Pituitary tumorigenesis in aging female C57BL/6J XXXX : a light and electron microscopic study.

@entity19 @entity1184 @entity5 @entity977
Spontaneous @entity977 have been studied by light and electron microscopy in female C57BL/6J @entity19 at 2 1/2, 11, 15, 22, 23, 24 and 30 months. @entity5 were evident macroscopically in greater than 50% of @entity19 22 months or older, and greater than 80% on microscopic evaluation. Active and hypertrophied mammotrophs were the predominant cell type within the @entity5 at 22-30 months, often totally filling large portions of the @entity5 mass. Exocytosis of secretory granules was extensive from the mammotrophs, but much less abundant from other parenchymal cells. Somatotrophs and gonadotrophs were also present, and appeared active and often strikingly hypertrophied. The @entity5 were characterized by disruptions of parenchymal and capillary integrity which resulted in the formation of large vascular lakes lined solely by @entity5 cells, generally mammotrophs. Apparent metastasis of @entity5 cells into the vascular lakes was also observed. In 11- and 15-month @entity19 small @entity5 or pretumor foci were evident in some @entity19 on microscopic evaluation, although they were not visible macroscopically. Their degree of development was somewhat variable, but they had essentially the same features as more advanced @entity5 in older @entity19 . pretumor foci were characterized by more moderate disruptions of parenchymal cell and capillary integrity; cellular @entity1184 , particularly of somatotrophs and gonadotrophs; and the presence of small vascular lakes. In 2 1/2-month @entity19 @entity5 could not be localized macroscopically or microscopically, and the pituitary was composed of well-defined cell cords and an intact capillary bed. However, small focal zones of capillary and tissue disruption were apparent occasionally in 2 1/2-month @entity19 . These findings indicate that the process of pituitary tumorigenesis in female C57BL/6J @entity19 is initiated by midlife, with subsequent progressive development into large, mammotroph-dominated @entity5 .
