It has been shown that, at least in some malignancies, tumour associated antigens are expressed in tumour tissues but the levels of the tumour associated antigens are not elevated in the serum [45], suggesting that the levels of circulating MSLN do not reflect the amount of MSLN at the tumour site where antigen presenting cells and infiltrating effector T cells can be exposed to MSLN. The gene discussed is MSLN; the disease is neoplasm.