Napsin A

What is the Napsin A test used for?

 Napsin A is an immunohistochemical (IHC) stain used primarily to identify lung adenocarcinomas and distinguish them from other types of lung cancer and metastases. Napsin A is an aspartic proteinase involved in surfactant protein B processing and is highly expressed in type II pneumocytes.


When is this test recommended?

This test is typically used when a pathologist is examining lung tissue samples and needs to determine the type of lung cancer present. It is especially useful in confirming a diagnosis of primary lung adenocarcinoma and differentiating it from squamous cell carcinoma or metastases from extrapulmonary tumors.


How is the test performed?

The test is carried out on a paraffin-embedded tissue sample using immunohistochemistry. A Napsin A-specific antibody is applied to the tissue, and if the protein is present, it will stain the tumor cells. The pattern and intensity of staining help determine the diagnosis.


What does a positive Napsin A result indicate?

A positive Napsin A result supports a diagnosis of lung adenocarcinoma. It is often used in conjunction with other markers, such as TTF-1, to confirm the diagnosis. The absence of Napsin A may suggest a different histological subtype or a non-pulmonary origin of the tumor.


Are there other cancers where Napsin A is expressed?

While Napsin A is most commonly associated with lung adenocarcinomas, it may also be expressed in some renal cell carcinomas. However, its expression in other cancers is typically low, making it a relatively specific marker for lung adenocarcinoma in the appropriate clinical context.