Pituitary Metastasis From Breast Cancer Presenting as SIADH

Abstract

Pituitary metastasis is rare and unusual but can be seen in advanced breast and lung cancers with patients presenting with symptoms that range from mild headaches to seizures and altered mental status due to hyponatremia. A 53-year-old female with invasive ductal carcinoma of the left breast which was hormone positive, presented 5 years after completion of therapy with a dry cough, hyponatremia, weakness and visual disturbance. An MRI of the brain revealed a pituitary mass, compressing the optic chiasm. Hyponatremia was found to be due to SIADH. Biopsy confirmed metastatic breast carcinoma. Metastatic spread to the pituitary gland is rare (comprising less than 1% of pituitary tumors) but can occur in patients with advanced breast and lung cancers. Presentation with SIADH has previously not been reported with metastases due to breast cancer. Diagnosis may require biopsy or resection of the pituitary. Despite aggressive intervention, the prognosis is poor.