[Diabetes insipidus disclosing metastasis of breast adenocarcinoma]

We are reporting on a case of diabetes insipidus (DI) and anterior pituitary failure revealing a breast cancer metastasis. Ten years after being diagnosed with a unilateral breast cancer, the patient presented with asthenia, thirst, polyuria and nocturia improved by subcutaneous DDAVP. MRI revealed a thickened pituitary stalk. DI is uncommon, late and usually asymptomatic in breast cancer. The association with an anterior pituitary failure is even more rare. In our patient the metastasis is in the pituitary stalk and seems to be due to meningeal deposits. MRI appears to be the best procedure to perform, showing a thickening stalk. Extension to the pituitary gland is related to direct tumor invasion from adjacent structures rather than haematogenous spread.