Gastric lipoma

(One) Etiology

Fat tissue arises in the 14th week of embryogenesis, and the basic structure of fat lobules is formed by the 24th week. The development process of fat cells is divided into four stages: primitive mesenchymal cells, preadipocytes, adipocytes, and mature adipocytes. Fat cells at different stages of development can be found in fat tumors, but they are mainly composed of mature adipocytes.

(Two) Pathogenesis

Gastric lipomas can occur in the gastric body and antrum, with the antrum being more common, 90% originating from submucosal growth, protruding into the gastric cavity to form an intragastric type; 10% grow subserosally, protruding into the abdominal cavity to form an extragastric type.

Grossly, 80% to 90% of gastric lipomas are solitary tumors, 10% to 20% can be multiple, and the tumor is often a sessile spherical mass, can also be lobulated, and a few cases may have a pedicle. Multiple gastric lipomas may have connecting bundles between tumors. The size of the tumor varies, with a diameter of mostly 2 to 5 cm, and larger ones have been reported with a diameter up to 15 cm. The surface of the gastric lipoma is smooth, with a complete capsule, soft to the touch, and can even slide within the gastric wall. The mucosa covering the tumor often develops erosion or ulceration due to mechanical friction, gastric juice damage, or tumor size leading to mucosal malnutrition. The cut surface of the tumor is pale yellow, semi-transparent, soft and delicate, and liquid cavities may form if the fat cells are liquefied.

Under microscopic observation, the tumor is composed of differentiated and mature fat cells, arranged closely, and separated into unequal lobules by fibrous trabeculae. The tumor cells are round, with faintly stained cytoplasm and nuclei located at the periphery. The tumor tissue may contain varying amounts of fibrous tissue or be rich in blood vessels, or associated with mucinous degeneration. If such lesions are present, they can be respectively called fibroadipose lipoma, angiolipoma, and mucinous lipoma. Pathologically, there is a special type of gastric lipoma, where mucosal submucosal scattered muscle fibers are infiltrated with a large number of fat cells under the microscope. Most areas between the mucosa and serosa are composed of fat tissue, with blood vessels easily visible, but without a tendency to form lobular structures, nor any atypicality of tumor cells or nuclear mitotic figures. This is called infiltrative gastric lipoma, and it should be distinguished from gastric liposarcoma.

Gastric lipomas generally have no obvious symptoms, and symptoms appear only when complications occur. When the mucosa on the surface of the tumor can appear erosion or even ulcer formation, patients often have abdominal pain and gastrointestinal bleeding, which is often black stools, and rarely vomiting. Long-term chronic anemia can occur in patients with chronic bleeding.

Upper abdominal discomfort Subtle pain in the stomach Gastrointestinal bleeding

Gastric lipomas generally have no obvious symptoms, and symptoms appear only when complications occur. For those located near the esophagus, difficulty in swallowing may occur; for those located in the pyloric area, complications such as pyloric obstruction symptoms may occur, such as discomfort and pain in the stomach, similar to symptoms of gastric ulcer or chronic gastritis. About 50% of cases may have bleeding. Gastric lipomas occasionally have malignant changes, and large tumors can be palpated in the upper abdomen during physical examination, with soft texture, active movement, and clear borders.

      The etiology of this disease is not yet clear, and it may be related to environmental factors, genetic factors, dietary factors, and emotional and nutritional factors during pregnancy. Therefore, it is not possible to prevent the disease directly by targeting the etiology. Early detection, early diagnosis, and early treatment are of great significance for indirect prevention of the disease. At the same time, although the probability of malignancy is very low, surgical resection is still needed once the disease is found to avoid malignant transformation.

OBT (occult blood test) Barium meal X-ray Immunopathological examination Endoscopic ultrasound

Patients often have gastrointestinal bleeding, manifested as positive occult blood test in feces, and histopathological examination is the basis for diagnosis.

