Surgical indication for pituitary tumors: Functioning pituitary adenomas and Incidentalomas

Abstract

We herewith focus on functioning adenomas and incidentalomas with regard to evaluating candidates for surgery on pituitary tumors. As radical or curative therapies are currently not available for functioning adenomas such as growth hormone (GH)-producing tumor (GHoma), adrenocorticotropic hormone (ACTH)-producing tumor (ACTHoma), and thyroid-stimulating hormone (TSH)-producing tumor (TSHoma), operative therapy is the main treatment. In some cases of GHomas, preoperative administration of somatostatin analogs is useful. High insulin-like growth factor-1 (IGF-1) levels that are often observed immediately after surgery (in spite of normalization of GH) are expected to eventually attenuate with postoperative time, and therefore immediate adjuvant treatment is not necessary. Repeat surgery on residual GHomas localized within the sella turcica is useful when the tumor does not extend to outside the cavernous sinus. As radical medication therapy using dopamine agonists is available for prolactinoma, surgical resection is restricted to exceptional cases. However, medication therapy needs long-term for stabilized management, and surgical resection may have to be executed in cases that experience problems in long-term drug administration, or when tumors develop drug-resistance. In cases of ACTHomas, tumor localization is most critical in performing the surgical intervention. Incidentally found non-functioning pituitary adenomas, especially those with suprasellar extension, may compress the optic chiasm to eventually visual dysfunction. Therefore, surgical intervention is appropriate in these cases. Furthermore, in cases with tumor extension to the anterior cranial base or cavernous sinus, tumor resection becomes difficult, and early treatment is recommended. As for Rathke’s cleft cyst, natural achoresis of cyst is occasionally observed, and the postoperative reaccumulation rate is high, follow-up observations are sufficed so long as pituitary functional impairments are absent. If pituitary function is severely impaired, the damage may become irreversible. Therefore, surgical intervention may be recommended even when only slight pituitary functional impairment is encountered.