Silent corticotroph adenoma with adrenal cortical choristoma: a rare but distinct morphological entity.

This report describes a case of pituitary adenoma with interspersed adrenal cortical cells. The pituitary cells were confirmed to be corticotrophs with Tpit and adrenocorticotropic hormone immunohistochemistry, whereas the adrenal cortical cells were verified to be such with steroidogenic factor-1 (SF-1), inhibin, calretinin, and Melan A staining. The presence of normal adrenal cortical cells in the heterotopic location of the sella fulfills the definition of choristoma. The origin of adrenal cortical cells within a pituitary adenoma remains unexplained. The important role of SF-1 in both pituitary and adrenal cortex may explain a relationship that supports the possibility of an abnormal proliferation and differentiation of uncommitted mesenchymal stem cells within the sella. However, it remains possible that misplaced adrenal cortical cells derived during embryogenesis give rise to this rare but distinct morphological entity that can pose a difficult diagnostic dilemma. The approach to differential diagnosis is discussed.