Extranodal non-Hodgkin lymphomas preferentially involve the skin. Among them, 65% are T-cell lymphomas, 25% B-cell lymphomas and about 10% rare variants or nonclassifiable lymphomas. Mycosis fungoides is the most common form of low-grade malignant peripheral cutaneous T-cell lymphoma (CTCL): Lymphomas originating from follicular center cells are the most common types of cutaneous B-cell lymphomas (CBCL). Only 15 to 25% of cutaneous lymphomas show extracutaneous manifestations at time of diagnosis. The prognosis is relatively good, since the average survival time from diagnosis is 12 to 14 years. For making the diagnosis, clinical, histo- and cytomorphological parameters often have to be supplemented by phenotypic, genotypic and molecular biologic techniques in order to establish the correct diagnosis. An important problem still is the early diagnosis and early evaluation of prognostic parameters in CTCL. The therapeutic approach is control of the disease according to stage and prognostic parameters.