Circulating Sézary cells in the diagnosis of Sézary syndrome (quantitative and morphometric analyses).

Plastic-embedded circulating Sézary cells were examined in semithin and thin sections (assisted by the nuclear contour index-NCI). Eight cases of Sézary syndrome were analyzed as well as 11 controls (3 cases of widespread eczemas and 8 cases of erythroderma), 7 cases of mycosis fungoides, and 3 healthy individuals. Discriminating criteria between Sézary syndrome and benign diseases were sought: in addition to Sézary cells (NCI greater than 6.5) intermediate lymphocytes (5.0 less than NCI less than or equal to 6.5) proved to be helpful. Cases with Sézary syndrome were clearly differentiated when the following 3 ultrastructural criteria were fulfilled: (1) Sézary cells (SC) greater than 9%; (2) intermediate lymphocytes (IL) greater than 20%; (3) the sum of SC and IL greater than 37%. A good correlation between thin and semithin sections was obtained (correlation coefficient for Sézary cells r = 0.82). Usually the values of SC were slightly higher on thin sections. The diagnosis of SS can be made on semithin sections when the ultrastructural criteria are fulfilled. In this way 8 of 12 samples of Sézary syndrome were correctly classified. Therefore, semithin sections (studied by light microscopy) are recommended as a routine method in the diagnosis of cases suspected of Sézary syndrome, whereas thin sections (studied by electron microscopy) appeared to be necessary in problem cases only.