Adrenocorticotropic Hormone Producing Pituitary Carcinoma in the Falx Cerebri, Retroclival Region, Ethmoidal Cells, and Other Locations.

Pituitary carcinoma is a condition defined by metastasis of a pituitary tumor to a distant location, and it is a very rare type of adenohypophyseal tumor. We present a case of a 29-year-old female who was followed up in our Endocrinology Department. Past medical history included the diagnosis of Cushing disease and transsphenoidal tumor resection at 12 years of age, followed by transcranial resection two years later because of persistently elevated adrenocorticotropic hormone (ACTH). Despite the surgical management, the patient persisted with increased ACTH and hypercortisolism, and, thus, bilateral adrenalectomy was performed a year later. Two years after the procedure, the patient presented with a newly diagnosed pituitary macroadenoma, and the diagnosis of Nelson syndrome was made. Linear accelerator radiotherapy was given, which reduced the size of the tumor. Later, several imaging studies showed multiple lesions on the falx cerebri, posterior clinoid process, retroclival region, cerebellopontine angle, pterygopalatine fossa, infratentorial region, and posterior ethmoidal cells. Biopsy and immunohistochemistry of the falx cerebri lesions described ACTH-producing pituitary adenocarcinoma. Treatment was given with intramuscular octreotide, dabrafenib, and trametinib. Despite persistently elevated ACTH levels, the patient has since remained clinically stable, without new development or worsening of symptoms. There are three unique aspects of our case. First, we reported an unusual presentation of this disease, since the patient in our case was a female with an early age of onset. Second, this is the first reported case demonstrating pituitary carcinoma in the falx cerebri. Third, the prognosis of pituitary carcinoma is usually very poor, and mortality is extremely high; however, the patient in our case has been followed up for seven years since the diagnosis of the metastatic lesions and has remained clinically stable.