Abstract: An in vitro diagnostic method for detecting the presence in a patient of cancer cells or other cells producing mucin antigens comprises the step of testing a sample of a physiological fluid, particularly a sample of blood, blood serum or blood plasma, taken from the patient to detect the presence of small intestine mucin antigen (SIMA) and/or large intestine mucin antigen (LIMA) in the sample. An in vitro diagnostic kit is also disclosed.