Inflammatory myofibroblastic tumor arising from soft tissues of extremities harboring a novel CLIP2‐ALK fusion

Abstract

A 34-year-old Chinese woman found a lump in her left leg for more than 3 weeks without any discomfort. Grossly, the tumor was relatively well delineated with focal infiltration. Histopathologic evaluation showed a compact fascicular spindle cell proliferation with variable myxoid and collagenous stroma and scattered inflammatory infiltrate. Immunohistochemically, the tumor cells showed positive expression of ALKD5F3 and SMA and negative expression of CD34, desmin, and cytokeretin. Fluorescence in situ hybridization analysis of the ALK locus showed break-apart signals in 20% of tumor cells, and DNA sequencing discovered a novel CLIP2-ALK fusion gene. The lesion was diagnosed as an inflammatory myofibroblastic tumor (IMT). To the best of our knowledge, this is the first case with CLIP2-ALK gene fusion in the somatic soft tissue IMTs.

A Novel CASC15-ALK and TFG-ROS1 Fusion Observed in Uterine Inflammatory Myofibroblastic Tumor

“…The ALK fusion partners identified in IMT of the female genital tract include IGFBP5, THBS1, FN1, DES, TIMP3, SYN3, SEC31A, TNS1, and TPM3 (3,5,7-10). In addition to the above genes, in IMTs other than those in the female reproductive tract, more than 20 different genes are ALK fusion partners, including TPM4, RANBP2, TFG, MSN, CARS, ALO17 (KIAA1618), ATIC, LMNA, PRKAR1A, CLTC, FN1, PPFIBP1, NPM1, RANBP2, EML4, NUMA1, CLIP1, TRAF3, HNRNPA1, SQSTM1, VCL, and KIF5B (2,(22)(23)(24)(25)(26)(27)(28)(29)(30)(31). In this study, there was one IMT case harboring a novel CASC15-ALK fusion.…”