Regressing Atypical Histiocytosis: The Controversy Continues-Reply

In Reply.—  We find nothing controversial in Dr Dehner's comments. In fact, we are delighted to have such an excellent critical appraisal. We are particularly grateful for the detailed follow-up of the original two patients with regressing atypical histiocytosis.We agree that the myeloid monocyte is not a cytologic sanctum sanctorum for neoplastic transformation, but that was not the point of our study. We also agree that additional studies could have been done with respect to immunophenotyping for cells of possible monocyte origin; however, this comment could be made on a daily basis with respect to the explosive increase in numbers of both commercial and private antibodies available for study. We feel confident, within the limits of the technology available to us at this time, that our patient had a monoclonal T-cell proliferation. It should be perfectly obvious that "clonality" does not establish cell lineage, but it is difficult to discount the