Newly diagnosed extranodal NK/T-cell lymphoma, nasal type, at the injected left arm after BNT162b2 mRNA COVID-19 vaccination.

Anti-SARS-CoV-2 vaccines were developed in response to the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the BNT162b2 mRNA vaccine is effective, adverse effects have been reported. Here, we report a case of extranodal NK/T-cell lymphoma, nasal type (ENKL), of the left arm following BNT162b2 mRNA vaccination. A 73-year-old male presented with a lump in the left arm, which was the site where he received the BNT162b2 mRNA vaccine 3 months prior. He was treated with topical corticosteroids and debridement, but the tumor progressed. Additionally, fever, night sweats, and general fatigue were observed. Laboratory findings included thrombocytopenia, elevated lactate dehydrogenase, and soluble interleukin-2 receptor levels. Skin biopsy led to a diagnosis of ENKL. The patient was treated with a 50% dose of SMILE therapy and radiotherapy, resulting in regression of the tumor. It seems that latent Epstein-Barr virus (EBV)-infected NK/T cells were reactivated by vaccination and contributed to the onset of ENKL. This is the first report of ENKL after BNT162b2 mRNA vaccination. The present case highlights the possible risk of development of malignant lymphoma, including ENKL at the injection site, after BNT162b2 COVID-19 vaccination.