BENIGN TUMORS OF THE STOMACH
Benign tumors, compared with carcinomas, are relatively rare. They are small and typically do not cause symptoms. With the increasing use of endoscopy and radiologic imaging, small tumors are now more frequently detected incidentally.
Benign tumors are classified as epithelial, submucosal, or ectopic, based on the tissue layer of origin. Epithelial tumors include hyperplastic, fundic gland, and adenomatous polyps. Submucosal tumors include gastrointestinal stromal tumors (GISTs), leiomyomas, lipomas, fibromas, hamartomas, neurofibromas, hemangiomas, eosinophilic granulomas, and inflammatory polyps. Ectopic tissue of the pancreas, called a pancreatic rest, or Brunner gland hyperplasia can lead to benign tumors in the stomach.
Benign tumors are rarely symptomatic. They are most commonly detected when an endoscopic or radiologic examination is performed for another indication. If a benign tumor does enlarge and is located near the pylorus, it may cause symptoms of obstruction. These tumors can chronically bleed, leading to a clinical picture of anemia or acute upper gastrointestinal bleeding. These tumors rarely produce epigastric pain. In such cases, upper endoscopy is needed to distinguish a benign tumor from peptic ulcer disease.
If a tumor is first identified on radiography, barium contrast, computed tomography scanning, or magnetic resonance imaging, the next best diagnostic test is upper endoscopy with biopsy. Biopsy can help with making a histologic diagnosis. Upper endoscopy can also be therapeutic, with complete removal of the benign tumor. The tumor will often require further evaluation with endoscopic ultrasound (EUS). EUS identifies the depth of the lesion and the tissue layer of origin, which is most useful for confirming a diagnosis of subepithelial tumors.
The most important clinical significance of benign tumors is their malignant potential. For this reason, endoscopy with either biopsy or complete resection is necessary. Fundic gland polyps, which arise from the epithelial layer, have become more common with the widespread use of proton pump inhibitors. They only carry malignant potential if familial adenomatous polyposis syndrome is present. Once the histologic diagnosis of fundic gland polyp is confirmed after upper endoscopy with biopsy, and the syndrome is not present, no further therapy or surveillance is needed. Hyper-plastic polyps are also epithelial, but in contrast, do have an increased risk of developing into gastric cancer, especially if they are larger. The recommendation is that all polyps be at least biopsied, and larger ones should be completely resected.
The gastric adenoma, sessile or pedunculated, contains more or less regular epithelial tubules embedded in loose connective tissue. The pedicle of such a solitary “polyp” of the stomach usually is broad where it attaches to the gastric wall, but the stalk is thin and permits free mobility of the tumor. If the tumor is in front of the pylorus or is pushed in front of it by peristalsis, intermittent partial obstruction may result. The pendulous, to-and-fro movements can give rise to irritation and stretching of the tumor’s mucosa, which can lead to epigastric pain and bleeding. In some cases, recurrent or profuse hematemesis may be the first clinical manifestation.
Adenomatous polyps tend to be larger than fundic or hyperplastic polyps and may develop into gastric cancer.
Once the diagnosis of gastric adenoma is made, the polyp should be completely endoscopically resected. A technique called endoscopic mucosal resection may be required to ensure that the entire adenoma is removed. This requires injecting saline into the mucosa to lift the lesion. After the polyp has been completely removed, the patient will require follow-up endoscopy to confirm that the adenoma has not recurred.
Numerous polyps throughout the gastrointestinal tract are seen in familial polyposis syndromes. These are usually fundic gland polyps but can also be adenomas, both of which may develop into gastric adenocarcinomas. These patients therefore require routine surveillance with upper endoscopy. Hamartomatous polyps or hamartomas are seen in Peutz-Jeghers syndrome and in juvenile polyposis. These polyps, found in the stomach and small bowel, do carry a small risk of malignant transformation, and these patients therefore also require routine surveillance with upper endoscopy.
GISTs are the most common type of mesenchymal stromal gastric tumors and arise from the smooth layer. They are typically slow growing, presenting in the fifth or sixth decade of life with abdominal pain or bleeding. Their malignant potential is based on their size and the mitotic index, the latter of which can only be deter-mined after resection. EUS helps to confirm whether the lesion arises from the subepithelial layer, and fine-needle aspiration can provide a histologic diagnosis. EUS will also identify the depth of involvement and any lymph node involvement. Cytology samples show spindle cells, and immunohistochemistry can confirm the diagnosis. A smaller confirmed GIST should be closely monitored with repeat EUS, whereas larger GISTs and those causing symptoms such as pain or bleeding should be completely removed.
|Plate 4-59 |
BENIGN TUMORS OF STOMACH
Lipomas are common benign tumors that can be seen in the stomach as well as other parts of the gastrointestinal tract. They are slow-growing tumors that are usually incidentally found on upper endoscopy. Depending on their size and location in the stomach, they can cause abdominal pain, bleeding, obstruction, or intussusception. On endoscopy, they appear as smooth, yellow, subepithelial lesions that are soft when gently probed with a closed biopsy forceps (pillow sign). Histology shows deposits of adipose tissue in the wall of the gastrointestinal tract. They do not have malignant potential, and there are no current recommendations for resecting all lipomas.
The leiomyoma belongs to the group of smooth muscle tissue tumors which include such mixed tumors as fibromyoma, adenomyoma, and others. Histologically, the gastric leiomyoma possesses the same characteristics as myoma does elsewhere in the body. It is usually well encapsulated and grayish-white on the cut surface; it originates from the muscular layers and develops below or within the submucosa. In extremely rare cases such a leiomyoma may enlarge through the serosa to form an extragastric tumor. Intragastric tumors may attain such size as to occupy a large part of the lumen. In such instances, they may cause obstruction, or at least serious impairment, of the filling and emptying of the stomach. Smaller tumors, occasionally multiple, usually have no clinical significance. The mucosa above a large leiomyoma is stretched tightly and tends to ulcerate and, subsequently, to bleed profusely. In addition, the tumors may, rarely, undergo degeneration.
Neurofibroma is a slow-growing neoplasm, usually originating from a nerve sheath coursing along the lesser curvature. The tumor may also occasionally represent part of a generalized neurofibromatosis (neurofibromatosis type I or von Recklinghausen disease). A neurofibroma may expand in the direction of the lumen and may produce there a submucosal protrusion, or it may project outward into the peritoneal cavity, in which case it may sometimes become pedunculated. Provided the mucosa is sufficiently stretched, intragastric neurofibroma may also give rise to bleeding, as do other benign tumors. If not, they display few, if any, clinical symptoms. Cystic degeneration of a neurofibroma has been reported.
Another rare benign tumor of the stomach is a hemangioma (not illustrated). Its specific characteristic is the marked tendency to cause bleeding.