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

Abstract

Background: Metastasis of a neuroendocrine tumor to the anterior pituitary is extremely rare.

Methods: 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.

Results: 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.

Conclusions: 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.