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Large-cell transformation of mycosis fungoides (LCTMF) is a rare, histologically distinct phenomenon associated with an aggressive clinical course and poor overall survival. Patterns of care vary widely, with localized radiotherapy and multiagent chemotherapy as common first-line treatments. Prognosis differs significantly by extent of disease at transformation, with unifocal cutaneous involvement correlating with better outcomes compared to multifocal or extracutaneous disease. Current staging systems do not consider LCTMF as an independent entity, despite its markedly different prognosis compared to non-transformed mycosis fungoides and Sézary syndrome (MF/SS).
