T-cell malignancies presenting in the skin include mycosis fungoides, primary cutaneous anaplastic large cell lymphoma, and the related regressing lesion lymphomatoid papulosis as well as viral-associated adult T-cell leukemia/lymphoma. Rarer and more aggressive primary cutaneous lymphomas include extranodal natural killer cell/T-cell lymphoma, nasal type, subcutaneous panniculitits-like T-cell lymphoma, cutaneous gamma-delta T-cell lymphoma, and cutaneous aggressive epidermotropic CD8+ cytotoxic T-cell lymphoma. Systemic T-cell lymphomas that frequently involve the skin secondarily, such as angioimmunoblastic T-cell lymphoma, systemic anaplastic large cell lymphoma, and peripheral T-cell lymphoma, unspecified, are covered in Chap. 22.