The present invention belongs to the field of oncology. The invention relates to antibodies with specified sequence which are specific for an epitope which is coded by the variant exon v6 of the CD44 gene and to derivatives of said antibody. The invention also provides nucleic acid molecules encoding said antibody proteins. The invention furthermore pertains to methods for producing said antibody proteins. The invention also provides pharmaceutical compositions comprising said antibody proteins. The invention furthermore is concerned with the use in the manufacture of a medicament for the treatment of cancer.