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.
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| Plate 4-58 GASTRIC POLYPS |
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.
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| 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.
