Overview of cutaneous malignant lymphoma Cutaneous malignant lymphoma is a malignant lymphoma with skin damage as the initial or prominent manifestation and can be primary or secondary to lymph nodes and other organs. Primary cutaneous malignant lymphoma is an extra-nodal lymphoma that first develops in the skin and has no evidence of extra-skin tissue or organ invasion at the time of diagnosis. PCML can be either a cutaneous T-cell lymphoma or a cutaneous B-cell lymphoma. Rather, PCML is a heterogeneous and complex group of diseases with widely varying clinical presentation, histologic type, immunophenotype, and prognosis. Secondary cutaneous malignant lymphoma is part of the manifestation of systemic malignant lymphoma, and PCML differs from secondary cutaneous malignant lymphoma or intra-nodal lymphoma in terms of clinical presentation, immunophenotype, tumor biological behavior, and prognosis. Therefore, when diagnosing cutaneous malignant lymphoma, it must first be clarified whether it is primary or secondary. Non-Hodgkin’s lymphoma is the most common form of cutaneous lymphoma, while cutaneous Hodgkin’s lymphoma is very rare. Therefore, the term PCML usually refers to cutaneous non-Hodgkin’s lymphoma. Gastrointestinal NHL is the most common type of extra nodal lymphoma, followed by cutaneous NHL. According to the Dutch and Austrian Skin Lymphoma Collaborative Group of 1905 cases, CTCL accounted for 76% and CBCL for 24%. The most common type is mycosis fungoides and its variants. Other more common types include mesenchymal large cell lymphoma of the primary skin, lymphomatoid papulosis, follicle-centric lymphoma of the primary skin, and marginal zone B-cell lymphoma of the primary skin. Other rare types include Sézé’s syndrome, diffuse large B-cell lymphoma/leg type with primary skin, NK/T lymphoma/nasal type with primary skin, and many others.