Collision tumors composed of meningioma and growth hormone-secreting pituitary adenoma in the sellar region: Case reports and a literature review

RATIONALE: Collision tumor is a rare disease that represents the coexistence of two histologically distinct neoplasms in the same area without histological admixture or an intermediate cell population zone. To our best knowledge, 13 cases besides our 2 cases have been reported till now, and our report represents the first publication regarding a collision tumor composed of growth hormone (GH)-secreting pituitary adenoma and sellar meningioma. PATIENT CONCERNS: We collected two cases of collision tumors composed of meningioma and GH-secreting adenoma in the sellar region from 2014 to 2015 at Peking Union Medical College Hospital (PUMCH). DIAGNOSIS: Two cases were diagnosed with solid sellar tumors, and two tumor types were suspected with magnetic resonance imaging (MRI). Blood hormone tests revealed increased insulin-like growth factor 1 (IGF-1) and GH levels. INTERVENTIONS: Both cases underwent transsphenoidal microsurgical resection of pituitary adenoma. OUTCOMES: The tumor was completely resected, and the pathological examination after the operation revealed meningioma and GH-secreting pituitary adenoma. LESSONS: Collision tumors consisting of pituitary adenomas with other sellar neoplasms are rare. Histological examination is necessary because preoperative studies cannot guarantee an accurate diagnosis. If a collision tumor is suspected prior to operation, a craniotomy may need to be considered before other operation methods to avoid reoperation.