Colorectal cancer manifesting with metastasis to prolactinoma: report of a case involving symptoms mimicking pituitary apoplexy.

Pituitary metastasis is an uncommon first presentation of systemic malignancy. The most common presenting symptom of pituitary metastasis is diabetes insipidus reflecting involvement of the stalk and/or posterior pituitary. We herein present a unique case of the coexistence of both a functioning pituitary adenoma (prolactinoma) and pituitary metastasis of advanced colorectal cancer with pituitary apoplexy as the first manifestation of underlying malignancy. The present case emphasizes the need to consider pituitary metastasis as a differential diagnosis in patients presenting with pituitary lesions and be aware that tumor-to-tumor metastasis can occur unexpectedly in those with pituitary metastases.