RESUMO
Null cell adenoma is composed of adenohypophyseal cells that show no evidence of any specific cell type differentiation by immunohistochemistry or transcription factors like pituitary-specific positive transcription factor 1 and steroidogenic factor 1. Though rare, pituitary ependymoma and germinoma are also known to occur at sellar region and in such instances, it is challenging to differentiate them from a pituitary null cell adenoma featuring papillary architecture and perivascular pseudo-rosettes. We describe a case of an elderly diabetic lady presenting with headache and blurring of vision for past 3 months due to a sellar tumour. The histology was diagnostically challenging with notable presence of numerous perivascular pseudo-rosettes and negative immunoreactivity for all pituitary hormones. The differential diagnosis and importance of ancillary techniques is discussed.