Of the 168 patients with history of cancer who were asymptomatic for Covid-19, 29 cases (17.26%) had positive serological test, as follows: three patients (1.78%) were positive for both IgG and IgM, 24 patients (14.28%) were IgG positive and IgM negative, two patients (1.19%) were IgM positive and IgG negative. The gene discussed is CD40LG; the disease is cancer.