In this study, we present a rare and difficult case of epithelioid inflammatory myofibroblastic sarcoma (EIMS) in abdominal cavity. A 47-year-old female presented as left upper abdominal pain for 6 months and abdominal distention for 1 month. CT examination showed a solid mass in the left upper intra-abdomen. Grossly, the tumor was found in the mesenterium of colon with the size of 7.5 × 6.5 × 3.5 cm, and was solid and gray-yellowish in the cut surface. Focal myxomatous appearance was observed. Microscopically, stromal myxoid change together with prominant infiltrated lymphocytes, neutrophils and eosinophils were found in the tumor, and the tumor cells were round, epithelioid with vesicular nuclei, large prominant nucleoli and high mitotic rate. Immunohistochemically, strong diffused positive for vimentin, desmin, ALK (nuclear membrane staining pattern) and AAT, focally positive for CD99 and CD30, were showed, Ki67 index was about 20%; Especially, WT-1 and D240 were focally expressed in this tumor. FISH analysis showed rearrangement of ALK, and reverse-transcription polymerase chain reaction (RT-PCR) analysis was used to detect the fusion location of the RANBP2 and ALK gene. The diagnosis of EMIS was made based on its location, typical morphology, the immunohistochemical features especially the nuclear membranous immunostaining of ALK and rearrangement of RANBP2-ALK. The tumor showed higher aggressive behaviors and a poor prognosis. The differential diagnosis and other treatments of EMIS are also discussed in the present study. This finding may increase the case information of EMIS.
Keywords: ALK; Epithelioid inflammatory myofibroblastic sarcoma; retroperitoneal.