Cutaneous T-cell lymphomas-An update 2021.

Cutaneous T-cell lymphomas (CTCL) represent the majority of primary cutaneous lymphomas (CL). Mycosis fungoides (MF) and cutaneous CD30+ lymphoproliferative disorders account for 80% of all CTCL. CTCL show overlapping histological features. Thus clinical-pathological correlation is of importance to achieve final diagnosis. MF shows a characteristic evolution with patches, plaques, and in a subset of patients (10%-20%) with tumors. Therapy is stage-adapted with skin-directed therapies such as UV-light therapies and corticosteroids in early disease stage (i.e., patch and limited plaque stage) and systemic therapies (retinoids, interferon, mono chemotherapy, targeted therapy) and/or radiation therapy (local or total skin beam electron) in advanced stages. Novel therapies include targeted therapy such as mogamulizumab (anti-CCR4) or brentuximab vedotin (anti-CD30) and histone deacetylase inhibitors. Considering the impact of targeted therapies, biomarkers such as CD30 are not only crucial for the diagnosis and correct classification of an individual lymphoma case, but also for therapy as they may represent therapeutic targets. In the recently revised WHO classification 2017 and the updated WHO-EORTC classification for CL 2018, primary cutaneous CD8+ acral T-cell lymphoma has been introduced as a new still provisional entity. It displays characteristic clinical, histological, and phenotypic features and exhibits an excellent prognosis. Rare, but aggressive CTCL include cutaneous primary cutaneous aggressive epidermotropic CD8-positive T-cell lymphoma and cutaneous gamma/delta T-cell lymphoma, which present with rapid onset of necrotic or ulcerated plaques and tumors. As they have a poor prognosis, treatment includes multiagent chemotherapy and hematopoietic stem cell transplantation.