IRF8 may be a useful marker for blastic plasmacytoid dendritic cell neoplasm, especially with weak CD123 expression
Haiming Tang1, Gauri Panse1, Demetrios Braddock1
1Department of Pathology, Yale School of Medicine, New Haven, Connecticut, USA.
Insights
Interferon regulatory factor 8 (IRF8) aids in diagnosing blastic plasmacytoid dendritic cell neoplasm (BPDCN), especially when CD123 expression is weak. IRF8 is a valuable marker for BPDCN, improving diagnostic accuracy in challenging cases.
Area of Science:
- Hematology
- Oncology
- Immunology
Background:
- Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy.
- Accurate diagnosis can be challenging due to variable immunophenotypic expression.
Observation:
- A case of BPDCN presented with skin nodules and atypical mononuclear cells.
- Initial immunophenotyping showed mixed and atypical marker expression, complicating diagnosis.
- Retrospective IRF8 staining was strongly positive in neoplastic cells.
Findings:
- Interferon regulatory factor 8 (IRF8) is a novel marker for monocytic and dendritic cell lineages.
- IRF8 demonstrated uniform strong positivity in 15 BPDCN cases, including those with dim or negative CD123.
- CD123 and TCL-1 expression can be weak or variable in BPDCN, posing a diagnostic pitfall.
Implications:
- IRF8 is a useful diagnostic marker for BPDCN, particularly in cases with atypical immunophenotypes.
- This finding can improve diagnostic accuracy and patient management for BPDCN.
- Further research into IRF8 utility in BPDCN is warranted.
Abstract:
We highlight the utility of interferon regulatory factor 8 (IRF8), a novel marker of monocytic and dendritic cell lineages, in the diagnosis of a case of blastic plasmacytoid dendritic cell neoplasm (BPDCN) presenting initially in the skin. A 60-year-old male with a previous history of myelodysplastic syndrome presented with cutaneous nodules on chest and scalp. A punch biopsy specimen of a skin nodule showed a diffuse dermal infiltrate of atypical mononuclear cells. The neoplastic cells expressed CD4, CD56, CD43, and TdT but showed minimal reaction for TCL-1 and CD123, and were negative for CD34, CD117, and MPO, confounding the diagnosis. IRF8 performed in retrospect was strongly positive. A new punch biopsy specimen of a chest nodule showed the blastoid tumor cells were positive for TCL-1, CD4, and CD56, but dim CD123. Subsequent bone marrow involvement showed blastoid tumor cells with intense positivity for CD123, CD4, and CD56, which was supportive of the BPDCN diagnosis. BPDCN cases with weak or variable CD123 and TCL-1 expression represent a potential diagnostic pitfall. In a recent study, 15 cases of BPDCN showed uniformly strong staining for IRF8, while CD123 was dim or negative in 4 of these 15 cases. We suggest IRF8 may be a useful marker for BPDCN, especially in cases with weak or variable expression of CD123 and TCL1.
