Ostrovko-cellular tumors of the pancreas

Tumors of the islets of Langerhans were known to morphologists as early as the beginning of the 20th century.

The description of endocrine syndromes became possible only with the discovery of hormones of the pancreas and gastrointestinal tract.

[1], [2], [3]

Epidemiology

To judge the prevalence of islet-cell tumors, there is no precise data. Pathologists one adenoma are found for every 1000-1500 autopsies. In institutions of a broad profile, the ratio of patients with the function of a malignant tumor of the islets of Langerhans to the hospitalized is 1/50 thousand. About 60% of all endocrine pancreatic tumors are insulin secretagogues.

[4], [5], [6], [7], [8], [9]

Pathogenesis

Tumors from islet cells are much less common than other pancreatic tumors. Their classification is based on those clinical manifestations, the development of which they determine, and on the type of cells and hormones that are identified in them, especially immunohistochemistry. A significant portion of these tumors produce a variety of hormones that are found in various tumor cells, but the clinical symptomatology is usually due to one hormone that is biologically active and produced in the greatest amount. Moreover, metastases in a malignant tumor can consist of only one cell type, even with the primary polyclonal tumor. Along with this, there are tumors from a single cell type that produce a variety of peptides. In a number of cases, the clinical and hormonal pattern is due to multiple endocrine pancreatic tumors and / or hyperplasia of islet cells of the same or different types.

It is assumed that there are two sources of origin of endocrine tumors: an islet cell, from which they came to be called insuloma, and a protocol one from multipotent stem cells in the epithelium (nezidoblast) protocol, which can proliferate and differentiate into cells that produce different peptides. These tumors are often the source of ectopic hormone formation. Most often they occur in adults in any part of the pancreas, rarely have their own capsule (especially small ones). Unencapsulated tumors have a so-called zigzag growth, similar to infiltrative. By color and appearance can resemble an extra spleen because of the unusually rich vascularizats j the surface of the cut is homogeneous, grayish-pink or cherry-colored, bleeding and cystic areas are occasionally detected. With severe stromal fibrosis with deposition of lime salts, insulomas acquire a cartilaginous density. The sizes of autonomous tumors range from 700 μm to several centimeters in diameter. Tumors, 2 cm in diameter, are usually benign, and more than 6 cm are malignant.

Solitary or even multiple tumors are often accompanied by development in the surrounding pancreatic tissue of hyperplasia and / or hypertrophy of the islet apparatus, primarily due to beta cells (with insulinomas).

Ostrovkovye tumors are first of all adenomas and less often adenocarcinomas. In size and shape, tumor cells are similar to the corresponding cells of normal islets: polygonal or prismatic, rarely spindle-shaped. In some cells the cytoplasm is eosinophilic, in others it is basophilic, in others - light, and its volume varies from lean to abundant. Nuclear polymorphism is a fairly common phenomenon. In more than half of tumors, the stroma is fibrofected, hyalinized and calcified in varying degrees. About 30% there is amyloid deposition in the stroma. In 15% of cases, psammome bodies are detected, the number of which varies. In 2/3 of the total number of tumors, there are ductal structures and transitional from duct to tumor. The latter form anastomosing cords, nests, rosettes, alveoli, papillary structures separated by numerous thin-walled vessels. Depending on the prevailing structure, there are three types of tumors:

• I - solid, called still diffuse;
• II - medullary, often called trabecular (this type of structure is more common in insulinomas and glucagonomes);
• III - glandular (alveolar or psevdoatsinarny). This type is more common in gastrinomas and in Werner's syndrome. All types of structure can be in one tumor in different parts of it.

Beta-cell tumors (insulinomas) are the most common islet tumors, 90% of which are benign. About 80% of them are solitary. In 10% of cases, hypoglycemia is caused by multiple tumors, 5% of them are malignant, and 5% are non-zidobiosis, for which islet hyperplasia is characterized by their neoplasm from duct cells, islet hypertrophy, caused by hyperplasia and / or hypertrophy of the cells forming it, beta cells. The term non-zidoblastosis was introduced by GF Laidlaw in 1938. It is also characterized by phenomena of acino-insular transformation. Between the clinical manifestations of insulin and their size there is a certain relationship. Immunohistochemically, insulinomas can detect A and / or D-cells, rarely EC cells.

One of the significant achievements of the last two decades in the field of histochemistry and endocrinology is the development of the APUD (Amine Precursor Uptake and Decarboxylation), a concept that allowed to explain the secretion, in particular islet-cellular pancreatic neoplasms, of many hormones not peculiar to its physiological function, so it is not surprising Recent reports on the ability of these tumors to secrete, in addition to the already named hormones, such as chorionic gonadotropin, calcitonin, various prostaglandins, a hormone Ost, antidiuretic hormone, which is an independent role in the formation of any endocrine syndromes completely is not proved, but it is possible that further research in this direction will allow to establish a causal connection between some even well-known diseases of the gastrointestinal tract and pancreas tumors.

[10], [11], [12], [13], [14], [15], [16],

Forms

Currently, the functioning pancreatic tumors are divided into two groups: orthoendocrine, secretion hormones, characteristic of the physiological function of the islets, and paraendocrine hormones that release hormones that are not characteristic of them. The first group includes new growths of alpha, beta, sigma and F cells, which secrete glucagon, insulin, somatostatin and pancreatic peptide, respectively, which is reflected in their name: hence the glucagon,  insulinoma, somatostatinoma and  PPoma. The cellular origin of para- endocrine tumors has not been finally established, it is known only that they are not of P-cell type. These include neoplasms that release gastrin - gastrinoma, vasoactive intestinal peptide - vipoma, ACTH-like activity - corticotropinoma, as well as tumors with a clinical picture of carcinoid syndrome. Paraendocrine also includes some rare tumors secreting other peptides and prostaglandins.

As a rule, neoplasms of the islets of Langerhans, especially malignant, are characterized by polyhormonal secretion, "pure" tumors are a rarity, however, the prevalence of the secretion of a particular hormone leads to the development of a certain clinical endocrine syndrome.

[17],