The pathological distinction between "deep penetrating" dermatofibroma anddermatofibrosarcoma protuberans

In selected cases, the clinicopathological distinction between deep penetra ting dermatofibroma (DPDF), which involves the subcutis, and dermatofibrosa rcoma protuberans (DFSPs) may be challenging, In most instances, attention to the cytological constituency of the lesions and the overall architecture is sufficient to make this separation, DPDF is typified by cellular hetero geneity, including giant cells and lipidized histiocytes; when it extends i nto the hypodermis, it does so either using the interlobular subcuticular f ibrous septa as scaffolds or in the form of broad pushing fronts of tumor, In contrast, DFSP is a cytologically monotypical tumor, which entraps subcu taneous adipocytes diffusely or grows in stratified horizontal plates in th e hypodermis, In the minority of cases where conventional morphological ana lysis of optimal biopsy specimens is diagnostically indeterminate, immunost aining for CD34 and factor Xllla (FXllla) is helpful; it is also often nece ssary when a poorly-representative sample of the lesion has been obtained b y the clinician. Characteristically, DF is diffusely FXllla reactive and CD 34-negative, whereas DFSP manifests the converse of those findings, Other m arkers such as Ki-M1p, mutant p53 protein, and metallothionein may also pro vide adjuvant diagnostic information in this context, as may the observatio n of abnormalities in chromosomes 17 and 22 by direct karyotypic analysis. Copyright (C) 1999 by W.B. Saunders Company.