Current update on molecular cytogenetics, diagnosis and management of gastrointestinal stromal tumors

Gastrointestinal stromal tumors(GISTs)are the most common mesenchymal tumors of the gastrointestinal(GI)tract and are thought to arise from precursors of the interstitial cells of Cajal.GISTs can arise anywhere in the GI tract,but most commonly originate from the stomach and small intestine.The majority of GISTs occur as a result of activating mutations in two receptor protein tyrosine kinases:KIT and/or platelet-derived growth factor receptor-α.Mutational analyses allow for predicting patient prognosis and treatment response.Clinical presentations can vary from no symptoms,typical in the case of small incidentally found tumors,to GI bleeding,abdominal discomfort,and ulcer-related symptoms when the tumor is enlarged.Imaging plays a critical role in the diagnosis and management of these tumors with multiphasic computed tomography serving as the imaging modality of choice.Magnetic resonance imaging and positron emission tomography-computed tomography can serve as imaging adjuncts in lesion characterization,especially with liver metastases,and subsequent staging and assessment for treatment response or recurrence.Surgical resection is the preferred management for small GISTs,while tyrosine kinase inhibitors−imatinib mesylate and sunitinib malate−serve as crucial molecular-targeted therapies for locally advanced and metastatic GISTs.This review article highlights the clinical presentation,pathology and molecular cytogenetics,imaging features,and current management of GISTs.

Extrahepatic biliary cancer:New staging classification

Tumor staging defines the point in the natural history of the malignancy when the diagnosis is made. The most common staging system for cancer is the tumor, node, metastases classification. Staging of cancers provides useful parameters in the determination of the extent of disease and prognosis. Cholangiocarcinoma are rare and refers to cancers that arise from the biliary epithelium. These tumors can occur anywhere along the biliary tree. These tumors have been previously divided into extrahepatic and intrahepatic lesions. Until recently the extrahepatic bile duct tumors have been considered as a single entity per American Joint Com- mission on Cancer (AJCC) staging classification. The most recent changes to the AJCC classification of bile duct cancers divide the tumors into two major catego- ries: proximal and distal tumors. This practical classifi- cation is based on anatomy and surgical management. High quality cross-sectional computed tomography (CT) and/or magnetic resonance (MR) imaging of the abdomen are essential information to accurately stage this tumors. Imaging plays an important role in diag-nosis, localization, staging and optimal management of cholangiocarcinoma. For example, it helps to localize the tumor to either perihilar or distal bile duct, both of which have different management. Further, it helps to accurately stage the disease and identify the presence of significant nodal and distant metastasis, which may preclude surgery. Also, it helps to identify the extent of local invasion, which has a major impact on the management. For example, extensive involvement of hepatic duct reaching up to second-order biliary radi- cals or major vascular encasement of portal vein or hepatic arteries precludes curative surgery and patient may be managed by palliative therapy. Further, imag- ing helps to identify any anatomical variations in the hepatic arterial or venous circulation and biliary ductal system, which is vital information for surgical planning. This review presents relevant clinical presentation and imaging acquisition and presentation for the accurate staging classification of bile duct tumors based on the new AJCC criteria. This will be performed with the as- sistance of anatomical diagrams and representative CT and MR images. The image interpretation must include all relevant imaging information for optimum staging. Detailed recommendations on the items required on the radiology report will be presented.

