Pituitary metastases are rare and often asymptomatic. They usually present with diabetes insipidus.
We present a case of a 64 year old female with a posterior pituitary metastasis and thickening of the pituitary stalk. She had a history of early oestrogen receptor positive, progesterone receptor positive, HER2 negative breast cancer diagnosed 6 years prior. She had been treated with wide local excision, four cycles of docetaxel and cyclophosphamide chemotherapy, adjuvant radiotherapy and five years of exemestane. One month prior to diagnosis of the pituitary metastasis, she had presented with bone metastases to T8, T9, T10 vertebrae, the left acetabulum and bilateral pubic rami.
Magnetic resonance imaging (MRI) demonstrated a thickened pituitary infundibulum with a possible lesion in the anterior pituitary, as well as numerous calvarial and skull base metastases. Serial MRI scans three and four months later demonstrated an increase in size of the stalk measuring 8.5 x 16 mm, with a definitive posterior pituitary lesion. There was superior displacement of the chiasm with new T2 hyperintense signal change of the right optic tract. Repeated visual field testing showed no visual field defects. Her only endocrine dysfunction was hyperprolactinaemia, likely from stalk compression, with a peak level of 1710 mIU/L and low gonadotropins (LH <0.5 IU/L, FSH 11.5 IU/L). She received dexamethasone to reduce oedema, with good effect. At no point did she develop signs or symptoms of diabetes insipidus. A pituitary biopsy confirmed metastatic carcinoma of the breast with the same morphology and hormone profile to the initial breast pathology. She received radiotherapy and is current clinically stable.
Breast cancer is the most common primary malignancy associated with pituitary metastases. The absence of typical symptoms and biochemical changes associated with diabetes insipidus does not exclude this rare, but important, diagnosis.