A Case of Silent Corticotroph Adenoma

Background: Silent Corticotroph Adenomas (SCAs) are tumors with no biochemical or clinical features consistent with hypercortisolism but have positive immunostaining for ACTH. They account for approximately 1.1-6% of all pituitary adenomas and 5.5% of nonfunctioning adenomas. Clinical Case: A 49-year-old woman presented to clinic with a 6-month history of headache, vision changes, fatigue, hair thinning, brittle nails, lightheadedness, polydipsia, easy bruising, increased appetite, and weight gain of 178 pounds in 2 years. Labs obtained: morning cortisol 10 mcg/dl(7-25 mcg/dl), ACTH 59 pg/ml(7.2-63 pg/ml), IGF-1 96 ng/ml(52-328 ng/ml), LH 0.2 mIU/ml(1.9-12.5 mIU/ml), FSH 0.8 mIU/ml(2.5-10.2mIU/ml), alpha subunit <0.1 ng/ml(52-328 ng/ml), TSH 0.991 uIU/ml(0.358-3.74 uIU/ml), free T4 1.12 ng/dl(0.76-1.46 ng/dl), salivary cortisol 66 ng/dl(<100 ng/dl), 24-hour urine cortisol 10 mcg/24hr(3.5-45 mcg/24hr) and prolactin 64.3 ng/ml(2.8-29.2 ng/ml). No hook effect noted with serial dilution. MRI brain showed a 22 x 29 x 26 mm sellar mass extending into the suprasellar cistern displacing and compressing the optic nerves and chiasm superiorly with partial invasion into the right cavernous sinus. She had an endoscopic resection of the sellar mass. She developed diabetes insipidus post-operatively and required desmopressin transiently. In the immediate post-operative period, morning cortisol and ACTH were 16.9 ug/dl(6.2-19.4 ug/dL) 24.8 pg/ml(7.2-63.3 pg/ml) respectively. She was sent home without steroids. Pathology showed a staining pattern consistent with pituitary adenoma with positive staining for ACTH. One month after her surgery she was admitted with symptoms of orthostatic hypotension. Cortisol at 5pm was 3 ug/dl(2.3-11.9 ug/dl), ACTH 31.7 pg/ml(7.2-63.3pg/ml). She had a cosyntropin stimulation test done with peak cortisol of 19.3 ug/dl at 60 minutes. Due to her symptoms, she was started on oral hydrocortisone (HC) for secondary adrenal insufficiency (AI), but was eventually tapered off the steroids. Six months after her surgery, she developed worsening headaches. Repeat MRI obtained showed significant growth of the residual adenoma on the right side of the sella, invading the cavernous sinus. Morning cortisol level of 5.3 mcg/dl(4.3-22.4 mcg/dl) and ACTH level was 11 pg/ml(6-50 pg/ml). She had a repeat endoscopic resection of the pituitary tumor. Her post-surgery cortisol at 2 PM was 3 mcg/dl at which time patient reported symptoms of AI. She was discharged on HC. Pathology again showed a staining pattern consistent with pituitary adenoma with positive staining for ACTH. MIB-1 proliferative index was 5.6%. P53 immunostaining showed a moderate density of moderately intense nuclei in the adenoma. Conclusion: This case illustrates aggressive nature of SCAs with higher risk of recurrence compared to other non-functioning adenomas and therefore requires close follow up.