It is generally believed that the expression of a gene iS restricted "within the right place and at the right time".This principle has long been considered applicable as well to the expression of immunoglobulin(Ig)lymphocytes of B cell lineage.However,increasing evidence has shown Ig "paradoxically" expressed in malignant tumors of epitheliaI origin.We reviewed the recent progress in the study of cancer-derived Ig,and also discussed its mechanisms and possible functions,trying to arouse interest and attention to those working in the field of immunology and oncology.