Teaching Case

A 67 year-old male patient was admitted to our institution refering abdominal pain and distention, for one year. At physical examination one could palpate a tender mass, from the epigastric to the pelvic region.

A 67 year-old male patient was admitted to our institution refering abdominal pain and distention, for one year. At physical examination one could palpate a tender mass, from the epigastric to the pelvic region. Ultrasound revealed ascites and an huge cystic mass, multiloculated, extending through the epigastric to the pelvic region, with intracystic papilary projections. The patient underwent nonenhanced CT, because of allergy to the contrast material, which confirmed the alterations noted at US and showed speckles of calcification. The probable site of origin was the stomach but the endoscopy and biopsies were unremarkable. No other changes were noted, particularly, in the parenchymal organs. He was submitted to parcial gastrectomy and the histologic diagnosis was gastric stromal tumor.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasm of the gastrointestinal tract. They express KIT (CD 117), a tyrosine kinase growth factor receptor, which distinguish them from the other mesenchymal neoplasms. The stomach is the site of origin in more than 50%. Most patients are over 50 years old at the time of presentation and the most common symptom is gastrointestinal bleeding. Gastric stromal tumors may be submucosal, subserosal or intraluminal. However, since most of them arise within the muscularis propria of the stomach, they most commonly have an exophytic growth pattern and in barium studies of the stomach they have the classic features of submucosal masses. At CT, GISTs present as a mass, frequently with central areas of low attenuation corresponding to hemorrhage, necrosis or cyst formation. A peripheral enhancement on intravenous contrast-enhanced CT images is present in the majority of patients, and represents peripheral areas of viable tumor. CT is also important to demonstrate adjacent organ invasion, omental and peritoneal spread of tumor or liver metastasis. Calcification, ascites and metastatic lymphadenopathy are unusual findings. One limitation, particularly with very large lesions, is that in many cases the bulk of the tumor will be in an extragastric location, which make it difficult to determine the origin of the tumor. The most important prognostic factors are tumor size and mitotic rate. Therapy is primarily surgical. Imatinib (Glivec), which is a KIT-inhibitor, has shown very promising results for nonresectable tumors, but its exact role has not yet been established.