TTF-1-Expressing Supratentorial Embryonal Tumors (PNET): A Clinicopathologic Study of Two Cases and Literature Review of TTF-1-Positive Primary Brain Tumors

Abstract

Thyroid transcription factor 1 (TTF-1) is a nuclear polypeptide, tissue-restricted member of the homeobox protein family, that when attached to DNA plays a crucial role in regulating the expression of select genes during early embryonic development of the thyroid, lung, and brain. As often happens, the initial enthusiasm for the diagnostic value of TTF-1 as a selective immunohistochemical marker of lung and thyroid tumors began to dwindle, its wider use led its demonstration in tumors arising from other organs. TTF-1 expressing primary brain tumors arising in the 3rd ventricle were first reported in 2004. More recently, tumors arising from the posterior hypophysis (pituicytoma, granular cell tumor of the sellar region, and spindle cell oncocytoma of the pituitary gland) as well as chordoid glioma of the third ventricle and subependymal giant cell astrocytoma have been proven to be TTF-1 immunoreactive. We present for the first time the expression of TTF-1 in two primary embryonal tumors (PNET) of the anterior basal brain. One was in a 6½-year-old female and the other in a 36-year-old female. General surgical pathologists and neuropathologists should be aware of the potential TTF-1 expression in tumors of the ventral forebrain.