IGHE and cancer: In line with these observations, it has also been speculated that a very low IgE level may be a novel early biomarker predicting cancer development, and it has been suggested that IgE-deficient patients [51] should be regularly monitored for malignancy [51,58] Any conclusion on this intriguing hypothesis is premature, and many other longitudinal studies will have to ascertain a causative link between very low or undetectable IgE levels and malignancies.