LAUSR

A 34yearold man with no known medical condition was vaccinated against SARSCoV2 in April 2021 using inactivated Vero cell vaccine (Sinovac). He experienced fever (39.5°C) on day 2 and on day 4 developed nasal cavity pain and a foulsmelling, yellow nasal discharge. There was improvement after antibiotic treatment. In June, he received the 2nd dose and developed similar symptoms. Nasopharyngoscopy showed a neoplasm in the nasopharynx with purulent secretion, necrosis and bleeding (top left). Endoscopic biopsy showed an atypical lymphocytic infiltration in the mucosa and adjacent muscle. Immunohistochemical analysis showed over 90% of cells to be positive for Epstein– Barr virusencoded small RNA (EBER), Ki67, CD3, CD56, CD5, TLA1 and granzyme B. These results supported the diagnosis of extranodal NK/Tcell lymphoma, nasal type. Positron emission tomography/computed tomography (PET/CT) showed a thickened wall of the nasopharynx and increased Ffluorodeoxyglucose (FDG) uptake (top centre and right). Because of diagnostic uncertainty, no treatment was accepted by the patient. From July to Nov 2021, he had three endoscopic examinations with no neoplasm being detected (bottom left). A followup PETCT similarly did not detect any tumour (bottom centre and right) while biopsy slides restaining showed the same pathological changes including lymphoma cell markers expression and EBER positive staining, confirming the initial diagnosis. Spontaneous remission of lymphoma after SARSCoV2 infection has previously been reported in follicular lymphoma and Hodgkin lymphoma. It has been speculated that the viral infection triggers a systemic antitumour immune response. The inactivated vaccine that our patient received could have mimicked the viral infection and led to antitumour immune activity. Whether the observed remission in this patient is a transient or a permanent recovery needs further followup. Together, these observations call for a reassessment of SARSCoV2 infection or vaccinationinduced immune response in lymphoma patients.