Complete extragastric growth in a giant gastrointestinal stromal tumor: report of a case.

Gastrointestinal stromal tumors (GISTs) are characterized by remarkable variability in their differentiation potential, but most of these lesions do not display convincing smooth muscle or neuronal differentiation. Here we report the case of a 65-year-old woman who underwent a perfect resection of a large submucosal tumor that displayed extragastric growth. The specimen was revealed to be an elastic soft tumor, 18 x 25 x 11 cm in size. Histologically, the tumor consisted of spindle-shaped cells, with a mitotic rate of 12 per 10 high-power fields. Immunohistochemically, the tumor showed positive staining for CD34 and c-kit but negative staining for alpha-smooth muscle actin, Desmin, and s-100 protein. From these findings, the tumor was diagnosed as an uncommitted type of GIST with high-grade malignancy. This case needs careful and long-term follow-up to monitor for signs of local recurrence or distant metastasis.