Large pituitary adenoma of the sphenoid sinus and the nasopharynx: report of a case with ultrastructural evaluations.

A unique case of nonfunctioning pituitary adenoma exclusively involving the sphenoid sinus and the nasopharynx is reported. The computed tomography and magnetic resonance imaging (MRI) clearly depicted the presence of a large, soft mass in the sphenoid sinus and its extensive invasion to the sphenoid wing and the clivus. In particular MRI was found useful in delineating precise anatomic relationships between this sphenoid sinus tumor and the pituitary fossa. The sphenoid sinus tumor was partially resected by sublabial transnasal approach, and the intact dura mater of the base of the pituitary fossa was confirmed. Pathologic examinations including immunocytochemical and ultrastructural studies showed that the tumor was classified as a nonfunctioning acidophilic pituitary adenoma. Despite the endocrine-inactive tumor, the presence of small secretory granules in the cytoplasm demonstrated by electron microscopic studies was of significant importance in establishing the diagnosis. This rare tumor is reviewed in the literature in the context of nasopharyngeal extension of pituitary adenomas, and a possibility of ectopic occurrence and growth is also discussed in the presented case.