Myelodysplasia Cutis

Context.-Myelodysplasia cutis is an emerging concept in cutaneous neoplasia. Many of these cases were previously included under the umbrella of histiocytoid Sweet syndrome. However, with the advent of next -generation sequencing, cutaneous involvement by myelodysplastic syndrome is being increasingly recognized. Objective.-To review histiocytoid Sweet syndrome and myelodysplasia cutis and discuss our current understanding of these entities. Additionally, to discuss how next -generation sequencing can be applied in the evaluation of cutaneous infiltrates of immature histiocytoid cells. Data Sources.-The English -language literature from 2005 to 2023 on the topic of histiocytoid Sweet syndrome and myelodysplasia cutis was reviewed. Conclusions.-Biopsy specimens showing infiltrates of histiocytoid, immature myeloid cells may represent cutaneous involvement by myelodysplastic syndrome. Close clinical correlation is recommended in these cases. Recent studies suggest that next -generation sequencing is useful in separating myelodysplasia cutis from true histiocytoid Sweet syndrome. This distinction has important implications for patients.