Metastasis to the pituitary gland is extremely rare (∼2% of sellar masses). Clinical, biochemical, and radiologic characteristics of pituitary
metastasis are poorly defined and can be difficult to diagnose before surgery. We present an unusual case with pituitary
metastasis as the first manifestation of
renal cell carcinoma (RCC). A 70-year-old male presented with acute onset of weakness,
dizziness,
diplopia, and progressively worsening
headache. The initial CT head revealed a heterogeneous sellar mass measuring 2.8 × 1.9 × 1.7 cm. A follow-up MRI showed the sellar mass invading the right cavernous sinus. The presumptive diagnosis was a pituitary macroadenoma. Physical examination revealed bilateral 6th
cranial nerve palsy and episodes of intermittent
binocular horizontal diplopia. Hormonal testing noted possible secondary
adrenal insufficiency (AM serum
cortisol: 3.3 mcg/dL,
ACTH: 8 pg/mL),
secondary hypothyroidism (TSH: <0.01 mIU/L, FT4: 0.7 ng/dL), secondary
hypogonadism (
testosterone: 47 ng/dL,
LH: 1.3 mIU/mL, and FSH: 2.3 mIU/mL), and elevated serum
prolactin (
prolactin: 56.8 ng/ml, normal: 4.0-15.2 ng/ml).
IGF-1 level was normal at 110 ng/mL (47-192 ng/mL). The patient was discharged on
levothyroxine and
hydrocortisone therapy with plans for close surveillance. However, his condition worsened over the next three months, and he was subsequently readmitted with
nausea,
vomiting, and
hypernatremia secondary to
diabetes insipidus. Repeat MRI pituitary showed an interval increase in the size of the sellar mass with suprasellar extension and a new mass effect on the optic chiasm. The sellar mass was urgently resected via a trans-sphenoidal approach. The
tumor was negative for neuroendocrine markers and pituitary
hormone panel, ruling out the diagnosis of
pituitary adenoma and triggered workup for metastatic
renal cell carcinoma, clear cell type. The diagnosis of
renal cell carcinoma was confirmed by the diffuse and strong staining for
renal cell carcinoma markers (Pax-8, RCC-1, and CD10). A follow-up CT scan noted large right renal mass measuring 11 × 10 × 11 cm. The patient underwent a cytoreductive robotic right radical
nephrectomy for WHO/ISUP histologic grade II clear cell RCC, stage pT2b pNX pM1. He subsequently received fractionated stereotactic
radiotherapy to the pituitary gland. He is presently stable with no radiological evidence of progression or new intracranial disease on subsequent imaging. Pituitary
metastasis most commonly occurs from breast, lung, or gastrointestinal
tumors but also rarely from
renal cell carcinoma. Biochemical findings such as
panhypopituitarism, acute clinical signs such as
headache, visual symptoms, and
diabetes insipidus and interval increase in sellar mass in a short time interval should raise suspicion for sellar
metastasis.