CT and MRI findings in KIT-weak or KIT-negative atypical gastrointestinal stromal tumors

Abstract

The large majority of gastrointestinal stromal tumors (GIST) can be diagnosed on the basis of KIT immunoreactivity. However, some atypical tumors show weak or negative KIT expression. We studied the imaging characteristics of atypical GIST, reviewing CT and MRI findings in ten patients (eight men, two women; mean age 59 years) with atypical GIST. Radiological studies were evaluated by two radiologists by consensus and included CT and MR imaging in all patients. Pathological diagnoses were made from surgery and confirmed by the polymerase-chain reaction (PCR) to amplify both exons of the c-kit gene and PDGFRA gene. The CT and MR examinations revealed a heterogeneous mass of the stomach containing cystic regions and soft tissue elements in all cases. All lesions were extraluminal masses and had an exophytic epicenter. On T1-weighted MR images soft tissue elements of the tumors were of homogeneously low- (n=3) or iso-signal intensity (n=7) compared with the liver parenchyma. On fast spin-echo T2-weighted MR images soft tissue elements of all tumors showed cystic regions of significantly high signal intensity interspersed with septumlike structures of low signal intensity. All lesions exhibited homogeneously (n=4) or heterogeneously (n=6) mild to moderate enhancement of soft tissue elements. Despite the relatively small number of patients CT and MRI findings of atypical GIST are a submucosal mass with soft tissue elements and cystic regions.

Use of conventional MR imaging and diffusion‐weighted imaging for evaluating the risk grade of gastrointestinal stromal tumors

“…Previous studies (14, 18, 19) showed that typical GISTs appear as inhomogeneous enhancing extraluminal masses with either well‐defined or irregular borders on conventional MR sequences, such as T1W/T2W imaging and Gd‐DTPA‐enhanced images. A larger tumor size (≥ 5 cm) was found to have a predictive value with respect to high‐risk GISTs (11).…”

Prognostic factors affecting survival after surgical resection of gastrointestinal stromal tumours: a two-unit experience over 10 years

“…The primary tumour sites noted in our study are similar to other previous reports [ 18 , 19 ], with a similar demographic of presenting symptoms including gastrointestinal bleeding, abdominal pain and the presence of an abdominal mass [ 20 - 22 ]. CT and MRI are generally used for the preoperative imaging of GISTs [ 23 - 25 ]. However, there are no well-established, published guidelines to help surgeons determine the optimal manner in which to evaluate this intraabdominal, site-specific class of tumours.…”

Extragastrointestinal stromal tumor of lesser omentum: a challenging radiological and histological diagnosis

“…Neither CT nor MRI are currently able to differentiate between conventional GISTs and atypical (c-kit negative) GISTs [16]. Pathologists can be helped towards definitive diagnosis by other cellular markers (for example DOG-1 is positive in 40% of all kitnegative GISTs) or by molecular analysis of the KIT and PDGFRA genes.…”