Mycosis fungoides and the Sézary syndrome: pathology, staging, and treatment

Mycosis fungoides and the Sézary syndrome are forms of cutaneous T-cell lymphoma. Mycosis fungoides is an uncommon disease: only about 500 new cases are diagnosed in the United States annually. The median age of onset is 55 years and there is a 2:1 male predominance. The etiology of mycosis fungoides is unknown. Although occupational exposures have been implicated, case control studies fail to support this hypothesis. Mycosis fungoides is typified by cutaneous plaques which may evolve into tumors over the course of time. It is often preceded by a lengthy pre-mycotic phase prior to the time of definitive diagnosis. In its earliest diagnostic phase, there may only be slightly scaling patches with a limited distribution. Indurated lesions evolve into plaques, which may become more generalized in their distribution. As the severity of skin involvement increases, there is an increasing likelihood of spread to extracutaneous sites. The pathology of this disease is marked by involvement of the epidermis (Pautrier microabscesses). Immunologic studies characterize these cells as belonging to the helper T-cell subset. Genotypic analysis demonstrates monoclonal rearrangements of the T-cell receptors of the infiltrating cells. The staging system for mycosis fungoides considers the extent of skin involvement, presence of lymph node or visceral disease, and detection of abnormal cells in the peripheral blood. Patients with disease limited to the skin (90% of newly diagnosed cases) are treated best with topical or cutaneous therapies. Common modalities include psoralen photochemotherapy (PUVA), topical chemotherapy (nitrogen mustard) and total skin electron beam therapy. Both topical nitrogen mustard and electron beam therapy have good initial response rates (73% and 100%) and may achieve long-term disease-free survival, especially in patients with initially limited disease. Even if the response is incomplete or relapse occurs, substantial and very important palliation is generally achieved with topical therapy. Recurrent or resistant cutaneous disease will require the use of sequential topical treatment. The median survival time of patients who present with disease limited to the skin is greater than 10 years, and many deaths in this group are from intercurrent causes, especially in patients with limited or generalized plaque disease. If cutaneous tumors are present, the majority of these patients will eventually die from disease-related causes. The prognosis of patients who develop extracutaneous disease is exceedingly poor (median survival time, approximately 1 year).(ABSTRACT TRUNCATED AT 400 WORDS)