Intranuclear rodlets in an intrathyroid tumor associated with hyperparathyroidism.

A tumor excised from the thyroid gland has been shown by electron microscopy to contain distinctive, intranuclear rodlets. This is the first report of such rodlets in a non-neuronal human tumor. While the parathyroid-like hormonal activity, histopathology, and clinical course are consistent with a parathyroid adenoma, the finding of the rodlets raises the question of origin from a special, neuron-related cell of the parathyroid or thyroid. The unusual cellular granularity and the abundant interstitial fibrillae also suggest an unusual cell of origin. Alternatively, a special metabolic activity may account for the rodlets, or they may have been overlooked in prior studies of adenomas.