OBJECTIVE To report the first case of 2 synchronous pituitary adenomas, 1 corticotroph and 1 somatotroph, with distinct molecular lineages confirmed by differential hormone and S-100 protein expression. METHODS A case report followed by a literature review are presented. RESULTS A 68-year-old woman presented for evaluation of resistant hypertension. Biochemical testing demonstrated adrenocorticotropic hormone (ACTH)-dependent hypercortisolemia and growth hormone (GH) excess. Pituitary magnetic resonance imaging (MRI) revealed a 2 cm left sellar lesion consistent with a pituitary macroadenoma. The patient therefore underwent transsphenoidal surgery for a presumed cosecreting ACTH and GH macroadenoma. Tumor immunohistochemical staining (IHC) was positive for ACTH, but negative for GH. Postoperative biochemical testing confirmed remission from Cushing disease, but the insulin-like growth factor 1 (IGF-1) level remained elevated. Postoperative MRI demonstrated a small right sellar lesion that, in retrospect, had been present on the preoperative MRI. Resection of the right lesion confirmed a GH-secreting adenoma with negative ACTH staining. After the second surgery, the IGF-1 level normalized and blood pressure improved. Further pathologic examination of both surgical specimens demonstrated differential expression of S-100 protein, a folliculostellate cell marker. Reverse transcription polymerase chain reaction of messenger ribonucleic acid from the left sellar lesion was positive for ACTH and negative for GH, confirming the IHC results. Germline mutations in genes known to be associated with pituitary adenoma syndromes (MEN1, CDC73, CDKN1A, CDKN1B, CDKN2B, CDKN2C, and AIP) were not detected. CONCLUSIONS Although the pathogenesis of synchronous pituitary adenomas has not been fully elucidated, this case report suggests that they can have distinct molecular lineages.