Pituitary carcinomas, which are rare, generally present with craniospinal and systemic metastases. Although several treatments exist, the prognoses of patients with pituitary carcinomas are extremely poor to date. In this report, the authors describe the case of a 23-year-old male who had undergone trans-sphenoidal surgery and radiotherapy for an invasive prolactinoma. Seven years later, he presented with a new 4th ventricle metastasis from the pituitary lesion, and it was diagnosed with a pituitary carcinoma. He underwent resection and Gamma-knife radiosurgery (GKRS). The tumor has been well controlled for over 3 years. To our knowledge, there have been no reports of the effects of GKRS in patients with pituitary carcinomas. GKRS might have considerable effects in the treatment of pituitary carcinomas.