Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive hematological malignancy that is derived from the precursors of plasmacytoid dendritic cells. Although BPDCN typically manifests in the skin, it can also evolve into a leukemic form or be complicated by acute myeloid leukemia, and some cases involve preceding myelodysplastic syndrome. We report the case of a 73-year-old Chinese man who presented with 2-year-old erythematous papules on his prothorax and back. Skin biopsy and immunohistochemistry revealed that the cells exhibited an immature blastic appearance (positive for CD4, CD123, and CD56, and negative for CD2, CD3, and CD20), which indicated a diagnosis of BPDCN. Due to his age, the patient was treated using methylprednisolone (20 mg/m2/day on days 1-7), which was followed by a mini-CHOP regimen (cyclophosphamide, doxorubicin, vincristine, and prednisone). We observed a significant treatment effect, and report this case to describe and discuss our experience with this successful treatment.