A Rare Case of Recurrent Pituitary Collision Tumors.

Pituitary collision tumors are sporadically reported and rare. We present a case of pituitary collision tumors with nonfunctioning pituitary adenoma (NFPA) and craniopharyngioma. In order to look for any common activated pathway, we examined WNT/β-CATENIN signaling activation, known to be involved in tumorigenesis in both craniopharyngioma and NFPA. We found nuclear accumulation of β-CATENIN protein and expression of LEF1 protein, markers of active β-CATENIN signaling in the craniopharyngioma but not in the pituitary adenomas. In our case, the NFPA is invasive macroadenoma, which is a frequently identified type of pituitary adenoma in collision tumor cases. Recurrence of this tumor was first observed after 8 years of follow-up. Based on this case, we suggest that pituitary collision tumors require long-term follow-up.