Immunohistochemistry (ihc) protocols and methods for diagnosing and treating cancer - claudin 18.2

An immunohistochemistry (IHC) method for determining and scoring the extent of cellular membrane expression of Claudin 18.2 in a tissue sample, comprising:

• (a) staining a tissue sample with an antibody which specifically binds to Claudin 18.2;
• (b) determining a total number of viable neoplastic or cancer cells having Claudin 18.2 cellular membrane staining, and determining a total number of staining and non-staining viable neoplastic or cancer cells in at least a portion of the tissue sample,
• wherein a neoplastic or cancer cell is counted as positively stained with anti-Claudin 18.2 antibody if there is Claudin 18.2 cellular membrane staining at any intensity above a defined threshold;
• and
• (c) determining a Claudin 18.2 score (%),
• wherein the Claudin 18.2 score (%) is the number of Claudin 18.2 staining viable neoplastic or cancer cells found in the tissue sample divided by the total number of staining and non-staining viable neoplastic or cancer cells, multiplied by 100.