P40

P40 is an immunohistochemistry marker used primarily to identify squamous cell carcinoma, especially in lung biopsies. It helps differentiate between squamous and non-squamous histological types.

It is used during tissue biopsy evaluations of tumors, particularly in the lungs, head, neck, and esophagus, where squamous cell carcinoma is suspected.

The pathologist applies specific antibodies to formalin-fixed, paraffin-embedded tissue sections to visualize P40 protein expression.

Positive nuclear staining for P40 supports squamous differentiation. Negative staining suggests an alternate tumor origin.

Identifying tumor subtype aids in prognosis and selecting appropriate therapies, such as chemotherapy or targeted therapies.