Transformation of low-grade follicular lymphoma to a high-grade follicular lymphoma with the histopathological diagnosis from oral biopsy: a case report - Gabriela Silveira de Araujo; Leandro Dorigan de Macedo; Alfredo Ribeiro-Silva; Hilton Marcos Alves Ricz; Lara Maria Alencar Ramos Innocentini (Hematology, Transfusion and Cell Therapy)