Primary cutaneous lymphomas are extranodal non-Hodgkin lymphomas. They are classified into the two main groups of primary cutaneous T- and B-cell lymphomas. Very rare cases are derived from NK or plasmacytoid dendritic cells. The annual incidence is 1/100,000. Two-thirds of the patients have primary cutaneous T-cell lymphoma, and the remaining one-third have primary cutaneous B-cell lymphoma. Over the years, tremendous progress has been made regarding the diagnostics and classification of cutaneous lymphomas. An exact classification of cutaneous lymphomas is of great importance for the patient, because the different skin lymphomas have very different prognoses and require different therapeutic regimens.
The basis for making a diagnosis is a clinical-pathological correlation, including the use of several immunohistochemical markers and molecular biological methods. Treatment of cutaneous lymphoma is adapted to the type of lymphoma and disease stage. First-line therapy consists of treatments that target the skin. Systemic treatment is used in advanced disease. Many targeted therapies have been introduced into routine clinical care in recent years. This review presents an up-to-date approach to the diagnosis and treatment of primary cutaneous lymphomas.