**Islet cell adenoma (or adenoma, or insulinoma)** are benign neoplasms in the pancreas that arise from the endocrine cells of the islet of Langerhans. This is one of the most common perinephric tumors or pancreatectomy (removal of part of the pancreas). In humans they are only small. Pathological cells clog the intercellular ducts and excretory tubules, which leads to an increase in the size of the gland, and over time leads to the development of atrophy of the latter and death within 2-3 years. The processes of the cells merge, replacing them with their own forms in the form of a mass-tumor-lump. Initially, clusters of cells grow in them, forming dendrites; As the islands grow, they connect their internal structures. The shape of the tumor is more characteristic: protrusion into the region of the tail of the kidney. Sometimes it develops in the thickness of the tissue instead of the gallbladder. The risk of recurrence of these neoplasias is low (less than 5%), but more often they are malignant. The following factors increase the likelihood of its development and worsen the prognosis of the disease: age over 60 years, excessive consumption of alcohol or nicotine, exposure to chemical carcinogens, cases of cancer in the family, previous irradiation in the pelvic area. Adenocarcinomas make up 1/2 of all malignant neoplasms of the organ.