Monkeypox virus cytologic findings: An institutional experience with an emerging threat.

OBJECTIVES: Mpox is a viral disease caused by monkeypox, a highly contagious orthopoxvirus that resulted in a global outbreak beginning in spring 2022. Diagnosis is confirmed via polymerase chain reaction (PCR) testing of swabs from mucocutaneous lesions. Rare reports have documented the histologic changes of mpox lesions, but the cytologic features have not been described. We present the cytology findings of samples taken from swabs of mucocutaneous mpox lesions in 3 different patients. METHODS: The patients were all male, aged 55, 43, and 37 years, all with mpox confirmed by PCR testing. Swabs from chest (cases 1 and 2) and tongue (case 3) lesions were directly sampled and submitted in Aptima (case 1) or PreservCyt solution (cases 2 and 3). Liquid-based preps were prepared and stained using the Papanicolaou method. Specimens were assessed for viral cytopathic changes. RESULTS: All cases showed nuclear cytopathic changes (enlarged nuclei with open chromatin and prominent red nucleoli), 2 cases demonstrated multinucleated keratinocytes, and 1 case showed potential Guarnieri bodies. The chromatin margination and nuclear molding typical of herpesviruses was not appreciated. CONCLUSIONS: The cytopathic changes of monkeypox are not specific, but their recognition could prompt appropriate PCR testing. Monkeypox shows distinct cytologic changes compared with herpesviruses.