PITUITARY GLAND METASTASIS OF BREAST CANCER PRESENTING AS DIABETES INSIPIDUS

Abstract

INTRODUCTION/BACKGROUND
Metastasis to the pituitary gland is extremely rare and represents only 1% of pituitary tumours. The most frequently reported malignancies that metastasize to the pituitary gland are lung, renal and breast cancers.

CASE
A 49-year-old female with advanced left breast carcinoma with bone metastasis presented with a week’s history of worsening back pain and bilateral lower limb weakness. On examination, vital signs were stable and neurological examination showed bilateral lower limb motor neuron lesions with muscle strength of 3/5 and loss of sensation up to T4. During admission, she developed polyuria with hypernatremia. Laboratory examinations showed sodium of 150 mmol/L (NR: 136-145), serum osmolality of 318 mOsm/ kg (NR: 275-295), urine osmolality of 142 mOsm/kg (NR: 275-295). Renal function, serum calcium, potassium and glucose were all normal. Anterior pituitary hormone panel showed panhypopituitarism with TSH: 0.24 m IU/L (NR: 0.27-4.2), FT4: 11.7 pmol/L (NR: 12-22), FSH: 7.35 IU/L (NR: 25.8-134) and LH: 5.92 IU/L (NR: 7.7-58.3). FSH and LH were low despite the patient being post-menopausal. The cortisol axis was not assessed as the patient was on dexamethasone. Cranial and pituitary MRI revealed parietal and occipital skull lesions, small right temporal and frontal brain lesions, and thickened pituitary stalk measuring 0.5 cm with a nonenhancing posterior pituitary lesion suggestive of metastasis. Central diabetes insipidus occurs in less than 1% of patients with primary pituitary adenoma, while it is the presenting symptom in 70–80% of patients with pituitary metastasis. The radiological diagnosis is based on MRI which can highlight an iso-intense or hypo-intense mass on T1-weighted images with a high-intensity signal on T2-weighted images, a homogeneous enhancement with gadolinium and loss of the high signal pituitary signal intensity on T1-weighted images.

CONCLUSION
The prognosis for metastases to the pituitary gland is poor due to the presence of advanced neoplastic disease. Posterior pituitary lesions are rare, therefore being a red flag for metastasis.