General Information About Mycosis Fungoides and the Sézary Syndrome
Mycosis fungoides and the Sézary syndrome (MF/SS) are neoplasias of malignant T lymphocytes that usually possess the helper/inducer cell surface phenotype. These kinds of neoplasms initially present as skin involvement and as such have been classified as cutaneous T-cell lymphomas. These types of lymphomas are included in the Revised European-American Lymphoma classification as low-grade T-cell lymphomas, which should be distinguished from other T-cell lymphomas that involve the skin, such as anaplastic large cell lymphoma (CD30 positive), peripheral T-cell lymphoma (CD30 negative, with no epidermal involvement), adult T-cell leukemia/lymphoma (usually with systemic involvement), or subcutaneous panniculitic T-cell lymphoma.[2,3] These histologic types of T-cell lymphomas are discussed in another PDQ summary. (Refer to the PDQ summary on Adult Non-Hodgkin Lymphoma Treatment for more information.) In addition, a number of benign or very indolent conditions can be confused with mycosis fungoides. Consultation with a pathologist who has expertise in distinguishing these conditions is important.
The prognosis of patients with MF/SS is based on the extent of disease at presentation (stage). The presence of lymphadenopathy and involvement of peripheral blood and viscera increase in likelihood with worsening cutaneous involvement and define poor prognostic groups. The median survival following diagnosis varies according to stage. Patients with stage IA disease have a median survival of 20 or more years. The majority of deaths for this group are not caused by, nor are they related to, MF. In contrast, more than 50% of patients with stage III through stage IV disease die of MF, with a median survival of less than 5 years.[5-7] A report on 1,798 patients from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program (SEER) database found an increase in second malignancies (standardized incidence ratio of 1.32; 95% confidence interval, 1.15–1.52), especially for Hodgkin and non-Hodgkin lymphoma and for myeloma.
Typically, the natural history of MF is indolent. Symptoms of the disease may present for long periods, an average of 2 to 10 years, as waxing and waning cutaneous eruptions prior to biopsy confirmation. MF/SS is treatable with available topical and/or systemic therapies. Curative modalities, however, have thus far proven elusive, with the possible exception of patients with minimal disease confined to the skin.
Cutaneous disease typically progresses from an eczematous patch/plaque stage covering less than 10% of the body surface (T1) to plaque stage covering 10% or more of the body surface (T2), and finally to tumors (T3) that frequently undergo necrotic ulceration.[4,10] SS presents with generalized erythroderma (T4) and peripheral blood involvement. However, there is some disagreement about whether the MF and SS are actually variants of the same disease. There is consensus that patients with SS have a poor prognosis (median survival of 4 years). Cytologic transformation from a low-grade lymphoma to a high-grade lymphoma sometimes occurs during the course of these diseases and is associated with a poor prognosis.[13,14] A retrospective analysis of 100 cases with large-cell transformation found reduced disease-specific survival with extracutaneous transformation, increased extent of skin lesions, and CD30 negativity. A common cause of death during the tumor phase is sepsis from Pseudomonas aeruginosa or Staphylococcus aureus caused by chronic skin infection with staph species and subsequent systemic infections.References
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