The FAT1 transcript, initially cloned in 1995 from a T-cell leukemia line, was predicted to encode a large type I transmembrane protein of 4588 amino acids containing thirty-four cadherin repeats, five epidermal growth factor (EGF)-like repeats, and a laminin A-G domain in its extracellular domain; in addition, FAT1 was also predicted to have a single-spanning transmembrane domain and an intracellular domain bearing homology, albeit limited, to that of classical cadherins (Figure 1A) [16]. The gene discussed is FAT1; the disease is T-cell leukemia.