Mycosis fungoides and Sézary syndrome (SS) are primary cutaneous T-cell lymphomas [1-4]. 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 . Although the pathogenic role of HTLV-I has been entertained, a large multinational study has ruled out the involvement of this retrovirus in mycosis fungoides and SS.
Mycosis fungoides affects mainly older adults. 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. Transformation to a large T-cell lymphoma can occur.
Sézary syndrome is a disease of the elderly, characterized by erythroderma and circulating Sézary cells with characteristic cerebriform nuclei.
Haematological and pathological features
The peripheral blood is usually normal in mycosis fungoides but circulating lymphoma cells may be present in later stages. Skin biopsy (Figures 17.1,17.2,17.3) shows epidermotropism in the early stages with formation of intraepidermal Pautrier's microabscess in some but not all cases .
Skin biopsy in mycosis fungoides. H&E, x 4 objective.
Skin biopsy in mycosis fungoides; at higher power the infiltration of lymphocytes into the epidermis is apparent. H&E, x 40 objective.
Skin biopsy in mycosis fungoides; several Pautrier's microabscesses are apparent. H&E, x 60 objective.
By definition, circulating Sézary cells (Figures 17.4,17.5,17.6) are required for the diagnosis of SS. Suggested minimum diagnostic criteria of the International Society for Cutaneous Lymphomas are one of the following: an absolute Sézary cell count of at least 1 × 109/l, relevant immunophenotypic abnormalities (see below) or demonstration of a T-cell clone by molecular or cytogenetic studies . Sézary cells may be either small or large. Individual patients may have mainly small cells, mainly large cells or a mixture of both. Transformation from small cell disease to large cell disease can occur . Sézary cells are characterized by a deeply convoluted or cerebriform nucleus. In small cells the cytoplasm is scanty and the nucleus appears to have a grooved surface. Larger cells have more cytoplasm and nuclei may appear cerebriform or lobulated. In both variants, nuclei may be hyperchromatic and cytoplasmic vacuoles may encircle the nucleus (see Figures 17.5 and 17.6). The characteristic nuclear form is most ...