Circulating Sézary cells. A new preparatory method for their identification and enumeration.

Although Sézary cells are not specific for the Sézary syndrome, the enumeration of these circulating abnormal lymphoid cells is important in the evaluation of patients with mycosis fungoides, Sézary syndrome, and benign dermatoses that might be confused with these entities. Various techniques have been developed for this purpose, but none of the techniques have been widely accepted as practical and accurate. We describe a new method of preparing blood specimens for the identification and enumeration of circulating Sézary cells. Peripheral blood was separated on a density gradient and the mononuclear cell fraction was embedded in plastic. Semithin sections were cut, stained for alpha-naphthyl acetate esterase, and examined by light microscopy. We found that the percentage of Sézary cells correlated well with the clinical diagnosis of Sézary syndrome in the subjects who were studied.