Measuring Lymphocytes-Reply

In Reply.—  The strength of our laboratory evaluation of cutaneous T-cell lymphomas lies in the combined approach of using histology, immunohistochemistry, and ultrastructural morphometry.¹ McNutt disagrees, however, as to the way the ultrastructural morphometry was performed, specifically, the evaluation of cells based on chromatin patterns. He specifies that blast transformation and abnormal blastic forms can provide important clues to the diagnosis of mycosis fungoides (MF). Blast transformation is, indeed, an important clue in the diagnosis of MF but, in our laboratory, blast transformation is evaluated using immunohistochemistry and histology, not electron microscopy.' The specific immunophenotype of blast cells is crucial to the distinction between MF and peripheral T-cell lymphoma, the latter of which can have a most aggressive course.²In our experience, electron microscopy is most useful in evaluating lymphoid infiltrates that, at the light microscopic level, are morphologically consistent with either early MF or chronic dermatitis (ie, mature