Large Cell Transformation of Sézary Syndrome

Hyperdiploidy sometimes is found in mycosis fungoides–Sezary syndrome, but its diagnostic significance remains undefined. We report an unusual case of Sezary syndrome manifesting with leukemic large cell transformation. Conventional karyotypic analysis showed the presence of a near-tetraploid neoplastic clone. With dual-color cytometric analysis, we showed that the large Sezary cells were neartetraploid with a DNA index of 1.86, thereby demonstrating a direct relationship between cell size and ploidy. Comparative genomic hybridization further showed chromosomal imbalances that were not revealed on conventional karyotyping. Our findings suggest that hyperdiploidy may be a marker of large cell transformation, so that when this karyotypic abnormality is found in mycosis fungoides–Sezary syndrome, a search for such a complication is indicated. Mycosis fungoides is a malignant disorder of T-helper cells characterized by proliferation of CD3+ CD4+ CD8– small lymphocytes with cerebriform nuclei in the skin. The disease shows a slow progression, sometimes with progressive involvement of the lymph nodes, visceral organs, bone marrow, and blood (Sezary syndrome). 1,2 Large cell transformation can occur in mycosis fungoides–Sezary syndrome. In most cases, the large cell transformation is demonstrated in solitary tumor infiltrates involving the skin and visceral organs. 3,4 Although circulating large lymphoma cells sometimes can be found in Sezary syndrome, 5 a leukemic phase composed solely of large cells has not been reported. We describe the conventional and molecular cytogenetic findings of a case of Sezary syndrome manifesting with leukemic large cell transformation.