CD4-negative variant of CD4+/CD56+ hematodermic neoplasm: description of three cases.

Background: CD41/CD561 hematodermic neoplasm (HN) (blastic natural killer (NK)-cell lymphoma) is a rare entity characterized by dense, monomorphous infiltrates of medium-sized cells with blastic appearance and a characteristic immunophenotype (positivity for CD4, CD56 and CD123). The combination of CD4 and CD56 positivity is thought to be so striking that it has been used to name this entity. Methods: Three cases of HN with ambiguous phenotypic profile were included in this study. In all cases, phenotypic, molecular and in situ hybridization studies were carried out. Results: All three cases showed an aberrant phenotype with negativity for CD4. Conclusions: CD4-negative or CD56-negative cases of HN have been rarely reported in the literature and represent a diagnostic problem. Our three cases confirm that CD4 is not always expressed in these neoplasms. The term ‘CD41/CD561 hematodermic neoplasm’ adopted in the World Health Organization–European Organization for Research and Treatment of Cancer classification of cutaneous lymphomas may be misleading and should probably be revised in the light of all data published in the literature.