Gastric stromal tumor with peritoneal nodules in pregnancy: tumor spread or rare variant of diffuse leiomyomatosis.

Gastric tumors discovered during pregnancy are rare. A cystic gastric stromal tumor with adjacent peritoneal nodules and associated with ascites was encountered in a 32-year-old pregnant patient. On initial clinical evaluation the mass was thought to originate from the uterine adnexa. The tumor itself was composed of uniform spindle cells with minimal mitotic activity. Immunohistochemical and ultrastructural studies were consistent with a gastrointestinal stromal tumor (GIST). Small nodules on the gastric serosa and adjacent omentum resembled those of leiomyomatosis peritonealis disseminata but were confined to the upper abdomen and on further study lacked evidence of smooth muscle differentiation. Although many of these nodules were not resected, a CT scans 3 and 9 months later failed to detect them. This case of GIST in pregnancy is apparently unique and distinct from leiomyomatosis peritonealis disseminata and rare forms of intestinal leiomyomatosis.