Clusterin expression is common in systemic and cutaneous anaplastic large cell lymphoma (ALCL). Mycosis fungoides (MF) in large cell transformation can resemble ALCL. In this study, we immunohistochemically assessed for clusterin in 97 skin biopsy specimens, including 70 MF cases and 27 other cutaneous neoplasms including ALCL, peripheral T-cell lymphoma unspecified (PTCL), and lymphomatoid papulosis (LyP). Clusterin was positive in 36 (51%) of 70 cases of MF and correlated with clinical stage in 68 cases: 3 of 21 stage I, 11 of 20 stage II, and 23 of 27 stage III/IV. Clusterin expression also correlated with type of skin lesion (3/19 patch, 13/28 plaque, and 20/23 tumor/erythroderma) and number of large cells (6/30 small cell, 12/18 with increased large cells, and 18/22 with large cell transformation). Clusterin expression was not specific for MF as it also was positive in 3 of 3 cases of LyP, 2 of 2 systemic ALCL cases involving skin, 7 of 16 cutaneous ALCLs, and 1 of 6 PTCLs.