Cushing’s disease due to a pituitary adenoma as a component of collision tumor: A case report and review of the literature

BACKGROUND: The coexistence of two morphologically different tumors attached to each other creates a very rare type of tumor called a collision tumor. Collision tumors containing pituitary adenoma–sellar meningioma have only been described in four cases to date; we discuss a fifth case harboring a collision tumor comprising a pituitary corticotroph adenoma and a sellar meningioma in the same anatomic position. CASE PRESENTATION: A 34-year-old Caucasian woman presented with menstrual irregularity, severe weakness of the proximal muscles, and 10–15 kg weight gain within a year. Basal plasma cortisol and adrenocorticotrophic hormone levels were 17.7 mg/dL and 58 pg/mL, respectively. Her diurnal cortisol rhythm was impaired (plasma cortisol at 23:00, 18.2 mg/dL) and after a 48-hour, 2-mg dexamethasone suppression test, plasma cortisol level was 13.6 mg/dL. The results were consistent with a diagnosis of Cushing’s syndrome. We then performed a nocturnal 8-mg dexamethasone suppression test and the suppression of cortisol was not greater than 50% (21.4 to 19.3). A pituitary magnetic resonance imaging revealed a tuberculum sellae meningioma arising from within the sellar region. An operation was chosen in order to examine whether the tumor was an adrenocorticotrophic hormone/corticotropin-releasing hormone-secreting lesion or if there were any microadenomas that could be observed during the operation. Via an extended endoscopic endonasal approach the meningioma was resected successfully. Unexpectedly, our patient complained of nausea and vomiting postoperatively. Plasma cortisol was 2.6 mg/dL and orally administered hydrocortisone treatment was initiated immediately. Histopathological examination revealed that the tumor generally consisted of a pituitary corticotroph adenoma infiltrated by meningioma. Our patient maintained hydrocortisone treatment for 11 months. At the latest visit, she had lost 12 kg, and her hypertension, menstrual irregularity, and weakness of the proximal muscles had disappeared. Her mental and physical wellbeing were restored. CONCLUSIONS: To the best of our knowledge, this is the first report of Cushing’s disease due to a pituitary corticotroph adenoma adjacent to a meningioma. Even if a high-dose dexamethasone suppression test fails to suppress basal cortisol level, the importance of considering a suprasellar/sellar meningioma a possible component of a collision tumor presenting as adrenocorticotrophic hormone-dependent Cushing’s syndrome is highlighted here.