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.