According to the results obtained by the IgG avidity ELISA, all samples had avidity >40 before chemotherapy, but after the treatment, a positive case [1% (95% CI 0.2–5.6)] was identified in a patient with lymphoma whose IgM was also positive, with an IgG avidity below 40 that indicated reinfection with Toxoplasma (Table 2). This evidence concerns the gene CD40LG and lymphoma.