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Cutaneous lymphomas are a group of disorders characterized by the localization of malignant lymphocytes (tropism) to the skin. Lymphomas presenting in the skin may be due to primary or secondary involvement. In clinical practice, primary cutaneous lymphomas are more common and often seen by dermatologists at presentation, while lymphomas due to secondary involvement represent metastatic disease from a primary nodal or systemic lymphoma, and are associated with a worse prognosis. Primary cutaneous lymphomas, by definition, are cutaneous lymphomas with no extracutaneous manifestations of the disease at presentation.
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Within the group of primary cutaneous lymphomas, T-cell lymphomas are more common, comprising approximately two-thirds of cases, in contrast to nodal lymphomas where B-cell lymphomas predominate over T-cell lymphomas.
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Mycosis fungoides (MF) represents the most common type of cutaneous lymphoma and is a malignancy of CD4+ skin homing, helper T-cells (Figures 12–1, 12–2, 12–3, 12–4, 12–5, 12–6, 12–7, 12–8, 12–9, 12–10, 12–11, 12–12, 12–13, 12–14, 12–15, 12–16, 12–17, 12–18, 12–19, 12–20, 12–21, 12–22, 12–23, 12–24, 12–25, 12–26, 12–27, 12–28). It has an indolent behavior, in which patients present with patches in the early stages, with the sequential development of plaques and tumors over time. However, many patients remain well for many decades, with patch and plaque stage disease and only in about 10% of cases do patients develop progressive disease to tumor stage or extracutaneous involvement.
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