Introduction:
Leiomyosarcoma is a type of Non-Rhabdomyosarcoma Soft Tissue Sarcoma (NRSTS) derived from smooth muscle stem cells. Among pediatric patients, NRSTS are exceedingly rare cancers, comprising approximately 1-7% of all pediatric cancer cases [1-4]. Among NRSTS, the incidence of pediatric leiomyosarcomas is estimated to be approximately <1%, with most cases among adolescent patients [1,4]. They can present in the trunk, head and neck region, and upper or lower limbs [1]. Pediatric leiomyosarcoma treatment is extrapolated from the treatment of NRSTS and includes a combination of surgery, radiation and chemotherapy depending on the tumor grade, tumor size, extent of resection and presence of metastases [5]. Spunt et al recently described 3 risk-based groups approach of NRSTS including low risk, intermediate risk and high-risk disease. Low risk group had event free survival (EFS) of 89% and overall survival (OS) of 96%; intermediate risk group had EFS of 65% and OS of 79% and high-risk group had EFS of 21% and OS of 35%. They noted that most of the low risk group patients did well with surgery alone while the survival was poor for the intermediate and high-risk groups despite chemotherapy and radiation therapy. The lack of response to the conventional chemotherapy and radiation has generated interest in molecular targeted therapy for NRSTS. Pazopanib, a tyrosine kinase inhibitor has shown some activity in NRSTS including leiomyosarcoma [12]. A recent COG study, ARST1321, is evaluating the effect of adding tyrosine kinase inhibitor to chemotherapy and radiation back bone for NRSTS.
The genomic landscape of pediatric leiomyosarcoma is poorly understood. Here we describe molecular findings in a child with leiomyosarcoma including a novel gene rearrangement.