Neuronal metaplasia: A pituitary adenoma with gangliocytic component and growth hormone (GH) secretion
Authors: Rotondo Fabio , Amaral Nicole , Munoz David G , Kovacs Kalman , Cusimano Michael D 
Published: June 2021

BackgroundPituitary adenomas (PA) possessing neuronal components are rare. These tumors are usually benign and arise within the sellar region. Most are associated with acromegaly and few with Cushing disease or hyperprolactinemia. Few studies have focused on the origin and presence of neuronal components in the sellar region.Clinical caseA 53‐year‐old woman developed headaches and numbness on one side of her face. Initial work‐up found significant enlargement and/or elongation over the past five years to her hands, feet and face, along with blurred/double vision. She had a history of hypertension, polyuria, and polydypsia. MRI revealed a sellar/suprasellar mass extending toward the cavernous regions and into the chiasm. The lesion was interpreted as a pituitary macroadenoma with mass effect on the optic chiasm and optic nerves.Based on the clinical and radiologic findings, she was diagnosed with acromegalic features secondary to macroadenoma and was started on Octreotide. One month after starting drug treatment the patient underwent transsphenoidal surgery. Morphologic examination of the tissue revealed a homogenous population of predominantly acidophilic tumor cells with focal chromophobic cells. The tumor was admixed with ganglion cells with acidophilic cytoplasm, embedded in fibrillar, neuropil‐like matrix. Immunohistochemistry (IHC) of the tumor, showed intense positivity for GH. Cytokeratin immunostaining showed a distinct pattern of spherical paranuclear fibrous bodies in most cells. Multiple focal areas of neuropil populated with multi‐nucleated Nissl stained ganglion cells were noted. IHC showed that the ganglion cells expressed Hu, as well as variable immunopositivity for multiple pituitary hormones. The neuropil was also positive for neurofilament protein. Microscopic evaluation of the histologic and IHC findings, along with ultrastructural analysis, were characteristic of a sparsely granulated GH‐producing PA with a neuronal component corresponding to neuronal metaplasia.ConclusionAt present, this entity is classified as “ganglicytoma” by the WHO. The name PA with neuronal metaplasia is a more appropriate designation than the other terminologies currently used. Analysis of published data is indicative that such a lesion is likely to have developed from uncommitted progenitor cells within the PA. Metaplasia best explains the presence of transitional cell types as indicated by the histological presence of NFP, Hu, and Nissl with production of multiple pituitary hormones in our sparsely granulated GH‐producing PA. The neuropil herein must have formed from a defective progenitor cell existing within the pituitary tissue. The exact relationship between GH‐producing PAs and the presence of neuronal cells within it is perplexing. The pathogenesis and nosology of PA with neuronal components is not yet fully resolved and further study is necessary to explore the cause, progression and influencing factors of this disease.Support or Funding InformationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.