A Rare Case of Metastatic Transformation to Pituitary Carcinoma

Background: Pituitary carcinomas are rare and comprise less than 0.5% of pituitary tumors and frequently arise from previously resected and/or radiated infiltrating adenomas.(1) Radiation therapy is used to prevent regrowth but does not have significant data supporting improved prognosis.(2) True pituitary carcinomas requires the presence of craniospinal and/or systemic metastases. Here, we present a case of benign pituitary adenoma that had progressed to a metastatic tumor and responded to radiation therapy. Clinical Case: Our patient was first diagnosed in 1982 with a pituitary mass after undergoing an MRI due to right eye blindness. He ultimately had a transcranial resection of the tumor and post-operative external radiation to residual tumor. Final pathology was consistent with a nonsecretory tumor. Additionally, he was diagnosed with panhypopituitarism and he was treated accordingly. Due to barriers of patient adherence, only one post-operative MRI was obtained, and he was lost to endocrine follow up. In 2007, he was again referred to endocrinology for new vision loss in the left eye. An MRI revealed a 3.0 x 3.8 x 4.4 cm tumor that compressed the optic chiasm. Additionally, multiple lesions were seen within the dural and leptomeningeal extra-axial areas including the largest left frontal lesion of 2.4 cm and a 1.7 cm lesion posterior to the cord within the foramen magnum. The patient underwent endonasal transsphenoidal resection of the sellar mass and biopsy of the frontal lesion in October 2007. Pathology showed pituitary adenocarcinoma in both the sellar and frontal lesions and immunoperoxidase staining was negative for all hormones. He completed salvage radiation to the sellar and craniospinal lesions in December 2007. MRI scans completed 7 months later showed stable residual pituitary and metastatic lesions. The patient received 6-month MRI screening exams for the first 2 years and then annually thereafter, as well as PET scanning, without significant progression or new metastatic lesions. Conclusion: We present a case of benign pituitary adenoma which transformed following resection to a malignant tumor with metastatic lesions in the brain and spinal cord that was treated with radiation with relative success. Despite the often-aggressive nature of these metastatic tumors, the patient has experienced a successful treatment course with minimal side effects and without progression 13 years after initial treatment of the metastatic pituitary carcinoma.