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Sunday, May 04, 2008

Gastric Tumors

Gastric tumors may be classified as benign or malignant on the basis of their biologic behavior; epithelial and mesenchymal tumors may be similarly classified on the basis of their origin. More than 95% of malignant tumors of the stomach are adenocarcinomas . The remaining malignant tumors include lymphoma, sarcoma (eg, malignant gastrointestinal stromal tumor), carcinoid tumor, metastasis, and so on. Between 85% and 90% of gastric tumors are benign . About half of these benign tumors are mucosal lesions (mostly hyperplastic or adenomatous polyps) and about half are mesenchymal tumors .
Mesenchymal tumors of the gastrointestinal tract are divided into two broad groups. The first group consists of tumors that are identical to those arising in the somatic soft tissue. These include smooth muscle tumors (eg, leiomyoma, leiomyosarcoma), neural tumors (eg, schwannoma, neurofibroma, plexosarcoma), lipocytic tumors (eg, lipoma, liposarcoma), tumors originating from vascular and perivascular tissues (eg, glomus tumor, hemangioma, lymphangioma), and other tumors . The benign neoplasms in this first group are composed of well-differentiated mesenchymal cells. The second group is far larger and more important and consists primarily of spindle cells or epithelioid cells, which are different from typical somatic soft-tissue tumors and are unique to the gastrointestinal tract. These lesions are called gastrointestinal stromal tumors and constitute the largest category of primary nonepithelial neoplasms of the stomach . Previously, many lesions in this group were erroneously referred to as leiomyoma or leiomyosarcoma .
Although these lesions demonstrate different histologic findings, the overlap of radiologic findings in many gastric tumors makes differentiation difficult. Clinical manifestations also overlap and can vary from severe abdominal pain and acute abdomen to vague signs such as weight loss and anemia. Therefore, some gastric tumors cause diagnostic confusion, which may result in unnecessary surgery or inappropriate follow-up. However, some unusual gastric tumors have characteristic radiologic features that may suggest a specific diagnosis.
Computed tomographic (CT) and barium imaging is often used to diagnose unusual gastric tumors including lipoma, schwannoma, glomus tumor, lymphangioma, Brunner gland hamartoma, carcinoid tumor, and lymphoma. In the CT evaluation of gastric lesions, water is often used as a negative oral contrast agent. Water is particularly well-suited for use as a gastric contrast agent because it has a relatively low attenuation (0–10 HU), which optimizes visualization of the enhancing gastric wall at CT and results in good gastric distention . Adequate gastric distention can be achieved with about 500–1000 mL of water . Find many examples of these tumors at
Abdominal imaging has come a long way for MRI. These images are some that I took of a patient with a tumor in the stomach. We have been able to shorten our scan time to make it possible to aquire nice abdominal images in one breath hold.


MRI Nueroarm Video