Ultrastructure of mitochondria in various human pituitary tumor types

Abstract

The mitochondria, the major powerhouse for cellular functions, are predominantly ovoid or rod‐shaped cytoplasmic organelles enclosed by double outer membrane. The cristae, are formed by the infoldings of the inner membranes. Morphologic variations in size, shape, number of cristae exist, attuned to the function of the resident organ. Specific ultrastructural features characteristic of certain tumor types may occur. Such mitochondrial alterations were recorded by EM in more than 5000 various types of surgically removed pituitary adenomas. Changes are chiefly quantitative: A) size and density of internal structures (large/small; active/functionally suppressed prolactinoma); B) increase in number, i.e. oncocytic change. Generally occurring within the endocrine system owing to functional decline. Most prevalent in gonadotroph adenomas lineage. Specific alterations: A) giant mitochondria: specific marker of acidophil stem cell adenoma. With preservation of the double membranes, progressive enlargement and disappearance of the internal compartment and occurrence of unidentified tubular structures take place; B) Mitochondrial enlargement and homogenization of the entire internal compartment evident only in gonadotroph adenoma. C) Close spatial association of mitochondria and RER. It occurs only in silent adenoma subtype 3. The specific alterations may be used as ultrastructural markers.