CT, MRI, and FDG-PET/CT imaging findings of abdominopelvic desmoplastic small round cell tumors: Correlation with histopathologic findings

Abstract

Objective To analyze computed tomography (CT), magnetic resonance imaging (MRI), and fluorodeoxyglucose-positron emission tomography (FDG-PET)/CT imaging features of abdominopelvic desmoplastic small round cell tumor (DSRCT) and to improve the diagnostic efficacy of these techniques for the detection of such tumor. Methods We retrospectively analyzed 7 cases of abdominopelvic DSRCT confirmed by histopathologic analysis. Among the 7 patients, 5 patients had undergone CT scanning, 2 of which were also examined with FDG-PET/CT imaging, and 2 had undergone MRI. Unenhanced and contrast-enhanced examinations were performed in all patients, and 2 patients had also undergone dynamic CT contrast-enhanced examinations. Image characteristics, such as shape, size, number, edge, attenuation, and intensity of each lesion before and after contrast enhancement were analyzed and compared with the pathomorphology of the tumors. Results Multiple large masses in the abdominopelvis were detected in 6 cases, and a large mass in the pelvis was detected in 1 case. Six cases showed largest mass in pelvis, and 1 case in mesentery. None of the masses had a definite organ origin. CT showed soft tissue masses with patchy foci of hypodense areas. MR T1-weighted images revealed lesions with mild hypointense areas and patchy hypointense areas in 2 cases and lesions with patchy hyperintense areas in 1 case. T2-weighted images showed lesions with mixed isointense and hyperintense areas in 1 case and lesions with mixed hypointense, isointense, and hyperintense areas in another. Contrast-enhanced CT and T1-weighted images showed mildly heterogeneous enhancement of the lesions. Other associated findings included peritoneal seeding ( n = 3), peritoneal effusions ( n = 3), hepatic metastasis ( n = 2), bone metastasis ( n = 1), and mesenteric and retroperitoneal lymphadenopathy ( n = 4). FDG-PET/CT showed multiple nodular foci of increased metabolic activity in the abdominopelvic masses, in the hepatic and right ilium in 1 case and foci of increased metabolic activity in the pelvic mass in another. Conclusion Radiological findings of DSRCT include multiple masses with heterogeneous density/intensity and without an organ origin. Other common associated findings include peritoneal seeding, peritoneal effusion, hepatic metastasis, and retroperitoneal lymphadenopathy. DSRCT should be considered in the differential diagnosis of regional tumors in adolescents and young adults. FDG-PET/CT can provide additional information on the stage of the tumor.