On immunohistochemistry, atypical large-sized lymphocytes were positive for CD20 and EBER-ISH and negative for CD3, CD5, and CD10; the Ki-67 labeling index was high, the histopathological diagnosis was EBV-positive DLBCL, and the clinical diagnosis was MTX-LPD. The gene discussed is MKI67; the disease is disseminated peritoneal leiomyomatosis.