Desmoid is a tumour with a local aggressiveness; GIST with KIT mutation responds massively to target treatment as IMATINIB, whereas soft tissue sarcoma and leiomyosarcoma are very aggressive with poor response to systemic therapies.
In contrast, leiomyosarcoma of the gastrointestinal tract has become a very rare entity in the 'KIT' era, and its molecular pathogenetic mechanism is unclear.
Immunohistochemical staining for DOG-1, C-Kit (CD117) and protein kinase C theta (PKCθ) was performed on FNA cell-block preparations representing 30 GISTs, 17 leiomyosarcomas, 16 melanomas, 16 schwannomas, 11 adenoid cystic carcinomas, and 8 leiomyomas.
Immunoreactivity for several smooth muscle markers including desmin on tumor cells, low amplification of both c-kit and PDGFRA cDNA on polymerase chain reaction, and absence of c-kit gene mutation in exons 9 and 11 strongly suggested that the tumor was not a gastrointestinal stromal tumor but a true leiomyosarcoma.
Molecular genetic analysis of exon 11, analyzed by direct DNA sequencing, was performed for all of the c-KIT-positive uterine leiomyosarcomas.No mutations were found.
Lately reports of efficacy of a specific anticancer drug with imatinib (ST1571) based on specific molecular abnormalities of proto-oncogene c-kit present in gastrointestinal stromal tumors induced us to identify the c-kit phenotype also in uterine leiomyosarcomas.