Pituitary Metastasis as the Initial Manifestation of an Undiagnosed Adenocarcinoma of Mullerian Origin: A Case Report and Literature Review

Metastasis to the pituitary gland is rare, occurring in approximately 1% of pituitary tumors resected via transsphenoidal surgery. We present the second report of metastatic high-grade serous ovarian carcinoma to the pituitary gland, presenting with diabetes insipidus and bilateral hemianopsia. An 86-year-old female patient presented with complaints of dizziness, vertigo, vision changes (peripheral field vision loss), loss of taste, extreme thirst, and fatigue. Urine studies revealed hypotonic hyponatremia, which was consistent with diabetes insipidus. The pituitary magnetic resonance imaging (MRI) scan revealed a sellar and suprasellar hypoenhancing lesion compressing the optic chiasm. The intrasellar portion was heterogeneous, whereas a nodular component along the stalk demonstrated more solid, mild enhancement. The lesion measured 1.8 cm craniocaudally and 7 mm medial-laterally. The lesion presented with compression on the optic chiasm and edema in the proximal optic tracts and hypothalamus. This was a new finding compared with the MRI of the cervical spine as well as prior head computed tomography. An endoscopic transsphenoidal approach to resect the sellar and suprasellar parts of the lesion was performed. Pathology results revealed metastatic adenocarcinoma to the anterior pituitary gland with large areas of necrosis. Immunohistochemistry results revealed that the tumor cells were positive for pankeratin, keratin 7, PAX8, WT1, and estrogen receptor with null-type tumor protein p53 labeling, and negative for keratin 20, TTF1, Napsin-A, GATA3, CDX2, synaptophysin, chromogranin, p16, p63, KIT, and progesterone receptor. The final diagnosis was metastatic adenocarcinoma of Mullerian origin. Following diagnosis, a metastatic workup was done, including a whole-body positron emission tomography (PET) scan, which revealed a 5.1 cm right adnexal ovoid mass and numerous scattered liver metastases. Additionally, the PET scan revealed hypermetabolic right supraclavicular, paratracheal, celiac, and upper aortocaval nodes, consistent with metastatic disease. This report highlights high-grade serous ovarian carcinoma with pituitary metastasis as the initial presentation of systemic cancer.