Gastrointestinal stromal tumor of the uterus: a case report with genetic analyses of c-kit and PDGFRA genes.

The author reports a very rare case of a gastrointestinal stromal tumor in the uterus. A 74-year-old woman was admitted to our hospital because of pelvic pain. Imaging modalities showed a large tumor of the posterior aspect of the uterus, and enucleation was performed. The tumor was attached to the posterior uterus, similar to subserosal leiomyoma. No attachment to the gastrointestinal organs was recognized. The tumor was soft, tan, and measured 13 x 15 x 12 cm. The tumor consisted of cellular spindle cells with focal necrotic areas. Mitotic figures were noted in 3 of 50 high-power fields. The tumor cells were positive for KIT, CD34, platelet-derived growth factor receptor alpha, and vimentin, but negative for alpha-smooth muscle actin, S100 protein, p53 protein, HMB45, and desmin. Ki-67 labeling was 3%. Five normal uteruses used as controls showed KIT-positive Cajal-like mesenchymal cell scattering in the myometrium. Genetic analyses of the c-kit gene (exons 9, 11, 13, and 17) and platelet-derived growth factor receptor alpha gene (exons 12 and 18) revealed a point mutation at codon 559 (GTT-->GAT) of exon 11 of the c-kit gene. Other exons showed no abnormalities. This case shows that gastrointestinal stromal tumor may occur in the uterus.