Teratoma of the pituitary gland in a young male rat.

A pituitary teratoma was found in a 5-week-old (37-day-old) male Donryu rat. The tumour (10 x 11 x 9 mm) was round in shape and white in colour. The cut surface was solid without haemorrhagic or cystic change. Histologically, it was composed of various kinds of tissue components including mature and immature elements derived from the three embryonic germ layers, i.e., nervous tissue, cartilage, bone, squamous epithelial element, glandular element lined by one or more layers of ciliated columnar or cuboidal epithelial cells, striated muscle tissue, adipose tissue and connective tissue. Neuroepithelial rosettes and immature or embryonal epithelium as well as immature cartilage were intermingled with mature somatic tissues.