Gray zone lymphomas in pediatric patients.

Gray zone lymphomas are defined as lymphoid malignancies that cannot be reliably classified into a single distinct disease entity after all available morphologic, immunophenotypic, and molecular investigations have been performed. The 2008 World Health Organization Classification proposed 2 gray zone lesions: (1) B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma and (2) B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma. These gray zone lesions are rare, especially in pediatric patients, and create a great challenge to both pathologists and oncologists because this differential diagnosis has direct implications for management strategies. In this manuscript, we report 2 cases of pediatric patients with gray zone lymphoma and review clinicopathologic features, treatment options, and outcomes of this uncommon tumor.