Gastrointestinal Stromal Tumors: Imaging Features Before and After Treatment.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract, with most occurring in the stomach. GISTs may present with clinical symptoms (eg, gastrointestinal bleeding) or may be found incidentally at surgery, endoscopy, or imaging. At initial staging, GISTs often appear as well-circumscribed, round, solid masses. Small tumors may appear solid, whereas larger tumors may demonstrate central areas of necrosis. At follow-up imaging, decreasing tumor attenuation at computed tomographic indicates treatment response even in the setting of stable tumor size. Localized tumors are treated with resection. Imatinib mesylate, a tyrosine kinase inhibitor, is typically prescribed for metastatic disease and increasingly in a neoadjuvant role before resection. Imaging plays a key role in the identification of GISTs, evaluation of tumor extent and presence or absence of metastatic disease, and in assessing response to therapy.

ACR Appropriateness Criteria Renal Cell Carcinoma Staging.

Renal cell carcinoma accounts for 2%-3% of all visceral malignancies. Preoperative imaging can provide important staging and anatomic information to guide treatment decisions. Size of the primary tumor and degree of local invasion, such as involvement of perinephric fat or renal sinus fat, and tumor thrombus in renal veins and inferior vena cava are important detriments to local staging of primary tumor. Both kidneys are assessed for presence of other synchronous lesions. The ACR Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and application by the panel of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Imaging Complications of Renal Transplantation.

Renal transplant complications are categorized as those related to the transplant vasculature, collecting system, perinephric space, renal parenchyma, and miscellaneous complications including posttransplant lymphoproliferative disorder. Many of these renal transplant complications are diagnosed with imaging. Medical complications including rejection, acute tubular necrosis, and drug toxicity also can impair renal function. These medical complications are typically indistinguishable at imaging, and biopsy may be performed to establish a diagnosis. Normal transplant anatomy, imaging techniques, and the appearances of renal transplant complications at ultrasound, computed tomography, and MR imaging are reviewed.

Angiomatoid fibrous histiocytoma: novel MR imaging findings.

OBJECTIVE: To describe novel MR imaging features, and clinical characteristics of soft tissue angiomatoid fibrous histiocytoma (AFH) at presentation, local recurrence, and metastases. MATERIALS AND METHODS: We described the MRI findings of six cases of histologically proven AFH. Pathologic findings, clinical presentation, and outcome were reviewed. RESULTS: Lesions were primarily cystic. At initial presentation, tumors were surrounded by low signal intensity fibrous pseudocapsule. High signal intensity consistent with the lymphoplasmacytic infiltrate was seen in T2-weighted and post-contrast images as a rim over the hypointense pseudocapsule (double rim sign). High signal intensity infiltrating tumoral cords extended into adjacent tissues, through pseudocapsular defects on T2-weighted and post-contrast images. The cystic component and tumor cell nodularity were demonstrated at post-contrast images. Clinically, lesions were often thought to be benign, underwent marginal resection, developed local recurrence, and one developed second recurrence consisting of metastases. Recurrent tumors appeared as multiple masses, misinterpreted as post-surgical changes. An intramuscular recurrence demonstrated double rim and infiltrating margin. CONCLUSIONS: A predominantly well-circumscribed, primarily cystic mass with double-rim and marginal infiltration on MRI suggests the possibility of AFH, in particular in child or young adult. Inclusion of these novel observations in AFH differential diagnosis may have a significant impact on treatment and prevention of recurrence.

Case report: MR imaging features of disseminated uterine leiomyosarcoma presenting after hysterectomy with morcellation.

