Pituitary Gland

Histopathological and immunohistochemical features of proliferative lesions in the pituitary pars distalis of rats

“…As a general interpretation, cellular pleomorphism and atypia are important findings when considering if a tumor has malignant potential. However, in rodent endocrine gland tumors, including pituitary tumors, these findings do not necessarily coincide with malignancy 2 . Therefore, a diagnosis of “carcinoma in situ ” is not applied to small proliferative foci containing atypical cells without boundary or compression of the surrounding parenchyma, and the foci should be diagnosed as focal hyperplasia ( Fig.…”

“…Proliferative lesions derived from the endocrine cells of the pituitary gland, especially those in the pars distalis, are commonly encountered as spontaneous background findings in carcinogenicity studies using various rat strains including Sprague-Dawley (SD), Fischer 344 (F344), and Wistar 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 . It is known that tumors of the pars distalis are a common cause of death in aged rats, especially females 2 , 6 . In fact, a population required for statistical analysis is occasionally insufficient in carcinogenicity studies using rats because many of them are euthanized moribund or found dead due to pituitary tumors.…”

“…Identification of the proliferative cell types is difficult using hematoxylin-eosin (HE)-stained specimens; therefore, immunohistochemical staining needs to be performed although an additional immunohistochemical characterization is usually not performed in standard 2-year carcinogenicity studies 1 , 2 . It is widely accepted that rat tumors of the pars distalis consist mainly of prolactin (PRL)-producing cells and may occasionally also contain other hormone-producing cells including growth hormone (GH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), adrenocorticotropic hormone (ACTH), and luteinizing hormone (LH) sometimes in combination 1 , 2 , 3 , 4 , 9 , 10 , 11 , 12 , 13 , 14 , 16 . It is also known that two or more hormones may be produced from single tumor cells, e.g., PRL and GH 1 , 2 , 9 , 14 .…”

Diagnosis of intracranial neoplasia by transcranial ultrasound in two pet rats (Rattus norvegicus)

“…From the anatomical and functional points of view, the pituitary gland is divided into the adenohypophysis (consisting of pars distalis, pars tuberalis and pars intermedia) and neurohypophysis (consisting of pars nervosa and infundibulum). 1 Hyperplasia and neoplasia of the pituitary gland are common in rats and most frequently affect the pars distalis, with adenoma being one of the most common neoplasms, with reported incidences up to 100% depending on the age, sex and strain. [1][2][3][4] Neoplasms involving other parts of the pituitary gland are uncommon.…”

“…1 Hyperplasia and neoplasia of the pituitary gland are common in rats and most frequently affect the pars distalis, with adenoma being one of the most common neoplasms, with reported incidences up to 100% depending on the age, sex and strain. [1][2][3][4] Neoplasms involving other parts of the pituitary gland are uncommon. Therefore, it seems reasonable to assert that detection of a neoplasm over the sella turcica is highly suggestive of a pituitary adenoma.…”