Nuclear and nucleolar ultrastructure of Sézary cells.

Sézary cells were studied in the peripheral blood and characteristic skin lesions of the Sézary syndrome and mycosis fungoides by transmission electron microscopy to obtain more information on their nuclear and nucleolar ultrastructure. Sézary cells contain nucleoli with nucleolonemas or ring-shaped nucleoli similar to those of lymphoblasts and mature lymphocytes. "Maturation asynchrony" of the nucleolus and cytoplasm was evident in some cells that contain large numbers of ribosomes and ring-shaped nucleoli and in other cells that contain nucleoi with nucleolonemas and few ribosomes. The maturation asynchrony of the nucleolus and the cytoplasm, the presence of mitochondrion-like inclusion bodies in the nucleus, and fusion of mitochondria with the nucleus in Sézary cells are ultrastructural abnormalities of this neoplastic lymphocytic variant. The presence of the intranuclear "mitochondrion-like" inclusion body and nuclear rodlets in Sézary cells were exceptional findings.