A 53-year-old woman underwent elective hysterectomy for symptomatic anemia secondary to abnormal uterine bleeding. She presented 15 months later with complaints of abdominal fullness. Abdominopelvic magnetic resonance imaging demonstrated multiple confluent enhancing solid masses centered in the pelvis and extending cranially to the level of the umbilicus. Additional separate nodules also were visible along the peritoneum. Biopsy demonstrated leiomyosarcoma. Additional clinical information was obtained, which revealed that the patient's prior hysterectomy was performed with morcellation. In November 2014, the United States Food and Drug Administration issued a warning discouraging the use of morcellation during hysterectomy and myomectomy because of the risk of seeding unsuspected malignancy. Radiologists should be aware of this potential complication of morcellation and its imaging appearance so that the correct diagnosis can be suggested in the imaging report.

Primary biliary tract malignancies: MRI spectrum and mimics with histopathological correlation.

Contrast-enhanced magnetic resonance imaging and magnetic resonance cholangiopancreatography (MRCP), due to their excellent soft tissue contrasts, have become first-line noninvasive tests in the characterization and detection of both hepatic and pancreaticobiliary pathologies. MRCP is also helpful in detecting the level and cause of obstruction in patients presenting with jaundice. Cholangiocarcinoma (CCA) is the most common primary malignant tumor arising from the bile duct epithelium, with extrahepatic tumors presenting more often than with intrahepatic ones. However, the diagnosis and management of CCA is made more complex by a variety of malignant and benign conditions that resemble CCA, including hepatocellular carcinoma variants such as the fibrolamellar variant of hepatocellular carcinoma, cholangiocellular carcinoma, biliary metastases, hepatic inflammatory pseudotumor, lymphoepithelioma-like carcinoma, confluent fibrosis, primary sclerosis cholangitis, and the secondary sclerosing cholangitis complex. Consequently, knowledge of the underlying risk factors and imaging characteristics of these conditions is important in differentiating between neoplastic and non-neoplastic conditions in order to reach a definite diagnosis. Endoscopic retrograde cholangiopancreatography should be reserved for those patients who require intervention or biopsy for histopathological diagnosis.

Posttransplantation lymphoproliferative disease: proposed imaging classification.

Posttransplantation lymphoproliferative disease (PTLD) is the second most common tumor in adult transplant recipients. Most cases of PTLD are attributed to Epstein-Barr virus. Decreased levels of immunosurveillance against this tumor virus as a result of immunosuppressive regimens are thought to account for most cases of PTLD. Histologically, PTLD ranges from relatively benign lymphoid hyperplasia to poorly differentiated lymphoma, and tissue sampling is required to establish the subtype. The frequency of PTLD varies depending on the type of allograft and immunosuppressive regimen. PTLD has a bimodal manifestation, with most cases occurring within the first year after transplantation and a second peak occurring 4-5 years after transplantation. Patients are often asymptomatic or present with nonspecific symptoms, and a mass visible at imaging may be the first clue to the diagnosis. Imaging plays an important role in identifying the presence of disease, guiding tissue sampling, and evaluating response to treatment. The appearance of PTLD at imaging can vary. It may be nodal or extranodal. Extranodal disease may involve the gastrointestinal tract, solid organs, or central nervous system. Solid organ lesions may be solitary or multiple, infiltrate beyond the organ margins, and obstruct organ outflow. Suggestive imaging findings should prompt tissue sampling, because knowledge of the PTLD subtype is imperative for appropriate treatment. Treatment options include reducing immunosuppression, chemotherapy, radiation therapy, and surgical resection of isolated lesions.

Mesenteric masses: approach to differential diagnosis at MRI with histopathologic correlation.

Magnetic resonance imaging (MRI) is an outstanding tool for the identification and characterization of mesenteric masses. Mesenteric masses may be solid or cystic. Most solid mesenteric masses are neoplastic, with sclerosing mesenteritis a notable exception. Entirely cystic mesenteric masses are typically benign. The excellent soft-tissue contrast afforded by MRI aids in narrowing the differential diagnosis of mesenteric masses. Accurately characterizing both solid and cystic mesenteric masses is important, as management ranges from active surveillance to medical management to surgical resection, depending on the tissue composition of the mass. An MRI-based approach to the differential diagnosis of mesenteric masses is presented.