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. These histologic types of T-cell lymphomas are discussed in another PDQ summary. (Refer to the PDQ summary on Adult Non-Hodgkin’s 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.

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 greater than or equal to 10% of the body surface (T2), and finally to tumors (T3) that frequently undergo necrotic ulceration. SS is an advanced form of MF with generalized erythroderma (T4) and peripheral blood involvement at presentation. 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. 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.