Bilateral extracranial extension of giant somatotropic pituitary adenoma after combined treatment. Two-stage gamma knife radiosurgery as a solution

Abstract Extracranial growth of pituitary adenoma (PA) is very rare and, in the vast majority of cases, is related to invasion of the sphenoid sinus. The unexpected behavior of the tumor, e.g., extension into the subtemporal fossa, can be challenging in practice. We describe the clinicopathological and radiological features of recurrent somatotropic PA with a bilateral extracranial extension after combined treatment (transnasal endoscopic surgery followed by external beam linac irradiation). After 10 years of initial treatment patient still had an elevated serum level of somatotropin and insulin-like growth factor 1 (IGF-1). A CT scan showed the absence of intrasellar lesion but an unexpected invasion of both subtemporal fossae with a maximal size of 40 mm in longitudinal section. We succeeded in tumor shrinkage and in reducing the serum level of somatotropin by two-stage gamma knife treatment.