Research found that left side of human body is more likely to be the one on which malignant tumors occur. Reason for that is still not discovered but reports show that 10% of invasive tumors appear more on the left leg, arm and side of the body then on the right one.

Study showed that age group or sex had nothing to do with this results and researchers dismissed possibility that more tumors occur on the left side as a result of exposure of left arm to sun during the drive or maybe because of uneven application of sun block lotions. Also, they claim that occurrences of tumors is not a result of uneven distribution of melanocytes which is a pigment that protects body from UV light.

More research needs to be done in order to explain why is left side of the body more likely to be affected by tumors than the right one. Lung cancer is specific example because it seems that it favors left side over the right one.