Abstract
We examined the histopathological characteristics of ganglion-like cells in relation to C-cell proliferations of the thyroid gland in CD(SD)IGS, CD(SD) and F344 rats. The incidence of the focus being composed of ganglion-like cells was extremely low, between 0.5% and 2.5%, in each strain of aging (approximately 2 years old) rat. The lesions were histologically classified into 2 different types, the complex or ganglioneuroma types. The complex type was observed in 2/367 female F344 rats and 1/290 male CD(SD) rats, and the ganglioneuroma type was observed in 3/122 female CD(SD)IGS rats and 3/290 male and 2/247 female CD(SD) rats. The ganglion-like cells were characterized by abundant cytoplasm with large, eccentric, round nuclei and prominent nucleoli. They were stained positive by Nissl staining and weakly positive by immunohistochemical staining for neuron-specific enolase, but were negative for calcitonin, synaptophysin and neuronal nuclei. Based on these results, we considered ganglion-like cells to be a variation of C-cells, which originate from the neural crest, with a loss of its characterization.
