GH and PRL-Producing Pituitary Adenoma with Neuron-Like Differentiation.

A pituitary adenoma with neuron-like differentiation in the sella turcica is reported. Sections of the tumor showed a mixture of adenoma cells, ganglionic cells, and neuropil-like structures by light microscopy. Both pituitary adenoma cells and large cells recognized as ganglionic cells by H&E were strongly immunoreactive for both growth hormone (GH) and prolactin (PRL), which indicated that these large cells had properties similar to those of pituitary adenoma cells. Furthermore, electron microscopy (EM) revealed characteristic low electron-dense secretory granules as well as GH-type large electron-dense secretory granules in adenoma cells, neuropils, and swollen bulbs of neuronal endings, which indicated that these three populations may be of the same origin. Furthermore, we could not find typical cell bodies of ganglionic cells by EM. These results are consistent with a hypothesis that attempts to explain the origin of the neuronal components by the neuronal differentiation of adenoma cells. Thus, the best designation of our tumor may be "pituitary adenoma with neuron-like differentiation."