Somatostatinoma is a rare hormonally active neoplasm originating from delta cells of the islets of Langerhans located in the pancreas, less often from cells of the diffuse neuroendocrine system localized in the duodenum. It is manifested by pain, dyspepsia, steatorrhea, weight loss and anemia. It is accompanied by the development of diabetes mellitus and cholelithiasis. In the later stages, somatostatinoma usually metastasizes to the liver. It is diagnosed on the basis of clinical symptoms, laboratory tests, CT, ultrasound and other studies. Treatment – surgical resection, chemotherapy, symptomatic therapy.
Information
Somatostatinoma is a rare tumor originating from the cells of the APUD system that produce somatostatin. In 90% of cases, it shows signs of malignancy. In 60% of cases, it is located in the pancreas, formed from the delta cells of the islets of Langerhans. 35-38% of cases are due to somatostatinomas, the source of which are enterochromaffin cells of the small intestine (usually the duodenum). It was first described in 1977. To date, there are only a little more than 20 descriptions of somatostatinoma in the specialized literature, so the patterns of development of this disease remain insufficiently studied.
It has been established that the development of pancreatic somatostatin is usually accompanied by fairly vivid clinical symptoms, and duodenal neoplasia is prone to a low-symptomatic or asymptomatic course due to less active somatostatin production. A combination of somatostatinoma and MENG-II syndrome is possible. Women suffer more often than men. The treatment is carried out by specialists in the field of oncology, endocrinology, gastroenterology and abdominal surgery.
Classification
In clinical practice, the classical four-stage classification of oncological diseases and the TNM classification are used. According to the four–stage classification, the following stages of somatostatinoma are distinguished:
- Stage 1 – a node with a diameter of less than 2 cm is detected, well delimited from the surrounding tissues. There are no metastases.
- Stage 2 – the diameter of the somatostatinoma exceeds 2 cm. There are no metastases.
- Stage 3 – neoplasia of any size with metastases to regional lymph nodes is detected.
- Stage 4 – a neoplasm of any size with metastases to distant organs is detected.
According to the TNM classification, the following stages of somatostatinoma are distinguished:
- T1 – neoplasia does not extend beyond the pancreas, while T1a – node diameter is less than 2 cm, T1b – more than 2 cm.
- T2 – somatostatinoma sprouts the surrounding fiber, bile duct or duodenum.
- T3 – the neoplasm sprouts the colon, stomach or spleen.
The letter N denotes lymphogenic metastases (N0 – no metastases, N1 – there are metastases), the letter M – distant metastases (M0 – no metastases, M1 – there are metastases).
Symptoms
Somatostatinoma is characterized by a triad that includes cholelithiasis, favorably occurring diabetes mellitus and steatorrhea. Along with the listed signs, patients may experience pain and discomfort in the upper abdomen, diarrhea, hypochlorhydria, anemia and weight loss. The listed symptoms of somatostatinoma are directly or indirectly caused by the action of somatostatin. The cause of the development of diabetes mellitus is a slowdown in the release of insulin by beta cells in combination with inhibition of glucagon release by alpha cells of the islets of Langerhans.
The high probability of gallstone disease in patients with somatostatinoma is explained by a decrease in the contractility of the gallbladder with an increase in the level of somatostatin. The release of a large amount of fat with feces is due to impaired secretion of pancreatic enzymes and deterioration of absorption in the intestine. A decrease in the acidity of gastric contents in somatostatinoma is a consequence of the suppressive effect of somatostatin on acid-forming cells and G-cells of the stomach.
With the progression of somatostatinoma, common symptoms of cancer are revealed. Patients suffer from weakness, fatigue, mood disorders, mental retardation and sleep disorders. Patients with somatostatinoma experience loss of appetite, weight loss up to cachexia, pallor and dry skin, sweating, hyperthermia, nausea, vomiting, anemia and immune disorders. A characteristic feature is frequent metastasis to the liver, accompanied by jaundice and hepatomegaly.
Diagnostics
The diagnosis is made taking into account complaints, anamnesis of the disease, the results of laboratory and instrumental studies. Patients are prescribed a blood test to determine the level of somatostatin and tests with prior stimulation with drugs with hypoglycemic effect. In the presence of somatostatinoma, the level of somatostatin is hundreds or even thousands of times higher than normal (50-100 pg /ml), induced hypoglycemia is accompanied by an increase in the level of somatostatin.
To assess the location, size and prevalence of somatostatinoma, MRI of the pancreas, ultrasound of the pancreas, ultrasound of the abdominal cavity and MSCT of the abdominal organs are performed. To detect liver metastases, ultrasound, CT and MRI of the liver are performed. When somatostatinoma is located in the duodenum, it is possible to use endoscopic ultrasound. Differential diagnosis is carried out with other neuroendocrine tumors, diabetes mellitus, cholelithiasis, as well as diseases accompanied by diarrhea and steatorrhea.
Treatment and prognosis
The main method of treatment of somatostatinoma is pancreatic resection. In the postoperative period, chemotherapy drugs are prescribed (5-fluorouracil, streptozocin, doxorubicin, dacarbazine). With somatostatinomas at the stage of distant metastasis, chemotherapy is performed. In addition, patients are prescribed symptomatic therapy. Drugs containing pancreatic enzymes, oral hypoglycemic agents, analgesics, antiemetics, etc. are used. Hepatoprotectors are used to protect the liver. A special diet is recommended.
The prognosis for somatostatinoma is determined by the prevalence of the oncological process. In the absence of metastases, the five-year survival rates approach 100%. With lifogenic metastases and distant liver metastasis, 30-60% of patients manage to survive up to 5 years from the moment of diagnosis. Since most patients have foci in the liver and regional lymph nodes at the first treatment, somatostatinoma is usually considered as a prognostically unfavorable disease.