Age: 71.0
Sex: M
Vaccine: FLU3, FLUX, FLUX, FLUX, FLUX
Symptoms: Fluorescent in situ hybridisation negative, Gene mutation identification test negative, Immunohistochemistry, Injection site erythema, Injection site hypersensitivity
Clinical narrative: Case number PHHY2015US079039, is an initial literature case report received on 26 Jun 2015. The author discussed in the article about Blastic plasmacytoid dendritic neoplasm (BPDN) or BPDN-like lesion presenting after influenza vaccination and resolving with topical high potency steroid. This report refers to a 71-year-old male patient. The patient had no significant medical history. No concomitant medication was reported. The patient was vaccinated with influenza vaccine (unknown manufacturer, batch number: not reported) in the left upper arm on an unknown date. Seven days after vaccination the patient developed five centimeter non-tender, erythematous, and scaling plaque with an indurated border on the left upper arm. The lesion appeared at the site of the vaccination. The patient denied systemic symptoms and any such reaction with previous vaccinations. The initial clinical suspicion was injection site hypersensitivity reaction. A punch biopsy was performed. The biopsy found an atypical dense lymphoid infiltrate in the papillary and reticular dermis. A grenz zone was present. The infiltrate shows prominent perivascular distribution. The individual lymphocytes had hyperchromatic nuclei with irregular nuclear contour and nucleoli. Crush artefact was present at the periphery of the biopsy section. Immuno-histochemical profiling found the lesion to be diffusely CD4 (+) and CD56 (+).  Most of the lesional cells were also CD123 (+) and TdT (+). Repeat CD123 staining found more intense and diffuse positivity. Admixed were rare CD79 (+) B cells. Tests for myeloperoxidase, CD34, MUM1, PAX5, CD3, CD10, CD21, kappa, and lambda were negative. Epstein Barr virus in situ hybridization results were also negative. In addition to these markers, an outside hospital found that the lesion was TCL 1 (+) and CD117 (-) and muramidase negative. After histologic and immune-profiling of CD4 (+) CD56 (+), TCL1, and CD123 (+) a diagnosis of BPDN was rendered. Differential diagnosis included extramedullary myeloid sarcoma and an acute leukemia with ambiguous lineage. Absence of myeloperoxidase excluded myeloid sarcoma, and absence of CD34, myeloperoxidase, CD117, and muramidase ruled out acute leukemia. This diagnosis was confirmed by a senior hematopathologist and at major cancer center. The patient was prescribed topical high potency steroid diflorasone diacetate 0.05%. At the 2-week follow up, the patient reported that the entire lesion had resolved with topical steroid treatment. Despite the lack of clinical evidence of disease, radiation therapy was delivered at the site. At the time of this report, bone marrow and blood involvement were not found and leukemia was excluded, but watchful follow-up was necessary. Seriousness of the events was not reported. Seriousness of the event Blastic plasmacytoid dendritic cell neoplasia was upgraded based on Novartis Important Medical Events list. The author concluded that based on the current standards a diagnosis of BPDN was made on biopsy. However, the atypical presentation and behavior of the case raises the question if the lesion was indeed a distinct presentation of BPDN that carries a good prognosis or was a BPDN-like reaction to the vaccination. At the time of this report, the benign clinical course of the case was highly uncharacteristic of BPDN. Regardless, given the possibility of true BPDN and the prognosis it carries any such lesion with characteristic histology and immunophenotype should be met with extreme suspicion and treatment measures appropriate to BPDN should be considered.