CD4+ CD56+ blastic tumor of the skin: cytogenetic observations and further evidence of an origin from plasmocytoid dendritic cells.

We here report on a case of a blastic tumor, recently described to belong to a new entity sharing phenotypic similarities with blood derived plasmocytoid dendritic cells and formerly regarded as belonging to the group of natural killer cell lymphomas. Besides immunophenotypic characteristics such as the absence of T- cell markers and almost complete absence of markers of the myeloid lineage, these tumors express CD4, CD56 and CD123, the receptor for interleukin-3. Moreover, using the comparative genomic hybridisation technique, CGH, we demonstrate a gain of chromosome 7q, 22 and a loss of chromosome 3p and 13q. Since this type of hematologic disorder often shows its primary manifestation in the skin and often runs a rapidly fatal course, it is important to distinguish this from other types of primary cutaneous lymphomas.