Various diseases should be considered when evaluating a suprasellar mass. Diabetes insipidus has been reported as the primary manifestation in a patient with Langerhans cell histiocytosis involving the hypothalamopituitary axis (HPA) and can be helpful for the diagnosis. The use of endoscopic biopsy for suprasellar masses has increased. However, as it is difficult to make a diagnosis with endoscopic biopsy because of the many artifacts, pathologists must be careful. Langerhans cell histiocytosis involving the HPA as solitary lesions is rare. We report the eighth case that provides neurologists, radiologists, and pathologists with various implications.