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Mycosis fungoides and Sézary syndrome (SS) are primary cutaneous T-cell lymphomas [1–5]. Mycosis fungoides is characterized by cutaneous disease without circulating lymphoma cells necessarily being present whereas the diagnosis of SS requires the presence of circulating neoplastic cells. In the World Health Organization/European Organization for Research and Treatment of Cancer (WHO-EORTC) classification, these are two distinct types of primary cutaneous T-cell lymphoma [1]. Although the pathogenic role of HTLV-1 has been entertained, a large multinational study has ruled out the involvement of this retrovirus in mycosis fungoides and SS [6]. Features of other primary cutaneous T-cell lymphomas included in the revised WHO classification will be also briefly outlined in this chapter.

Clinical features

Mycosis fungoides affects mainly older adults with a male predominance. It is a slowly progressive condition characterized by cutaneous patches, plaques and, finally, tumours as a result of infiltration of the skin by lymphoma cells with cerebriform nuclei. Visceral dissemination and/or blood involvement can occur at late stages of the disease.

SS is a disease of the elderly, characterized by erythroderma and circulating Sézary cells with characteristic cerebriform nuclei. Patients often manifest pruritus; visceral involvement is variable.

Staging of mycosis fungoides and SS is based on the guidelines of the International Society for Cutaneous Lymphomas and the EORTC [1]. These consider extent of skin involvement, nodal disease, visceral disease and blood involvement.

Haematological and pathological features

The peripheral blood is usually normal but in mycosis fungoides circulating lymphoma cells may be present in later stages. Skin biopsy (Figures 18.1,18.2,18.3) shows epidermotropism in the early stages with formation of intraepidermal Pautrier’s microabscesses in some but not all cases. In the tumoural stage, the dermal infiltrates are more prominent and the epidermotropism may be lost. At this stage, histological transformation defined by the presence of greater than 25% large lymphoid cells, can occur. Three variants of mycosis fungoides – folliculotropic, pagetoid reticulosis and granulomatous slack skin type – are recognized by the WHO [3].

Figure 18.1

Skin biopsy in mycosis fungoides. Haematoxylin and eosin stain (H&E), ×4 objective.

Figure 18.2

Skin biopsy in mycosis fungoides; at higher power the infiltration of lymphocytes into the epidermis is apparent. H&E stain, ×40 objective.

Figure 18.3

Skin biopsy in mycosis fungoides; several Pautrier’s microabscesses are apparent. H&E stain, ×60 objective.

By definition, circulating Sézary cells (Figures 18.4, 18.5, 18.6) are required for the diagnosis of SS. Suggested minimum diagnostic criteria of the International Society for Cutaneous Lymphomas are one ...

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