Endocrine Abstracts

Pituitary metastasis has been reported in about 6–8% of the breast cancer patients. Diabetes insipidus is the most common initial presentation in metastatic lesions of the pituitary. Anterior pituitary lobe lacks a direct blood supply and involvement usually is due to spread from the posterior lobe. We present a case of a 68-year-old female with known stage IV breast cancer with bone metastasis on trastuzumab, lapatinib and anastrozole who presented with hypotension, lethargy and nausea. Patient had a MRI of the brain that showed abnormal enhancement with intravenous contrast of the anterior pituitary gland and infundibulum. Laboratory work was suggestive of hypopituitarism. Patient was on steroid and thyroid replacement with improvement in symptoms. Patient did not have clinical or laboratory signs of diabetes insipidus. Pituitary biopsy was done that was indicative of metastatic adenocarcinoma of breast origin, with no adenoma or hypophysitis reported. Molecular pathology displayed ER positive, PR negative, HERs/neu positive which was consistent with her molecular pathology from breast biopsy. Further genetic tumor marker testing indicated three PIK3ca variants, pE78Q, pG118D, pD155N. These mutations are reported in squamous cell carcinoma, colorectal cancer, breast cancer, lung cancer and glioma. Patient was also positive for stop codon TP53 variant, pQ331. Germline variants of TP53 has been associated with Li-Fraumeni syndrome and Somatic TP53 variants are seen in various malignancies. Following the biopsy, patient developed increased urination and was hypernatremic to 150 mmol/L and was diagnosed with diabetes insipidus secondary to surgery. Desmopression 0.1mg twice a day was started and sodium level and increased urination improved. Patient is currently undergoing radiation treatment for the pituitary lesion. As diabetes insipidus is the more common presentation in pituitary metastasis, the above case represents an uncommon presentation in a rare form of breast metastasis.