The paper presents the current state of research on the 140-kD isoform of neural cell adhesion molecule CD56/NCAM. Briefly discussed biosynthesis, structure, and the putative function of the molecule. Different forms of the molecule results not only from changes posttranscriptional mRNA, but also during the post-translational modifications involving the attachment of various groups chemicznych.Wskazano major site of its occurrence in both normal tissues, as in human pathology, mainly in malignant tumors. In relation to normal tissues except the nervous system important positions of CD56 appear to be endocrine glands, among malignant tumors in addition to tumors of neuroectodermal origin CD56 is present on cells of many hematological malignancies, sarcomas, rhabdomyosarcoma, and some cancers. It also highlighted the possibility of using CD56 signs in clinical medicine.