The present invention provides the amino acid and nucleic acid sequences of heavy chain and light chain complementarity determining regions of a cancer specific antibody. In addition, the invention provides cancer specific antibodies and immunoconjugates comprising the cancer specific antibody attached to a toxin or label, and methods and uses thereof. The invention also relates to diagnostic methods and kits using the cancer specific antibodies of the invention. Further, the invention provides a novel cancer-associated antigen and its uses thereof.