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Primary cutaneous lymphomas are extranodal non‐Hodgkin lymphomas and consist of different variants defined by specific clinicopathological and immunophenotypic features. Primary cutaneous T‐cell lymphomas are the most common subset and are derived from resident memory T cells, whereas primary cutaneous B‐cell lymphomas are more closely related to their nodal counterparts with derivation from B cells at different stages of differentiation. Whilst the underlying pathogenesis of cutaneous lymphomas remains unclear, there is emerging evidence for a heterogenous pattern of somatic mutations and epigenetic events. Although the prognosis for many indolent primary cutaneous lymphoma variants remains excellent, the treatment of some rare variants and advanced stages of mycosis fungoides and Sezary syndrome represents an unmet medical need in view of high levels of chemotherapy resistance and limited durable responses. A variety of novel biological agents have been recently approved but long‐term remissions are rare. There is still an urgent need to clarify the underlying molecular pathogenesis and identify more effective targeted therapies for mycosis fungoides and Sézary syndrome.
Keywords primary cutaneous lymphomas, secondary cutaneous lymphomas, mycosis fungoides, Sézary syndrome