This antibody recognizes carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5, also known as CD66e) proteins (80-200kDa). CEACAM5 is synthesized during development in the fetal gut and is re-expressed in increased amounts in intestinal carcinomas and several other tumors. This MAb does not react with nonspecific cross-reacting antigen (NCA) and with human polymorphonuclear leucocytes. It shows no reaction with a variety of normal tissues and is suitable for staining of formalin/paraffin tissues. CEACAM5 is not found in benign glands, stroma, or malignant prostatic cells. Antibody to CEACAM5 is useful in detecting early foci of gastric carcinoma and in distinguishing pulmonary adenocarcinomas (60-70% are CEACAM5+) from pleural mesotheliomas (rarely or weakly CEACAM5+). Anti-CEACAM5 positivity is seen in adenocarcinomas from the lung, colon, stomach, esophagus, pancreas, gallbladder, urachus, salivary gland, ovary, and endocervix. Studies have shown that CEACAM5 could be used as a therapeutic target for adenocarcinomas of lung, colon, and stomach origin.