Neuroendocrine tumor of unknown origin metastasizing to a growth hormone-secreting pituitary adenoma.

Abstract

Metastasis of a neuroendocrine tumor to the anterior pituitary is extremely rare. A 55-year-old woman presented with features suggestive of acromegaly and bone and joint pain. A bone scan suggested metastatic disease. A biopsy of the lumbar spinal lesions revealed a neuroendocrine tumor. Magnetic resonance imaging of the sella demonstrated a lesion with parasellar and suprasellar extensions. Given the need for tissue diagnosis and optic compression, the sellar lesion was removed via transsphenoidal hypophysectomy. Histology of the biopsy indicated two different tumors in close association. One showed histological features of a pituitary adenoma, whereas the other was a neuroendocrine carcinoma. The pituitary adenoma was immunopositive for growth hormone (GH), whereas the neuroendocrine carcinoma was immunopositive for serotonin and bombesin and immunonegative for GH. This is the first report of a serotonin and bombesin immunopositive neuroendocrine tumor of unknown primary origin metastatic to a GH-secreting pituitary adenoma, resulting in acromegaly.