Insulin is produced by the pancreatic β cells in the islets of Langerhans. Between approximately 2/3 and 3/4 of adult pancreatic cells are producers of insulin.
In the normal adult pancreas, the islets of Langerhans do not exceed a diameter of 300µm. In inflammatory or fibrotic processes the islets can be enlarged and can also be aspherical. When the islets exceed a diameter of 500µm they are referred to as “micro adenomas” and the possibility of genetic diseases such as MEN 1 (Multiendocrine neoplasia I) must be considered. In non tumoral islets the insulin producing cells are uniformly distributed over the entire islets and are very abundant. Glucagon producing cells have the tendency to be distributed peripherally although they can also be found in the interior of the islets.
Somatostatin producing cells are the most scarce and do not demonstrate any preference of localization. Some somatostatin producing cells can have a fusiform morphology.
We rarely encounter Gastrin and VIP (Vasoactive intestinal peptide) producing cells in the pancreatic islets and for this reason these hormones are considered ectopic to the pancreas. Although some patients have pancreatic gastrinomas and vipomas, their localization most frequently is in the duodenum.
It is more probable that benign pancreatic endocrine tumors clinically present a functional syndrome due to the peptide that they produce while malignant tumors will only rarely display a functional syndrome.
Both benign and malignant pancreatic endocrine tumors show a diversity of cells producing diverse peptides including insulin, glucagon and somatostatin, but they frequently express one of these peptides in a greater quantity than normal. Non tumoral islets of Langerhans will express this peptide at a much lesser intensity probably due to the inhibitory feedback phenomenon.
In some cases of pancreatic non-functional endocrine tumors, these tumors have been immunohistochemically found to have an absence of a protein although the RNA for this protein is present. Therefore in situ hybridization is a much more useful technique for studying this kind of tumor and their metastasis.
For use in In Vitro Diagnosis.
The Kit Histosonda Somatostatin is useful for the study and classification of neuroendocrine tumors of the pancreas and digestive apparatus and their metastasis even in an absence of a clinically evident Endocrine Syndrome.
WARNINGS AND PRECAUTIONS
The Kit Histosonda Somatostatin has been designed for professional use in In Vitro Diagnosis and must be manipulated by qualified and accordingly trained personnel.
In order to obtain the best results, the instructions contained in the manual must be followed. Any change to the indicated temperatures, times or any other step of the process can lead to poor results.
The Kit includes 20 single test tubes of Histosonda Somatostatin; 20 single test tubes of Proteinase K and 2 tubes of Anti-Digoxin antibody sufficient for 20 tests in total. All products are lyophilized.
Histosonda Somatostatin consists of a fragment of single-stranded DNA with a length of 302 nucleotides complementary to expressed RNA. These probes have been labeled with Digoxigenin.
Supplied reagents are stored at room temperature until their expiration date. After being reconstituted the probes will remain stable for two weeks at 4ºC in a DNAase-free environment. The Anti-Digoxin can be stored at 4ºC for 1 month and the Proteinase K must be used immediately and cannot be stored. Do not use these products after their expiration dates.
Any paraffin block section in which somatostatin RNA presence is to be studied. Sections of 4-6 micrometers in width are sufficient to conduct the study. Preferably, the cut should be recent (no more than thirty days old). Assay results are not affected by block age. Studies have been carried out in the manufacturer's laboratories using 20 year old paraffin blocks with optimal results.
INTERPRETATION OF RESULTS
Samples in which somatostatin expression is observed will show a brownish color in the cell cytoplasm, which will contrast over the blue-violet background given by hematoxylin staining. The pathologist will evaluate the results according to their experience, drawing conclusions from the staining of the sample in parallel with the staining observed in positive and negative controls.
The Kit Histosonda Somatostatin has been optimized to detect RNA expression in formalin-fixed, paraffin-embedded tissues. Its use is not recommended for other types of samples or preparation techniques.
The correct operation of this kit has been validated using the protocols indicated in the instructions manual. The use of other procedures or the modification of the recommended protocols may lead to erroneous results.
The results from this assay must be evaluated by the pathologist in combination with the rest of available patient clinical data.
In order to obtain optimal and reproducible results it is important to rigorously maintain the time and temperature conditions indicated in the procedure.