IRF8 may be a useful marker for blastic plasmacytoid dendritic cell neoplasm, especially with weak CD123 expression

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.

Blastic Plasmacytoid Dendritic Cell Neoplasm Presenting as a Mammary Gland Tumor in a Pediatric Patient: A Case Report

“…The cell nuclei are round or irregular, the chromatin is finely detailed, the cytoplasm is basophilic, devoid of granules, and can have characteristic pseudopodia and mirror-image morphology, or can present a lymphoma-like or primitive monocyte-like morphological type. 19,20 However, a study found that only 44.4% of patients had typical BPDCN pathological morphology, with the remainder exhibiting morphological diversity. 21 This case showed primitive cell morphology, the nuclei were quasi-circular, the nucleoli were prominent, partially distributed in clusters, some cells had pseudopodial-like protrusions in the cytoplasm, were stained bluer, and the morphology leaned towards lymphoma-like, which is not typical, necessitating differentiation with immunophenotypic features.…”