DP06 (P10) Blastic plasmacytoid dendritic cell neoplasm: two representative cases

Abstract

Abstract Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a malignant proliferation of plasmacytoid dendritic cells, representing <1% of primary cutaneous lymphomas. It most commonly presents in the skin and has a poor prognosis with median survival of 1 year. The fifth World Health Organization classification of haematolymphoid tumours encompasses two entities in plasmacytoid dendritic cell neoplasms: BPDCN and ‘mature plasmacytoid dendritic cell neoplasm associated with myeloid neoplasm’. We present two cases, one representing each subset. Our first case was a 58-year-old man who presented with an asymptomatic, rapidly progressive, skin coloured-to-ery­thematous and hyperpigmented firm papules, nodules and plaques over the trunk, upper limbs and face of 2.5 months’ duration. This was associated with loss of appetite, loss of weight and leucopenia (2180 cells μL–1). Skin biopsy revealed a grenz zone with pandermal infiltration by large cells with high nuclear:cytoplasmic ratio, vesicular nuclei and prominent nucleoli and frequent mitotic figures. Immunohistochemistry (IHC) was leucocyte common antigen (LCA)+ but CD3–, CD20–, myeloperoxidase (MPO)– and CD117–. Bone marrow biopsy showed a similar infiltrate of cells, but the peripheral blood smear and flow cytometry was within normal limits. Further IHC was CD4+, CD56+, CD43+ and CD123+, establishing a diagnosis of BPDCN, and the patient was initiated on the Hoelzer protocol with 80% clearance of lesions after two cycles of chemotherapy. The second case was a 60-year-old woman who presented with asymptomatic firm skin-coloured nodules on her scalp, trunk, extremities and oral mucosa, associated with a low-grade fever, fatigability, weight loss, generalized lymphadenopathy and hepatosplenomegaly of 4 months’ duration. Histopathology showed similar features to the first case, with IHC being negative for CD3, CD20, CD138 and MPO. However, cells were LCA+, CD4+, CD56+ and CD43+. Bone marrow showed 77% acute leukaemia blasts with a MPO+ result, establishing diagnosis of acute myeloid leukaemia, suggestive of a mature plasmacytoid dendritic cell neoplasm associated with myeloid neoplasm. To conclude, BPDCN is an aggressive neoplasm that commonly presents in the skin and should be suspected by dermatologists when screening IHC for lymphoid and myeloid cell lines is negative in a suspected case of leukaemia cutis. A panel of CD4/CD56/CD43/CD123 may be used to establish the diagnosis.