Epithelioid cell granulomas may be associated with several neoplasms. Lymphomas may mimic or are associated with epithelioid granulomas. In this article the authors report a child with granulomatous reaction in B cell non-Hodgkin lymphoma and intracardiac thrombosis. Although cancer alone is a risk factor for thromboembolism, thrombosis is a multifactorial disorder with both hereditary and acquired risk factors. This is the first reported case of intracardiac thrombosis with MTHFR A1298C and factor XIII V34L mutations together with granulomatous reaction in non-Hodgkin lymphoma.