Even though the effective rate of asymptomatic COVID-19 in patients affected by solid tumors is suboptimally assessed through SARS-CoV-2 serology, as no NPS actually detected viral RNA in any IgM+ patient, the seroprevalence of SARS-CoV-2 IgM in this population reflects the incidence of asymptomatic COVID-19 in the general population during the first wave of COVID-19 pandemic. Here, CD40LG is linked to COVID-19.