Do abnormal chromosomes cause cancer?

Sometimes. Many cancers seem to have a genetic component. For example, those who have Down syndrome (an extra chromosome #21) are more likely to get leukemia than those who do not have abnormal chromosomes. However, many of the minor chromosome changes are not associated with an increased risk of getting cancer. It all depends on the chromosome problem itself.
Yes. Chromosomal abnormalities are responsible for many cancers, includind lung, breast, and several leukemias and lymphomas.
Yes. But all. Chromosomal abnormalities are not equal. Some during development are lethal and cause of sponaneous abortion (fetal demise), others cause developmental sydromes, trisomy 21 and down syndrome; trisomy 18 and edwards syndrome. The bcr-abl translocation causes cml. Many cancers have losses or gains of unkown significance.