Endocrine Abstracts

Pituitary metastasis is a rare complication of advanced malignancy. Tumour metastasis to a pituitary neuroendocrine tumour (PitNET) is a rarer phenomenon. We present a case of breast carcinoma with metastasis to an occult non-functioning pituitary adenoma (NFA). A 69-year-old female presented with acute bitemporal hemianopia. She had a history of breast cancer diagnosed 21 years ago (ER2 positive, HER2 negative), with disseminated sclerotic skeletal metastatic disease identified 3 years prior. Cross-sectional imaging indicated stable disease. Pituitary MRI revealed a macroadenoma with cystic degeneration, suprasellar extension, and optic chiasmal compression. Endocrine evaluation showed mild disconnection hyperprolactinaemia (656mU/l) and inappropriately low gonadotrophins for the postmenopausal state. There were no clinical features of an underlying endocrinopathy. Corticotroph and thyrotroph function was preserved. Pre-operative assessment and radiological characteristics were in keeping with an incidental non-functioning pituitary adenoma. Endoscopic transsphenoidal decompression of the sellar mass was undertaken with improvement in vision. Histopathological evaluation showed a non-functioning pituitary neuroendocrine tumour, with a Ki-67 labeling index of 5-6%. The pituitary adenoma was infiltrated by metastatic breast carcinoma, showing an estrogen receptor quick score of 8/8, a progesterone receptor quick score of 0/8, and was HER2 negative. The patient subsequently received stereotactic radiotherapy (25 Gy) to the pituitary area in five fractions. Pituitary metastases are rare and account for about 1% of all operated pituitary masses and <1% of all intracranial metastatic lesions. Pituitary metastasis can involve both the anterior and posterior lobes, but the neurohypophysis is mainly involved. This case highlights the importance of considering the possibility of metastasis to pituitary neuroendocrine tumours (PitNETs) when evaluating sellar tumours in patients with existing metastatic disease as preoperative differentiation of pituitary metastasis from NFA can be difficult. Prompt operative intervention and involvement of multidisciplinary teams can salvage vision and potentially improve cancer prognostic outcomes.