Cutaneous T-cell lymphoma-associated antigen 1 (CTAGE1) is normally expressed only in testis tissue, and is found in 35% of CTCL tissues, but not in any leukemia or melanoma cell lines. The gene encoding for CTAGE1 maps to chromosome 18p11.2. CTAGE2 is a longer variant of CTAGE1 and is translated from a different open reading frame. Three other splice variants related to the major CTAGE1 and CTAGE2 variants exist, some of which are expressed only in testis, while others are expressed in a wide range of adult and fetal tissues. CTAGE1 may be an important factor in the specific immunotherapy of cutaneous T-cell lymphoma and other malignancies.