MON-263 Renal Cell Cancer Metastasis to the Pituitary Masquerading as a Non-Functioning Adenoma

A 47 yr. old male with history of RCC and hypertension was seen in pituitary clinic for management of a pituitary mass. He initially presented to an outside hospital with persistent headaches, unintentional weight loss, severe fatigue, dizziness, cold intolerance, low libido and difficulty with erections. CT head showed a pituitary mass. Lab work revealed pan-hypopituitarism with adrenal insufficiency [random cortisol 0.7 ug/dL (4- 19 ug/dL); ACTH 13 pg/mL (7-63 pg/mL)], hypothyroidism [T4 0.52 ng/dL (0.7-1.5 ng/dL); TSH 0.1 mIU/L (0.45-4.5 mIU/L)] and hypogonadism [total testosterone 15 ng/dL (200-1000 ng/dL); LH of 0.6 mIU/mL (1.5-9.3 mIU/mL); FSH of 3.5 mIU/mL (1.6- 8.0 mIU/mL)]. Prolactin was slightly elevated at 34 ng/mL (2- 18 ng/mL) from stalk compression. IGF-1 was 78 ng/mL (Z score -1.2). When we saw him, he was already on hormone replacement with significant improvement in symptoms. He had no visual field defects or symptoms of diabetes insipidus (DI). As for his history of RCC, he underwent a partial left nephrectomy in 2015, followed by a completion nephrectomy shortly after. Pathology was consistent with clear cell RCC. He did not receive any adjuvant therapy; Follow up imaging studies were reportedly negative for recurrence. Pituitary MRI showed a 1.6 X 1.4 X 1.5 cm enhancing sellar and suprasellar mass without compression of optic chiasm. He was thought to have a presumed non-functioning adenoma, and chose to proceed with trans-spenoidal surgery (TSS). Intra operatively, a very vascular tumor was encountered, which could only be debulked safely. Pathology was consistent with metastatic clear cell RCC. A follow up CT showed innumerable lung nodules and a 3.2 cm right adrenal nodule consistent with metastases. He completed stereotactic radiation to the sella and is currently on Ipilimumab and Nivolumab for immunotherapy. MP is uncommon, and seen in 1-4% of patients with cancer in autopsy studies. Breast (40%) and Lung cancer (25%) are the most common tumors causing MP in women and men respectively, with very few case reports of RCC MP (2.6%). DI is the most common symptom of MP, which is thought to be due to direct vascular supply from hypophyseal arteries to the posterior pituitary. Interestingly in RCC MP, anterior pituitary dysfunction is more prevalent (90%) compared to DI (24%). There is also a tendency for suprasellar extension, causing vision loss. Radiologic features that could help distinguish MP from an adenoma include a rapidly enhancing sellar mass, erosion of sellar floor or posterior clinoid process, infundibular thickening, and the presence of intra-tumoral vascular flow voids. There reportedly is no benefit to using FDG- PET to diagnose MP from RCC. There are no standardized treatment guidelines and the choice of treatment is also influenced by the extent of systemic disease.