PMON94 Collision tumor with Rathke cleft cyst and co existing Cushing's disease

Abstract

Abstract Introduction - Collision tumors, i.e., co-occurring distinct histopathological lesions are rare. We present a case of a 48-year-old female present with co-existing Rathke cleft cyst (RCC) and pituitary adenoma with Cushing disease. Case - 48-year-old female presented for evaluation of an incidental sellar mass with enlarged pituitary noted on MRI brain. The patient complained of symptoms of mental fogginess, confusion, intermittent dizziness for the last 1 year. The patient had complained of easy bruising with no reported weight gain, change in facial appearance, proximal muscle weakness. MRI brain showed mildly enlarged pituitary measuring 13 mm with RCC.Past medical history was significant for recent-onset Type 2 Diabetes and Hypertension. The examination was unremarkable with no signs of Cushing's syndrome. Lab work showed elevated ACTH of 51 pg/ml (10-48) with AM cortisol level of 14.7 mcg/dl (6- 18.4). IGF-1 levels elevated at 307 ng/ml (77- 220). LH, FSH, FT4, prolactin levels were normal. Given elevated ACTH levels, further testing showed elevated midnight salivary cortisol at 0.22 and 0.239 mcg/dl (0.010-0.090), elevated 24-hour urine cortisol 141 ug/ 24 hrs. (6- 44), absence of suppression with 1 mg dexamethasone with cortisol 12.4 mcg/dl (< 1.8), ACTH 123 pg/ml (10-48) with dexamethasone levels 432 ng/dl (140- 295). Lab work was consistent with ACTH-dependent hypercortisolism. MRI pituitary showed 7.5×7.8 mm RCC.8 mg dexamethasone suppression test and CT chest, abdomen, and pelvis were performed to differentiate between ectopic Cushing's and Cushing's disease. Cortisol levels suppressed greater than 50% after 8 mg dexamethasone from baseline cortisol – 17.7 mcg/dl and ACTH 67 pg/ml to cortisol 3.4 mcg/dl and ACTH – 34 pg/ml with dexamethasone levels of 3120 ng/dl (1600–2850). CT chest abdomen, pelvis showed no evidence of bronchial carcinoid or other potential lesions. With neuroimaging findings and biochemical confirmation of Cushing's disease, the patient underwent transsphenoidal resection. Discussion – The association between RCC and pituitary adenoma was found in 0.5–1.9% cases per literature review1, co-occurrence with ACTH producing pituitary adenoma being rarer. The diagnosis of collision tumors can be challenging as the most common presentation on imaging is a cystic mass. Appropriate biochemical testing is indicated based on clinical presentation, initial laboratory testing, and level of suspicion. Elevated ACTH levels along with diabetes and hypertension led to a diagnosis of Cushing's disease in our patient with the initial presentation of an incidental RCC. The knowledge about collision tumors is important, especially in unusual presentations as in our case. References Sagan KP et al. Cushing's Syndrome in a patient with Rathke's cleft cyst and ACTH cell hyperplasia detected by 11C-Methionine PET Imaging-A Case Presentation. Front Endocrinol (Lausanne). 2020; 11: 460. Published 2020 Jul 22. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.