===== TTF-1 =====

**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.

==== Function ====

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**


==== Diagnostic Utility ====

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]].

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==== Interpretation in Immunohistochemistry ====

| Marker           | Expression in PPTs      |
|------------------|--------------------------|
| **TTF-1**         | ✅ Strong nuclear positivity |
| **Vimentin**      | ✅ Positive                |
| **S100 protein**  | ✅ Often positive          |
| **Cytokeratin**   | ❌ Negative                |
| **Chromogranin A**| ❌ Negative                |

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==== Related Terms ====

  * [[immunohistochemistry]]
  * [[pituitary gland]]
  * [[posterior pituitary tumor]]
  * [[S100 protein]]
  * [[vimentin]]
  * [[Ki67]]