Pituitary adenoma-neuronal choristoma is a pituitary adenoma with ganglionic differentiation

The presence of ganglion cells within an endocrine pituitary tumor has been named hamartoma, choristoma, gangliocytoma, or most recently pituitary adenoma-neuronal choristoma (PANCH). The presence of neuronal differentiation in regular pituitary adenomas has been previously suggested, however, its origin, the extent of its presence, and the relationship between the neuronal elements and the pituitary adenoma remain uncertain. Thus, to further explore the neuronal potential of pituitary tumors, we used immunohistochemistry on pituitary tumors of different grades, with a neuronal antigen protein (NeuN) antibody as a specific marker for mature neuronal differentiation. We found NeuN expression in 26.47% (9/34) cases of pituitary tumors without ganglionic differentiation (7 adenomas, 1 atypical adenoma and 1 pituitary carcinoma), in addition to NeuN expression in pituitary adenomas with ganglionic cells (2/2). Thus, neuronal expression is an innate property of pituitary adenomas. We propose that the rare presence of ganglionic cells in pituitary adenomas is not the result of a separate lesion or "collision sellar tumors", as previously suggested, but a ganglionic neuronal differentiation in an endocrine neoplasm. The ganglionic cells may be arising from uncommitted stem/progenitor cells that contain both neuronal and endocrine properties. A label of "pituitary adenoma with ganglionic differentiation" would better reflect the dual differentiation in a neuroendocrine tumor than the current label "PANCH".