An Incidental Collision Tumor of the Sella Turcica

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To present a case describing an incidentally discovered pituitary mass that was found to be a collision tumor containing 2 distinct histologic cell types: (1) a growth hormone (GH)-secreting pituitary adenoma, and (2) a gangliocytoma. Sellar gangliocytomas are very rare benign neuroblastic tumors that originate from the posterior pituitary. The majority are associated with pituitary adenomas. The co-existence of these 2 morphologically distinct tumors is known as a collision tumor, a rare disease entity of which the pathogenesis is not well understood. We present a case of a woman with an incidentally discovered pituitary mass that was found to be a collision tumor. A 44-year-old woman presented with an incidentally discovered pituitary mass and was found to have elevated insulin-like growth factor 1 (IGF-1) levels. The patient underwent endoscopic transsphenoidal excision of the pituitary mass. Histopathology of the tumor revealed a mixed pituitary adenoma that stained for GH and prolactin, and a gangliocytoma. Postoperatively, the patient developed temporary central adrenal insufficiency and permanent diabetes insipidus. Postoperative lab studies revealed a normal IGF-1 level, and a magnetic resonance imaging scan showed no residual or recurrent tumor. While sellar gangliocytoma is a rare lesion, when it is present, a co-existing pituitary adenoma should also be suspected. Further investigation should be done to determine the pathophysiology of these collision tumors, which could be beneficial in guiding diagnosis and treatment.