Morphologic Variations in the Thyroid Glands of Cynomolgus Monkeys (macaca fascicularis)

Abstract

Histologic and morphometric variations in the thyroid glands were investigated in twenty normal Cynomolgus monkeys. Heterogeneity in the pattern of colloid staining and the appearance of degenerating cells were frequently observed in the lumina of the thyroid follicles (45 and 50%, respectively). A few animals showed so-called ‘palpation thyroiditis’, characterized by numerous degenerating cells in the lumina of many follicles accompanied by multi-focal epithelial cell degeneration and interstitial inflammatory reactions. The size of the follicular lumina was different among animals and within an individual thyroid gland. Males usually had larger follicles than females.