[Mature teratoma of the anterior mediastinum with a predominance of the pancreatic component and signs of focal nesidioblastosis].

A case of a mature anterior mediastinal teratoma with a predominance of the pancreatic component (80% of the tumor) and signs of nesidioblastosis in a 46-year-old woman is presented. During histological examination, all components of the pancreatic parenchyma were determined - acini with interlobular and intralobular ducts, endocrine cells and islets of Langerhans of various sizes and shapes, as well as islet-duct complexes scattered in the acinar tissue. In addition to pancreatic tissue, cartilage, bronchial respiratory epithelium, small intestine tissue, hair follicles, and sebaceous glands were found in the neoplasm. Immunohistochemical examination revealed signs of focal nesidioblastosis. In the islets, insulin-positive β-cells (80.0% of the volume of the islets), as well as endocrine cells expressing glucagon and somatostatin (10.0% of the volume of the islets) were determined. By 2020, only 4 such cases have been published in the English-language literature.