology to discuss the recent advances, identify areas of future research, and recommend an optimal approach to care for patients with GIST at all stages of disease. The task force met for the first time in October 2003 and again in December 2006 and October 2009. This supplement describes the recent developments in the field of GIST as discussed at the October 2009 meeting.

Translating gene expression into clinical care: sarcomas as a paradigm

Whereas most solid tumors are characterized by considerable genetic instability and molecular heterogeneity, sarcomas include many subtypes with very specific underlying molecular events driving oncogenesis. Gene expression profiling and other modern techniques have consequently had particular success in identifying the critical biologic pathways active in specific sarcomas, yielding insights which can be translated into useful diagnostic biomarkers. Public availability of data sets and new sequencing-based technologies will accelerate this process. Molecular studies have also identified oncogenic pathways of particular importance in sarcomas which can be targeted by investigational drugs. Examples include histone deacetylases in translocation-associated sarcomas of young adults, Akt/mammalian target of rapamycin in pleomorphic sarcomas, and macrophage colony-stimulating factor in tenosynovial giant cell tumor. Despite challenges in organization and accrual, future clinical trials of sarcomas need to be designed that take into account specific molecular subtypes as distinct diseases.

c-kit (CD117) expression in human tumors and its prognostic value: an immunohistochemical analysis

c-kit functions as a tyrosine kinase receptor and represents a target for small molecule kinase inhibitors. The expression pattern for c-kit was studied in different human tumor types to their correlation with prognosis. Paraffin-embedded tumor tissues from 282 patients were analyzed immunohistochemically for c-kit expression. Survival and follow-up data were available from 192/282 (68%) patients. c-kit immunopositivity was found in 62/282 (22%) cases. c-kit expression was found in 14/83 (17%) colorectal cancers, in 13/62 (21%) breast cancers, in 7/20 sarcomas (35%), in 5/14 (36%) renal cell carcinomas, in 2/12 ovarian cancers (17%) and in 2/12 (17%) hepatocellular carcinomas. We found no significant correlation between c-kit expression and prognosis although a trend to a worse prognosis in patients with c-kit positive tumors could be observed. Expression of c-kit was found in tumor samples with varying intensities and infrequently.

Gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) have emerged from being poorly defined, treatment-resistant tumors to a well-recognized, well-understood, and treatable tumor entity within only one decade. The understanding of GIST biology has made this tumor a paradigm for molecularly targeted therapy in solid tumors and provides informative insights into the advantages and limitations of so-called targeted therapeutics. Approximately 85% of GISTs harbor activating mutations in KIT or the homologous receptor tyrosine kinase PDGFRA gene. These mutations are an early event in GIST development and the oncoproteins serve as a target for the small molecule tyrosine kinase inhibitors imatinib and sunitinib. The existing and emerging treatment options demand exact morphologic classification and risk assessment. Although, KIT (CD117) immunohistochemistry is a reliable diagnostic tool in the diagnosis of GIST, KIT-negative GISTs, GISTs showing unusual morphology as well as GISTs which progress during or after treatment with imatinib/sunitinib can be a challenge for pathologists and clinicians. This review focuses on GIST pathogenesis, morphologic evaluation, promising new immunohistochemical markers, risk assessment, the role of molecular analysis, and the increasing problem of secondary imatinib resistance and its mechanisms.

Peripheral nerve sheath tumors of the gastrointestinal tract: a multicenter study of 58 patients including NF1-associated gastric schwannoma and unusual morphologic variants

The frequency and morphological spectrum of gastrointestinal peripheral nerve sheath tumors (PNSTs) from consecutive case material has not been studied in the c-KIT era. We reviewed all mesenchymal gastrointestinal (GI) lesions at our departments according to current diagnostic criteria. PNSTs formed the third commonest group of mesenchymal GI tumors with a lower frequency (< or =5%) compared to gastrointestinal stromal tumors (GISTs; approximately 50%) and smooth muscle neoplasms ( approximately 30%). Granular cell tumors (GCTs; n = 31) and schwannomas (n = 22) were the most common types of PNSTs encountered. Rare tumors included neurofibromatosis 1 (NF1)-associated PNSTs (n = 5) and gastric perineurioma (n = 1). Thirteen schwannomas (including also some recent cases) were initially diagnosed as GIST, leiomyoma, or neurofibroma. Unusual histological variants included sigmoid GCT with prominent lipomatous component (n = 1), reticular-microcystic schwannoma of small (n = 1) and large (n = 1) bowel, NF1-associated gastric schwannoma (the first case to date), and psammomatous melanotic colonic schwannoma unrelated to Carney complex (n = 1). PNSTs coexisted with GIST in four patients (three had definite NF1). In conclusion, PNSTs of the GI tract are rare uniformly benign neoplasms that may show schwannian, perineurial, fibroblastic, or mixed differentiation. Most of them (92%) occurred sporadically unassociated with NF1 or NF2. Gastrointestinal PNSTs are still underrecognized by general pathologists. Awareness of their diverse morphology will help to avoid confusing them with smooth muscle neoplasms and GIST that they may closely mimic.

Advances in pathological diagnosis of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. The pathogenesis of GIST may be associated with the mutations of oncogenic c-kit or platelet-derived growth factor receptor alpha (PDGFRA). The pathological diagnosis of GIST needs a combined approach of macropathology, histopathology, immunohistochemistry and gene testing. Preoperative diagnosis is very important for patients with GIST, especially for those needing individualized treatment. In this article, we will review the recent advances in pathological diagnosis of GIST and the consensus criteria for risk stratification of GIST. Besides, we will also summarize the molecular biological parameters used for evaluation of the biological behavior of GIST.

Imatinib treatment for gastrointestinal stromal tumour (GIST)

Gastrointestinal stromal tumour (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. GISTs are believed to originate from intersticial cells of Cajal (the pacemaker cells of the gastrointestinal tract) or related stem cells, and are characterized by KIT or platelet-derived growth factor receptor alpha (PDGFRA) activating mutations. The use of imatinib has revolutionized the management of GIST and altered its natural history, substantially improving survival time and delaying disease progression in many patients. The success of imatinib in controlling advanced GIST led to interest in the neoadjuvant and adjuvant use of the drug. The neoadjuvant (preoperative) use of imatinib is recommended to facilitate resection and avoid mutilating surgery by decreasing tumour size, and adjuvant therapy is indicated for patients at high risk of recurrence. The molecular characterization (genotyping) of GISTs has become an essential part of the routine management of the disease as KIT and PDGFRA mutation status predicts the likelihood of achieving response to imatinib. However, the vast majority of patients who initially responded to imatinib will develop tumour progression (secondary resistance). Secondary resistance is often related to secondary KIT or PDGFRA mutations that interfere with drug binding. Multiple novel tyrosine kinase inhibitors may be potentially useful for the treatment of imatinib-resistant GISTs as they interfere with KIT and PDGFRA receptors or with the downstream-signalling proteins.