The occurrence of a cancer that follows a previously treated malignant
neoplasm but is not considered a metastasis of the initial neoplasm. This
second malignancy may have the same or different histological type and can
occur in the same or different organs as the previous neoplasm but in all
cases arises from an independent oncogenic event. The development of the
second neoplasm may or may not be related to the treatment for the previous
neoplasm since genetic risk or predisposing factors may actually be the cause.