Pediatric Blastic Plasmacytoid Dendritic Cell Neoplasm: A Case Report

Abstract

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive neoplastic process of precursor plasmacytoid dendritic cells. The diagnostic evaluation of this heterogenous entity is challenging, requiring a comprehensive approach of incorporating clinical, morphologic, immunohistochemical, and molecular/cytogenetic evaluations. Optimal management of BPDCN remains controversial, and clinical outcomes continues to be poor. Pediatric cases of BPDCN are rare and to our knowledge, this is the second case of BPDCN described in a Hispanic child, first one was described outside the US in Peru. Here, we report a case of a juvenile patient of Hispanic origin presenting with cutaneous and bone marrow involvement and initially misdiagnosed as a cutaneous infection that resulted in subsequent delaying of necessary chemotherapy for 2 months. Biopsy of the lesion showed diffuse infiltration of immature cells involving the dermis with classical sparring of epidermis. A huge panel of immunohistochemical stains were performed to reach the diagnosis of BPDCN. Staging bone marrow biopsy also revealed involvement by BPDCN. Treatment was not only delayed in this patient but also due to the rarity of BPDCN in pediatric population, the subsequent therapeutic decisions were challenging for the primary oncology team as it was based solely on published literature on adult population. Our case report will not only add one more case in the pediatric age group, but also will also emphasize that although BPDCN has a grave prognosis in the elderly, timely diagnosis with prompt treatment is the key to complete remission in pediatric BPDCN population.

Keywords: Blastic plasmacytoid dendritic cell neoplasm; Hispanic; mononuclear cells; plasmacytoid dendritic cells.

Figure 1.

(A) Case at presentation at outside institution showing red non-tender induration and (B) showing rapid progression of the lesion within 3.5 months during presentation to our institution with 10 × 11 cm indurated red-purple nodule with central atypical erosion.

Figure 2.

Skin punch biopsy of the right calf cutaneous lesion. (A) Low power view showing a diffuse atypical infiltrate sparing the epidermis and involving the dermis to the deepest aspect of the biopsy (H&E, ×20). (B) High power view showing the cells in the infiltrate are small to medium size with irregular nuclei, vesicular chromatin, inconspicuous nucleoli, and scant cytoplasm. Mitotic figures are frequently observed (yellow arrows indicating the mitotic figures). No necrosis noted. (H&E, ×400).

Figure 3.

Skin punch biopsy (×400): (A) immunohistochemical staining for CD56 showing diffuse positivity, (B) immunohistochemical staining for CD123 showing diffuse positivity, (C) immunohistochemical staining for TCL-1 showing diffuse positivity, and (D) immunohistochemical staining for TCF4 showing diffuse positivity.

Figure 4.

(A) Bone marrow trephine biopsy at diagnosis (H&E, ×1000), abnormal blastoid cells noted (yellow arrows) with immature morphology of high nuclear-cytoplasmic ratio, vesicular chromatin, and scant cytoplasm. (B) Bone marrow trephine biopsy at diagnosis (×400), immunohistochemical staining for CD123 reveals focal clustering of CD123+ cells. (C) Bone marrow trephine biopsy at diagnosis (×400), immunohistochemical staining for CD56 reveals focal clustering of CD56+ cells corresponding to abnormal cells seen on CD123 immunostaining. (D) Bone marrow trephine biopsy at diagnosis (×400), immunohistochemical staining for TCL1a.

Figure 5.

Flow cytometric analysis of a bone marrow aspirate sample at diagnosis. The abnormal blast population is positive for (A) CD45(dim), positive for (B) CD4+, CD123+, positive for (C) CD56++ and negative for CD34.

Figure 6.

Photograph showing postinduction regression of right calf cutaneous lesion: (A) Day 27 of induction therapy, (B) Day 8 of consolidation after completion of initial induction with alternating cycles of Tagraxofusp infusion, and (C) Day 22 of consolidation.