Gastrointestinal stromal tumor are a group of rare malignant neoplasms of the gastrointestinal tract of mesenchymal origin. Clinical manifestations depend on the localization of neoplasia. There may be a feeling of rapid saturation, pain, bloating, bleeding and intestinal obstruction. In the later stages, weight loss, fever, anemia, hyperthermia and dysfunction of organs affected by distant metastases are detected. The diagnosis is made on the basis of complaints, objective examination data, CT, ultrasound, endoscopic examination and biopsy results. Treatment – surgery, chemotherapy.
General information
Gastrointestinal stromal tumors (GIST) are a group of neoplasms of non-epithelial origin located in the submucosal layer of the hollow organs of the gastrointestinal tract. In 60-70% of cases, the stomach is affected, in 20-30% – the small intestine, in 5% – the rectum, in less than 5% – the esophagus. In some cases, they are detected in the area of the omentum, mesentery and retroperitoneal space, although the mechanism of development of such neoplasms outside the hollow organs has not yet been studied. Gastrointestinal stromal tumor account for less than 1% of the total number of oncological lesions of the gastrointestinal tract. They usually develop after 40 years, the peak incidence occurs at 55-60 years.
At the time of detection, some neoplasms of this group may look benign, but experts always consider such tumors as potentially malignant. Aggressive course is often observed, at the time of diagnosis, 15-50% of patients have metastatic liver or peritoneum lesion. Less often, gastrointestinal stromal tumor metastasize to the bones, pleura and lungs. The main cause of development is considered to be hereditary predisposition. Some researchers point to a connection between the type of mutation and the level of location of neoplasia. Treatment is carried out by specialists in the field of oncology, gastroenterology and abdominal surgery.
Classification
Until the 80s of the last century, experts believed that neoplasms of this group originate from smooth muscle tissue and considered such tumors as leomyosarcomas, leiomyomas and leiomyoblastomas. After the introduction of immunohistochemical techniques and electron microscopy into clinical practice, it was found that the cells of gastrointestinal stromal tumor originate from interstitial Cajal cells, which are a link between the intramural nodes of the peripheral nervous system and the smooth muscle cells of the hollow gastrointestinal organs. One of the main functions of such cells is to coordinate the peristalsis of the esophageal wall, stomach and intestines.
Macroscopically, gastrointestinal stromal tumor are loose soft nodes of pinkish, gray or light brown color with areas of oslizenie. The diameter of the nodes can range from 1 to 35 cm. In the process of growth, such neoplasms can merge, forming conglomerates or cystic structures. Areas of necrosis are usually found in the center of large neoplasms, cystic cavities with hemorrhages are visible in the tissue of neoplasms.
Microscopic examination of a sample of a gastrointestinal stromal tumor reveals fusiform and epithelioid cells located at a distance from each other or grouped into clusters separated by thin layers of connective tissue. Cell polymorphism is noted. Fusiform cells form bundles and whorls. Epithelioid cells have clearer borders, the shape of such cells is rounded or polygonal. The cytoplasm of fusiform and epithelioid cells is light, the cell nuclei are rounded or oval.
Taking into account the features of the histological structure, the following types of gastrointestinal stromal tumor are distinguished:
- Fusiform. They make up about 70% of the total number of stromal neoplasms. Fusiform cells with rounded or elongated monomorphic nuclei predominate.
- Epithelioid. They occur in 20% of cases of stromal neoplasia. Polygonal or rounded cells with oval or rounded light nuclei predominate.
- Ileoform. They make up 10% of all gastrointestinal stromal tumor. Marked cellular polymorphism is noted.
In addition, rare oncocytic, mesothelioma-like and ring-shaped GIST are isolated.
Symptoms
There are no pathognomonic symptoms, the clinical picture is determined by the location of the neoplasm. There may be difficulty swallowing, a feeling of premature satiety, bloating or abdominal pain. In 20% of patients, gastrointestinal stromal tumor in the initial stages is asymptomatic. Due to the non-specificity and mild severity of the manifestations, patients turn to the doctor on average 4-6 months after the first signs of the disease appear. Often such neoplasias become an accidental find during CT, esophagogastroduodenoscopy and other studies. Sometimes gastrointestinal stromal tumor are detected during surgery for another disease.
With the progression of the oncological process, more than half of the patients experience gastrointestinal bleeding, accompanied by melena or bloody vomiting. Many patients develop posthemorrhagic anemia. The high probability of bleeding in GIST is explained by the frequent ulceration of the neoplasm. In 10-30% of patients with gastrointestinal stromal tumor, signs of intestinal obstruction are noted. In the later stages, a decrease in body weight, loss of appetite, weakness and abdominal enlargement due to ascites and / or a growing neoplasm are detected. When palpating the abdomen, a tumor-like formation is determined. With metastasis to the liver, it is possible to increase the organ and jaundice of varying severity.
Diagnostics
The diagnosis is made taking into account clinical symptoms, external examination data and objective studies. Patients are prescribed radiography of the abdominal organs, ultrasound and contrast CT of the abdominal organs. With low-lying tumors, patients are referred for MRI. If the stomach is affected, gastroscopy is performed, if the large intestine is affected, colonoscopy is performed. If a gastrointestinal stromal tumor is suspected of metastasis, chest x-ray, chest CT, spine x-ray, skeletal bone scintigraphy and other studies are performed.
If possible, PET-CT is used to accurately determine the prevalence of a gastrointestinal stromal tumor and to detect small metastases that are not detectable using other techniques. The final diagnosis is established on the basis of histological and immunochemical examination of a tissue sample taken during an endoscopic examination. Differential diagnosis is carried out with other gastrointestinal neoplasms.
Treatment
The main method of GIST treatment is surgical intervention. The volume of the operation is determined depending on the localization and prevalence of neoplasia. The standard is radical resection of pathological foci together with 1-2 cm of surrounding healthy tissues. The removed gastrointestinal stromal tumor is sent for urgent microscopic examination, when malignant cells are detected along the incision line, the affected area is excised.
Due to rare lymphogenic metastasis, lymphadenectomy is not performed (with the exception of gastrointestinal stromal tumor of the rectum, which in 25-30% of cases metastasize to lymph nodes). With single metastases in the liver, radiofrequency thermal ablation or surgical removal of a secondary tumor is performed. In case of inoperable neoplasms, preoperative chemotherapy is prescribed, then a second examination is carried out. When signs of resectability appear, the neoplasm is excised, in other cases, chemotherapy is continued.
The prognosis depends on the location, prevalence and size of the gastrointestinal stromal tumor. The average five-year survival rate is 48%. Up to 5 years from the moment of radical surgery, 50% of patients manage to survive, with tumors with a diameter of more than 10 cm, this indicator decreases to 20%. There is a high probability of recurrence, within 2 years after radical resection, relapses are detected in 80% of patients. According to various data, the average life expectancy for inoperable gastrointestinal stromal tumor ranges from 10 to 21 months.