BACKGROUND: With the introduction of molecularly targeted therapy for 
gastrointestinal stromal tumors (GISTs), it became important to distinguish 
GISTs from leiomyosarcomas (LMSs). The authors sought to characterize the 
clinicopathologic features of these tumors in pediatric patients.
METHODS: The authors reviewed the medical records of 11 patients for whom GIST 
or LMS was diagnosed between March 1962 and July 2002 at St. Jude Children's 
Research Hospital and reclassified the tumors according to current histologic 
and immunophenotypic criteria. The authors also reviewed the literature 
pertaining to pediatric GISTs and LMSs.
RESULTS: Seven patients had GISTs, and four had LMS. The median age of the 
patients at diagnosis was 11.5 years. At diagnosis, metastases were present in 
one patient with GISTs and in another with LMS. Unlike the focal distribution of 
CD117 (KIT) in LMS, diffuse and strong immunostaining was observed in GISTs. 
Only GISTs expressed CD34. Six patients underwent complete resection (four with 
GISTs and two with LMS), four patients underwent incomplete resection (three 
with GISTs and one with LMS), and one patient (with LMS) underwent a biopsy 
only. Radiotherapy or chemotherapy was used to treat one patient with GISTs and 
three patients with LMS. One patient with a high-risk GIST (largest dimension of 
32 cm and high mitotic count) was treated with adjuvant imatinib mesylate 
outside the preferred setting of a clinical trial, due to concerns regarding the 
high risk of tumor recurrence. Four patients with GISTs and two with LMS 
survived median disease-free a median of 10.4 years and 4.3 years after 
diagnosis, respectively. Tumors in all but one survivor were completely 
resected.
CONCLUSIONS: KIT staining helped to distinguish GISTs from LMSs. Surgery was the 
treatment of choice for both entities, and tumor resectability was a key 
prognostic factor.