Cytoplasmic filamentous masses in chromophobe adenoma of the human pituitary gland.

The fine structure of filamentous masses in three cases of chromophobe adenoma of the pituitary gland is reported. These three were among 18 cases of chromophobe adenoma, 13 non-functioning and five with acromegaly, studied by electron microscopy. All the three cases with fine filamentous masses were adenomas with acromegaly and none of the non-functioning adenomas showed these structures. The cells containing filamentous masses were rich in rough endoplasmic reticulum and poor in secretory granules. These masses were composed of fine filaments and, in some, tubular structures and granules were also present. Prominent RER and sometimes an extensive Golgi system was seen in the adjacent cytoplasm. It is suggested that the filamentous masses arise as a result of degeneration and disintegration of RER and Golgi apparatus.