Cushing-type ectopic pituitary adenoma with unusual pathologic features

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Ectopic pituitary adenomas comprise, by varying reports, approximately 1-2% of all pituitary adenomas. They are often located in the nasopharyngeal region associated with the pharyngeal pituitary. The location and pathologic features of these masses make them atypical when compared with intrasellar pituitary adenomas. A 54-year-old man presented with vertebral compression fracture and physical stigmata of Cushing’s disease. Biochemical testing confirmed hypercortisolemia responsive to high dose dexamethasone suppression. MRI of the head demonstrated an enhancing mass in the posterior aspect of the sphenoid sinus not involving the sella turcica. Endoscopic biopsy followed by resection confirmed this mass to be a pituitary adenoma with unusual pathologic features. Most notably, the tumor cells demonstrated large, eosinophilic, vacuolated cytoplasm. Immunohistochemical profile of the tumor was typical of an ACTH secreting tumor, notably with positivity for ACTH. The patient did well from his surgery. Post-operatively his serum cortisol level normalized and he remains in chemical remission one year after surgery. Ectopic pituitary adenomas are an unusual manifestation of hormonally active pituitary neoplastic disease. Their atypical clinical presentations, location, and pathologic features can make them a diagnostic challenge. Clinicians should be aware of these entities, especially when considering differential diagnosis for a mass in the sphenoid sinus and nasopharyngeal region. • Ectopic pituitary adenomas frequently arise in the nasopharyngeal region. • These tumors may be associated with the pharyngeal pituitary. • The pharyngeal pituitary is a normal anatomical variant arising in the nasopharynx that may undergo neoplastic transformation. • Ectopic pituitary adenomas frequently have atypical pathologic features, including vacuolar change that may cause them to be mistaken for another, more aggressive tumor type. • In the case presented, electron microscopy was a useful adjunct to identify and diagnose the tumor as an ectopic pituitary adenoma.