Neuroradiology

Choristoma

(also called granular cell tumour and myoblastoma), an extremely rare primitive neoplasm of the neurohypophysis composed of large polygonal cells with small nuclei and granular cytoplasm. Microscopic nests of these cells in the neurohypophysis are a fairly frequent finding at postmortem. Since these lesions can be extremely vascular, preoperative diagnosis is important in surgical planning. Choristoma is usually posteriorly situated within the gland and obscures the normal posterior lobe hyperintensity. However, no typical signal pattern has been described on tomographic CT and MR imaging and a presumptive diagnosis on the basis of location is difficult as adenoma is still, by far, the most frequent posterior hypophysis mass.

FS