To our knowledge, only one case of a TSH-secreting carcinoma has previously been reported. We describe here a second patient with a pituitary carcinoma producing TSH and prolactin (PRL). A 37-year-old male underwent a left frontotemporal craniotomy in 1996 for a sellar mass. Except for mildly increased PRL and elevated α-subunit, hormone evaluation was normal. Pathologic examination revealed a chromophobe adenoma with increased mitotic forms. The patient completed a course of external beam radiation to the pituitary and was prescribed l-thyroxine, bromocriptine, and hydrocortisone. He was lost to follow-up but did well for 6 years, until 2002, when he presented with TSH-dependent thyrotoxicosis and hyperprolactinemia. The patient was started on bromocriptine and propylthiouracil and was, again, lost to follow-up. In 2004, 9 years after his initial presentation, he presented after falling. Magnetic resonance imaging showed two brain masses with associated midline shift. Emergent resection of the larger mass revealed a pituitary cancer with positive staining for PRL, but not for TSH. Nine months later, the patient underwent further debulking of metastatic disease. Although development of a carcinoma from a pituitary adenoma is very rare (<0.5%), macroadenomas that become hormonally active should be suspect for transformation into pituitary cancer.