A misdiagnosed case of blastic plasmacytoid dendritic cell neoplasm experiencing multiple recurrences who underwent allogeneic stem cell transplantation: a case report.

Background: Blastic plasmacytoid dendritic cell neoplasm represents a rare type of hematologic malignancy that often manifests itself through various skin lesions. It commonly affects the elderly male population. Lymph nodes, peripheral blood, and bone marrow involvement are the typical findings that justify its aggressive nature and dismal prognosis. On histopathological assessment, malignant cells share some similarities with blastic cells from the myeloid lineage that make immunohistochemistry staining mandatory for blastic plasmacytoid dendritic cell neoplasm diagnosis.

Case Presentation: A 35-year-old Asian man presented with cervical lymphadenopathy followed by an erythematous lesion on his left upper back. At first, the lesion was misdiagnosed as an infectious disease and made the patient receive two ineffective courses of azithromycin and clarithromycin. Six months later, besides persistent skin manifestations, he felt a cervical mass, which was misdiagnosed as follicular center cell lymphoma. Tumor recurrence following the chemoradiation questioned the diagnosis, and further pathologic assessments confirmed blastic plasmacytoid dendritic cell neoplasm. The second recurrence occurred 3 months after chemotherapy. Eventually, he received a bone marrow transplant after complete remission. However, the patient expired 3 months after transplant owing to the third recurrence and gastrointestinal graft versus host disease complications.

Conclusions: Early clinical suspicion and true pathologic diagnosis play a crucial role in patients' prognosis. Moreover, allogenic bone marrow transplant should be performed with more caution in aggressive forms of blastic plasmacytoid dendritic cell neoplasm because of transplant side effects and high risk of cancer recurrence.