Cytologic transformation in cutaneous T cell lymphoma: a clinicopathologic entity associated with poor prognosis.

The clinical course of cutaneous T cell lymphoma (mycosis fungoides and Sezary syndrome) is generally indolent, but in occasional patients becomes fulminant. We found that biopsies from patients with accelerating disease can reveal cytologic transformation from previously observed small, convoluted lymphocytes to large cells that are similar to cells seen in large-cell lymphoma. The cerebriform nuclei characteristic of malignant T cells can only rarely be identified. Of 150 cutaneous T cell lymphoma patients we treated from 1976 to 1984, cytologic transformation was identified in 12 after review of peripheral blood smears and biopsies from skin, lymph nodes, and visceral sites. Patients who developed cytologic transformation were initially characterized by advanced stage (11 of 12), with lymph node effacement (seven of 11) and erythroderma (five of 12). The tumor cell DNA content after transformation was aneuploid (four of four), and the ability to form rosettes with sheep erythrocytes was retained in transformed cells (three of three). The median time from diagnosis of cutaneous T cell lymphoma to cytologic transformation was 21.5 months (range, 4 to 64), and the median survival from transformation was only 2 months (range, 0 to 19+). We conclude that cytologic transformation in cutaneous T cell lymphoma represents a distinct clinicopathologic entity, characterized by an aggressive clinical course.