5′-nucleotidase (5′-NT), also known as ecto-5′-nucleotidase or CD73 (cluster of differentiation 73), is an enzyme that in humans is encoded by the NT5E gene. CD73 commonly serves to convert AMP to adenosine. A deficiency of NT5 occurs in a variety of immunodeficiency diseases. Rare allelic variants are associated with a syndrome of adult-onset calcification of joints and arteries (CALJA) affecting the iliac, femoral, and tibial arteries reducing circulation in the legs and the joints of the hands and feet causing pain. Due to enzymatic and non-enzymatic properties, CD73 is involved in cancer-related processes and is upregulated in many cancers such as leukemia, glioblastoma, melanoma, oesophageal, prostate, ovarian and breast cancer. It is an important key molecule in cancer regulation and development and is involved in tumor progression.