Fig. 2: Low-grade spindle-cell neoplasms with NTRK1 rearrangements.

a Monomorphic spindle-cell population with intracytoplasmic vacuoles (b), mimicking lipoblasts or GIST cells (case 5). c Storiform pattern of growth, focally reminiscent of dermatofibrosarcoma protuberans (case 6); in other areas of the same tumor, long fascicles of spindle cells resembling desmoid or low-grade MPNST (d).