What happened, in summary

A 41-year-old Chinese woman had a history of right breast cancer treated 1 year earlier with mastectomy and chemotherapy. The prior breast cancer was invasive carcinoma of no special type with mucinous features, but the initial breast-cancer stage was not stated. She first presented to a local hospital after 3 months of frailty, nausea, and vomiting and was diagnosed with hyperthyroidism, treated with methimazole tablets. Two months later, she was referred for significant vision loss that affected daily life. MRI showed a sellar-region lesion measuring about 23 x 20 x 16 mm, compressing the pituitary stalk and optic chiasm. The lesion was initially considered a benign pituitary macroadenoma. Laboratory findings included elevated CA125 and hypothyroidism. She underwent surgical resection of the pituitary mass. The gross specimen was a grey-white hard mass measuring about 10 x 5 x 5 mm. Intraoperative frozen biopsy was initially interpreted as benign pituitary macroadenoma, but permanent pathology and immunohistochemistry changed the diagnosis. The pituitary lesion was metastatic breast cancer, with GATA3 positivity, ER 2+ in 75% of cells, PR 1+ in 5%, and HER2 0. After surgery, she received antibiotics, hormone replacement/supportive therapy, and electrolyte maintenance. She recovered well and was discharged after 2 weeks. At 11 months after surgery, she remained disease-free. No additional systemic breast cancer treatment was described after the pituitary surgery. No recurrence or systemic progression was described during the 11-month follow-up, making the outcome disease-free after local treatment of the pituitary metastasis. Her neurologic presentation was therefore resolved surgically despite an initially benign-appearing sellar mass.