CEACAM5 and cancer: Carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), carbohydrate antigen 125 (CA-125), and other serum markers are often characterized by low specificity and sensitivity and their expression can be affected by non-pathological conditions: both these factors make these indicators not ideal as a primary choice for cancer diagnosis and prognosis, highlighting the need for novel, valid tumor biosignatures [139].