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

DOG1: a novel marker of salivary acinar and intercalated duct differentiation

Anoctamin-1 (ANO1) (DOG1, TMEM16a) is a calcium-activated chloride channel initially described in gastrointestinal stromal tumors, but now known to be expressed in a variety of normal and tumor tissues including salivary tissue in murine models. We herein perform a comprehensive survey of DOG1 expression in 156 cases containing non-neoplastic human salivary tissues and tumors. ANO1 mRNA levels were significantly higher (8-fold increase, P<0.0001) in normal parotid tissue (n=6) as compared with squamous mucosa (n=15). By immunohistochemistry, DOG1 showed a diffuse moderate (2+) apical membranous staining pattern in normal serous acini, 1+ apical membranous pattern in mucous acini, and variable 1-2+ apical staining of distal intercalated ducts. Myoepithelial cells, striated and excretory ducts were invariably negative. All acinic cell carcinomas (n=28) were DOG1 positive demonstrating a complex mixture of intense (3+) apical membranous, cytoplasmic and complete membranous staining. Most ductal tumor types were negative or only showed a subset of positive cases. Within the biphasic tumor category, adenoid cystic carcinomas (18/24 cases) and epithelial-myoepithelial carcinomas (8/15 cases) were frequently positive, often showing a distinctive combined apical ductal and membranous/cytoplasmic myoepithelial staining profile. Thus, DOG1 staining is a marker of salivary acinar and to a lesser extent intercalated duct differentiation. Strong staining can be used to support the diagnosis of acinic cell carcinoma. DOG1 may also be a marker of a 'transformed' myoepithelial phenotype in a subset of biphasic salivary gland malignancies.

Esophageal gastrointestinal stromal tumor: report of 7 patients

Abstract Purpose: To evaluate imaging features of esophageal gastrointestinal stromal tumors (GIST) with clinical and histopathologic correlation and imaging follow-up. Materials and methods: In this institutional review board-approved, Health Insurance Portability and Accountability Act-compliant retrospective study, 14 patients with pathologically proven esophageal GIST seen from January 2001 to October 2011, 7 patients (4 women; mean age 70 years, range 56–87 years) who had imaging of primary tumor and follow-up imaging at our institution were included. Imaging studies were evaluated by 3 radiologists in consensus. Location, size and imaging features of primary tumor and metastases, if any, were recorded, and correlated with pathologic (histopathologic subtype, presence of necrosis, mitotic rate, immunohistochemical profile) and clinical (treatment-related changes, distant spread and outcome) parameters. Results: Of 7 tumors, 5 were located in the lower esophagus and 2 in mid-esophagus. Four were intraluminal, 2 were exophytic, and 1 was intramural. All 7 patients underwent computed tomography (CT); tumors appeared as well-circumscribed, hypoattenuating masses showing mild enhancement, with mean size of 5.7 × 4.2 cm. Necrosis and calcification were seen in 1 tumor each. Five patients underwent fluorodeoxyglucose (FDG)-positron emission tomography (PET)/CT. GISTs were FDG avid with mean standardized uptake value (SUV)_max of 9.5 (4.5–12.3). All tumors were positive for KIT (7/7) and CD34 (6/6). Distant metastases to liver and pleura were seen in 1 patient. On imatinib treatment, the tumors responded with decreased attenuation values and unchanged size on CT, and decreased SUV_max of primary tumor and metastases on FDG-PET/CT. Conclusion: Esophageal GISTs are well-circumscribed, FDG-avid, hypoattenuating masses that can metastasize to liver and pleura, and respond to imatinib treatment with decreased attenuation value on CT and decreased SUV_max on FDG-PET/CT.

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.

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.

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.