CA50 (carbohydrate antigen 50) is an antigen isolated from the monoclonal antibody Colo-50 of colon cancer and rectal cancer cell line COLO.
        CA50 is generally not present in normal tissues, but it can be detected in nearly 5% of Lewis-negative people.
        The serum CA50 concentration of normal people is less than 25 IU/mL.

CA50 vs. CA199, difference and connection
        Structure: CA50 and CA199 have cross antigenicity. The epitope of CA50 recognized by the monoclonal antibody is a carbohydrate structure, including sialic acid-N-tetraoxyceramide and sialylated Lewis blood group antigen.
        CA50 has the same antigenic determinants as CA199, but CA50 has a unique sialylated Lewis antigen-this antigen lacks fucose residues (highlighted).
        Function: Serum CA50 test is often recommended for prognosis prediction and postoperative monitoring, especially in patients with gastrointestinal cancer with normal serum CA199 levels.

What is the significance of CA50 in malignant diseases
        Elevated serum CA50 levels are usually used clinically to diagnose or monitor pancreatic cancer and colorectal cancer. Because CA50 is widely present in pancreas, gallbladder, liver, stomach, colorectal, bladder, and uterus, its tumor recognition spectrum is broader than CA19-9.
        When the cell becomes malignant, certain invertases that can only be active in the embryonic stage are activated due to the inactivation of glycosyl invertase, resulting in changes in the structure and properties of carbohydrates on the cell surface to form CA50. Therefore, it is a universal tumor marker-related antigen, rather than a tumor marker that specifically refers to a certain organ.

The role of CA50 in disease diagnosis
        CA50 and pancreatic cancer
        The increase in serum CA50 level is very effective in the diagnosis of pancreatic cancer, and its sensitivity exceeds 84%. Although CA50 is also expressed in normal pancreatic tissues, elevated CA50 is mainly seen in patients with pancreatitis and pancreatic cancer.
        In clinical practice, it is often used in combination with CA199, CA242 and CEA for the diagnosis and prognosis of pancreatic cancer.
        Note: CA50, like CA199, is prone to false negative results in Lewis-negative pancreatic cancer patients. The detection rates of CA50 and CA199 in Lewis-negative pancreatic cancer patients were only 12.8% and 19.1%, respectively.
        Because CA125 and CEA have epitopes unrelated to Lewis structure, they can replace CA50 and CA199 as tumor markers for the diagnosis of Lewis-negative pancreatic cancer.
         CA50 and lung cancer
        CA50 expression is found in 65%-68% of small cell lung cancer and non-small cell lung cancer tissues, and the serum CA50 level has good diagnostic value for both small cell lung cancer and non-small cell lung cancer.
        CA50 and precancerous lesions
        Atrophic gastritis is a kind of precancerous lesions. The concentration of CA50 in gastric juice of atrophic gastritis patients has significantly changed compared with that of normal people. Therefore, CA50 can be considered as one of the indicators of precancerous diagnosis.

The role of CA50 in the differentiation of benign and malignant diseases
        Serum CA50 levels above 20 IU/mL were detected in 6% of tuberculous pleural effusions and 78% of malignant pleural effusions. The CA50 levels in malignant pleural effusions were significantly higher than those in benign pleural effusions. Therefore, the detection of CA50 may also have a greater clinical diagnostic value for differentiating benign and malignant pleural effusions.
        The expression of CA50 in malignant pancreatic tissue is higher than that in benign pancreatic tissue. As a serum tumor marker, CA50 can distinguish pancreatic cancer from chronic pancreatitis with a sensitivity of 46% and a specificity of 91%.
        When pancreatitis, colitis, and pneumonia occur, CA50 will increase, but as inflammation is eliminated, its value will also decrease.