OBJECTIVE AND IMPORTANCE: A case report of an extraordinary sellar pituitary tumor composed of corticotrophs and adrenocortical cells is presented. To our knowledge, this is only the second one reported in the literature. CLINICAL PRESENTATION: An 18-year-old female patient presented with amenorrhea. INTERVENTION: Investigations revealed a sellar mass, which was excised transsphenoidally. Histologically, two cell types could be readily distinguished, i.e., small basophilic cells that were positive for periodic acid Schiff and adrenocorticotropic hormone and large cells with abundant, slightly vacuolated, eosinophilic cytoplasm that were negative for periodic acid Schiff and adrenocorticotropic hormone. The nature of the tumor was revealed by ultrastructural examination, thus highlighting the importance of this technique in the investigation of pituitary adenomas. Immunohistochemistry with a panel of steroidogenic dehydrogenases and hydroxylases was positive in the large cells, confirming these as adrenocortical cells. CONCLUSION: We suggest that the designation 'composite silent corticotroph pituitary adenoma with adrenocortical cells' is an appropriate name for this tumor. The explanation for the presence of the two cell types is obscure. Two theories are considered, as were proposed by the authors of the previous case report regarding the same entity (10), i.e., 1) the possibility of misplaced embryonic adrenocortical cells and 2) the presence of uncommitted stem cells that differentiate into adrenocortical cells.
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