Case Report & Case SeriesColon metastasis to residual pituitary macroadenoma causing accelerated growth: Case report and review of the literature

•There were 26 reported cases of metastasis to pituitary adenoma (PA).•This is the third case of colonic adenocarcinoma spreading to PA.•This is the forth case with metastasis to residual tumor after previous PA surgery.•Ours is the first case report of colon metastasis to post-ETSS PA.

BackgroundMetastasis to post-surgical pituitary adenoma (PA) is extremely rare.Case descriptionA 53-year-old man previously underwent endoscopic transsphenoidal surgery (TSS) for resection of PA and had stable annual post-operative magnetic resonance imaging for several years. Later, he had abdominal surgery for newly discovered malignant colon neoplasm. In addition, evidence of multiple lung metastases was subsequently discovered prompting chemotherapy. The patient, before his second TSS, presented with symptomatic visual field defect from rapidly enlarging residual PA causing mass effect to optic apparatus. Subsequently, second operation was performed with unremarkable intraoperative findings and postoperative course. However, histopathology revealed metastatic adenocarcinoma inside the PA.ConclusionsThis is the first reported case of metastasis from colon cancer to post-TSS PA.