Objective  To describe the CT and MRI manifestations of extrapulmonary inflammatory myofibroblastic tumors (EPIMT).

  Methods  A retrospective analysis of images from 30 patients in Tianjin Medical University Cancer Institute and Hospital from January 2011 to August 2019 of EPIMT confirmed by surgery or puncture pathology and immunohistochemistry was conducted. The features examined included lesion location, size, shape, boundary, density/signal, and enhancement pattern.

  Results  Of the 30 cases, 28 were determined to have a single isolated tumor, while 2 cases had two isolated tumors. Among the 32 tumors, 20 had an irregular shape and 11 were round or oval, while a single tumor had the appearance of a multinodular fusion. Most of the lesions had ill-defined borders and showed signs of invading or adhering to the surrounding tissue. Cystic degeneration and necrosis were seen in 8 tumors, with calcification and hemorrhage also occasionally observed. On contrast-enhanced CT scans, significant or moderate enhancement was observed in most cases, mainly with a progressive and continuous enhancement pattern. A few cases showed heterogeneous enhancement with a slow wash in and slow wash out pattern. On contrast-enhanced MRI, 9 cases demonstrated moderate or significantly delayed enhancement. Immunohistochemical staining showed a Ki-67 proliferation index of less than 5% in 50% of the tumors. Positive staining for Vimentin, SMA and ALK were measured in 93.3%, 86.7%, and 31.8% of tumors, respectively, while the 81.8% of tumors were negative for S-100.

  Conclusions  In EPIMT, some specific pathological manifestations can be detected using CT and MRI. Typical features include the presence of a single isolated tumor, ill-defined borders, inflammatory infiltration, progressive and continuous enhancement or slow wash in and slow wash out, and the presence of lymph nodes around the tumor. Comparative analysis between pathology and imaging will be helpful in future to improve the diagnostic accuracy for types of EPIMT.