1. Barium meal X-ray examination: Barium meal in the upper gastrointestinal tract can detect tumors with a diameter greater than 2cm, with clear edges, round or oval filling defects. Barium meal can suggest that the mass is located under the mucosa, but cannot distinguish between lipomas and other submucosal lesions. The change in shape of the mass when pressing on the tumor is a characteristic of lipomas, but only larger tumors can show this feature. In addition to the common characteristics of gastric submucosal tumors, gastric lipomas have unique manifestations due to the low density and softness of the fatty tissue:

(1) The defect area caused by the mass is more transparent and has a more distinct contrast.

(2) Deformation: The fatty tumor is soft, and the size and shape of the shadow can change when pressed, and it can even appear intermittently during the filling phase. When the gastric wall muscle layer contracts, it can also compress the tumor, and it is small and elliptical during the contraction phase, while it becomes larger and circular during the relaxation phase.

(3) Displacement: The shadow of the fatty tumor located in the prepyloric area is more likely to be displaced into the bottom of the duodenal bulb through the pyloric canal due to peristalsis, and the pyloric canal also widens at the same time.

2. CT examination: Abdominal CT not only can understand the growth situation of the tumor within the wall, but also can measure its CT value, understand the tissue structure of the tumor, achieve the purpose of clear diagnosis, has certain diagnostic value, can distinguish fat from other tissues, and there are several cases reported with confirmed diagnosis by CT.

3. Endoscopic diagnosis: Endoscopic examination is a relatively accurate diagnostic method with a high positive rate, but attention should be paid to differentiate it from extragastric masses. Under the microscope, a smooth, yellow or orange, soft mass is seen, the mucosal elasticity of the tumor surface is poor, and it is not easy to shrink after being pulled by biopsy forceps, forming a tent sign. When pressing on the tumor, a depression is formed, like a sponge. Conventional biopsy cannot reach the tumor under the mucosa, and deep biopsy using electrocoagulation is required to obtain tumor tissue. Sometimes ulcers can be seen on the surface of the tumor. When the elevated part covers the normal mucosa and ulcers form, it needs to be differentiated from cancer. Those less than 2cm are mostly ectopic pancreas, carcinoid, or myogenic tumors, and lipoma is very rare. When it is difficult to determine the nature of tumors larger than 2cm by biopsy, Ritsugu Saito et al. use neodymium-yttrium-aluminum-garnet (Nd-YAG) laser or ethanol to cause ulcers, and then take biopsies from the deep part of the ulcers. Even so, there may still be missed or misdiagnosed cases, so the routine use of ultrasound endoscopy is very necessary.

4. Endoscopic ultrasound: It can detect submucosal diffuse hyperechoic masses and is also helpful for diagnosis.

I. Diet

1. Abstain from alcohol and alcoholic beverages, reduce the intake of spicy foods such as chili and dog meat, as刺激性 foods can promote the growth of lipoma, so these foods should be eaten less.

2. Maintain regular eating habits, with breakfast at 30% of the daily food intake, lunch at 40%, and dinner at 30% of the daily food intake, which is relatively reasonable.

3. Reduce the intake of high-cholesterol foods such as egg yolks, fatty meats, seafood, scaleless fish, and animal内脏, etc.

(I) Treatment

Cases without symptoms may not require treatment, but due to the difficulty of preoperative diagnosis of the disease, most cases require surgical resection to exclude malignant lesions. The surgical method is determined according to the specific condition of the lesion, and local resection of the tumor or wedge resection of part of the gastric wall can be performed. For multiple tumors, partial gastrectomy can be performed. If there is a suspicion of malignant transformation, frozen section examination should be performed during surgery, and the extent of resection should be determined according to the nature and location of the lesion. Recently, there have been reports of resecting polypoid tumors through endoscopy. Smaller tumors can be locally resected or simply removed, while larger ones require partial gastrectomy.

(II) Prognosis

The prognosis of gastric lipoma is good, and there have been no reports of malignant transformation into sarcoma.