TTF-1 (Thyroid Transcription Factor-1), also known as NKX2.1, is a nuclear transcription factor essential for the development and function of the thyroid gland, lung, and ventral forebrain. It is frequently used as an immunohistochemical marker in neuropathology and oncopathology.

TTF-1 plays a key role in regulating genes involved in:

• Thyroid development and hormone production
• Lung morphogenesis and surfactant protein expression
• Brain development, particularly in the hypothalamus and pituitary gland

In pathology, TTF-1 is commonly used as a marker of origin for tumors, especially in the following contexts:

• lung adenocarcinoma: Strongly positive
• thyroid carcinoma: Positive in most types
• posterior pituitary tumor: Universally positive across subtypes, including:
  • pituicytoma
  • granular cell tumor
  • spindle cell oncocytoma

In PPTs, diffuse nuclear positivity for TTF-1 helps distinguish them from other sellar masses such as pituitary adenomas or craniopharyngiomas.

• immunohistochemistry
• pituitary gland
• posterior pituitary tumor
• S100 protein
• vimentin
• Ki67