Features of primary pancreatic lymphoma:A bi-institutional review with an emphasis on typical and atypical imaging features

BACKGROUND Primary pancreatic lymphoma(PPL)is a rare neoplasm.Being able to distinguish it from other pancreatic malignancies such as pancreatic ductal adenocarcinoma(PDAC)is important for appropriate management.Unlike PDAC,PPL is highly sensitive to chemotherapy and usually does not require surgery.Therefore,being able to identify PPL preoperatively will not only direct physicians towards the correct avenue of treatment,it will also avoid unnecessary surgical intervention.AIM To evaluate the typical and atypical multi-phasic computed tomography(CT)imaging features of PPL.METHODS A retrospective review was conducted of the clinical,radiological,and pathological records of all subjects with pathologically proven PPL who presented to our institutions between January 2000 and December 2020.Institutional review board approval was obtained for this investigation.The collected data were analyzed for subject demographics,clinical presentation,laboratory values,CT imaging features,and the treatment received.Presence of all CT imaging findings including size,site,morphology and imaging characteristics of PPL such as the presence or absence of nodal,vascular and ductal involvement in these subjects were recorded.Only those subjects who had a pre-treatment multiphasic CT of the abdomen were included in the study.RESULTS Twenty-nine cases of PPL were diagnosed between January 2000 and December 2020(mean age 66 years;13 males/16 females).All twenty-nine subjects were symptomatic but only 4 of the 29 subjects(14%)had B symptoms.Obstructive jaundice occurred in 24%of subjects.Elevated lactate dehydrogenase was seen in 81%of cases,whereas elevated cancer antigen 19-9 levels were present in only 10%of cases for which levels were recorded.The vast majority(90%)of tumors involved the pancreatic head and uncinate process.Mean tumor size was 7.8 cm(range,4.0-13.8 cm).PPL presented homogenous hypoenhancement on CT in 72%of cases.Small volume peripancreatic lymphadenopathy was seen in 28%of subjects.Tumors demonstrated encasement of superior mesenteric vessels in 69%of cases but vascular stenosis or occlusion only manifested in 5 out of the twentynine individuals(17%).Mild pancreatic duct dilatation was also infrequent and seen in only 17%of cases,whereas common bile duct(CBD)dilation was seen in 41%of subjects.Necrosis occurred in 10%of cases.Size did not impact the prevalence of pancreatic and CBD dilation,necrosis,or mesenteric root infiltration(P=0.525,P=0.294,P=0.543,and P=0.097,respectively).Pancreatic atrophy was not present in any of the subjects.CONCLUSION PPL is an uncommon diagnosis best made preoperatively to avoid unnecessary surgery and ensure adequate treatment.In addition to the typical CT findings of PPL,such as homogeneous hypoenhancement,absence of vascular stenosis and occlusion despite encasement,and peripancreatic lymphadenopathy,this study highlighted many less typical findings,including small volume necrosis and pancreatic and bile duct dilation.

Current update on imaging for pancreatic neuroendocrine neoplasms

Pancreatic neuroendocrine neoplasms(panNEN)are a heterogeneous group of tumors with differing pathological,genetic,and clinical features.Based on clinical findings,they may be categorized into functioning and nonfunctioning tumors.Adoption of the 2017 World Health Organization classification system,particularly its differentiation between grade 3,well-differentiated pancreatic neuroendocrine tumors(panNET)and grade 3,poorly-differentiated pancreatic neuroendocrine carcinomas(panNEC)has emphasized the role imaging plays in characterizing these lesions.Endoscopic ultrasound can help obtain biopsy specimen and assess tumor margins and local spread.Enhancement patterns on computed tomography(CT)and magnetic resonance imaging(MRI)may be used to classify panNEN.Contrast enhanced MRI and diffusion-weighted imaging have been reported to be useful for characterization of panNEN and quantifying metastatic burden.Current and emerging radiotracers have broadened the utility of functional imaging in evaluating panNEN.Fluorine-18 fluorodeoxyglucose positron emission tomography(PET)/CT and somatostatin receptor imaging such as Gallium-681,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid–octreotate PET/CT may be useful for improved identification of panNEN in comparison to anatomic modalities.These new techniques can also play a direct role in optimizing the selection of treatment for individuals and predicting tumor response based on somatostatin receptor expression.In addition,emerging methods of radiomics such as texture analysis may be a potential tool for staging and outcome prediction in panNEN,however further investigation is required before clinical implementation.