Ki-1–positive ALCL is a recently recognized entity.5 First described in 1982, the Ki-1 antibody was believed to be specific for Reed-Sternberg cells of Hodgkin lymphoma; however, it has subsequently been shown to identify a variety of benign and malignant conditions including LyP and Ki-1–positive ALCL.4 Ki-1–positive ALCL is considered to be high grade in the updated Kiel classification for lymphoma.6 - 7 It can be of B-, T-, or null-cell lineage, with the T-cell phenotype being the most common.4 Disease is usually localized to lymph nodes; sites of extranodal disease include the skin, lung, gastrointestinal tract, soft tissue, cerebrospinal fluid, and bone. In the skin, the disease may arise either de novo (primary cutaneous Ki-1–positive ALCL) or from a preexisting lymphoma or benign condition of the skin, such as dermatitis (secondary cutaneous Ki-1–positive ALCL).8 The Ki-1–positive neoplastic cells are pleomorphic, contain abundant cytoplasm, and show large, indented nuclei with prominent nucleoli. Mitotic figures can be numerous.9