Spindle cell tumor with EWS-WT1 transcript and a favorable clinical course: a variant of DSCT, a variant of leiomyosarcoma, or a new entity? Report of 2 pediatric cases.

We report 2 intra-abdominal tumors originally diagnosed as leiomyosarcomas, occurring in adolescents, one as a second malignancy after a Hodgkin lymphoma. Both tumors exhibited unusual morphologic features characterized by spindle cells arranged in sheets or in fascicles, devoid of the typical desmoplastic stroma. Cytokeratins and mesenchymal markers, including smooth muscle actin, desmin, and muscle specific actin, were coexpressed in the tumor cells, whereas EMA was negative. Reverse transcription-polymerase chain reaction analysis showed an EWS-WT1 fusion transcript. Both patients are alive and in complete remission at 3 and 13 years after diagnosis, respectively. These tumors raise a variety of diagnostic possibilities. They could represent intra-abdominal desmoplastic small round cell tumor, with histologic features of epithelioid leiomyosarcoma or an unusual subtype of leiomyosarcoma with an EWS-WT1 transcript. Alternatively, they could represent an unrecognized subgroup of tumors with spindle cell morphology, bearing the same translocation as desmoplastic small round cell tumor, but characterized by a more favorable clinical course.