Clinicopathological analysis of 46 cases with CD4 + and/or CD56 + immature haematolymphoid malignancy: reappraisal of blastic plasmacytoid dendritic cell and related neoplasms.

AIMS: In this study, we aimed to investigate the clinicopathological features of CD4+ and/or CD56+ immature haematolymphoid malignancy (iHLM), including blastic plasmacytoid dendritic cell neoplasm (BPDCN).

METHODS AND RESULTS: We analysed the clinicopathological features of 46 patients diagnosed consecutively with CD4+ /CD56+ iHLM. These cases were categorised into three groups based on their immunohistochemical expression of three plasmacytoid dendritic cell (pDC) markers [CD123, CD303 and T cell leukaemia/lymphoma (TCL1)]: cutaneous BPDCN (n = 35), non-cutaneous BPDCN (n = 6) and non-BPDCN-type CD56+ neoplasms (n = 5). Compared to non-cutaneous BPDCN, cutaneous BPDCN was associated with an older median age at onset (72 years versus 45 years, P < 0.05), and higher positivity for CD4 (P < 0.05), CD123 (P < 0.05) and 2-3 pDC markers (89% versus 50%, P = 0.05). Cutaneous BPDCN was divided into terminal deoxynucleotidyl transferase (TdT)+ and TdT- subgroups, which did not differ in prognosis, although TdT+ cases showed a lower median onset age (66 years versus 79 years, P < 0.05) and higher frequency of extracutaneous lesions (P < 0.05). Compared to the BPDCN groups, non-BPDCN-type CD56+ neoplasm cases showed higher cytoplasmic CD3 positivity (P < 0.05) and less frequent BCL-2 expression (P < 0.05), and lacked cutaneous lesions. However, the survival curves overlapped. Notably, one case involved an unusual composite neoplasm, comprising CD56+ lymphoblastic lymphoma and mature CD56+ cytotoxic T cell lymphoma.

CONCLUSIONS: Our present data support the recognition of cutaneous BPDCN as a homogenous entity, in contrast to the non-cutaneous form. Additional research is warranted to characterise non-BPDCN-type CD56+ neoplasms.