Gray-zone lymphoma. Examples of rare clinical manifestation.

Mediastinal gray-zone lymphoma (MGZL, lymphoma with features intermediate between classical Hodgkin lymphoma and diffuse large B-cell lymphoma) was declared as a separate entity in WHO classification of Tumors of Haematopoetic and Lymphoid Tissues in 2008 and 2017 years. Despite of similar pathomorphological characteristics between primary mediastinal B-cell lymphoma and Hodgkin lymphoma, clinical features and optimal therapeutic approach to MGZL are not clearly defined. Usually MGZL manifests with mediastinal lymphadenopathy, although extranodal lesions often occur (grey-zone lymphoma, GZL). Patients with MGZL have unfavorable prognosis, taking into account high rate of relapse. This article describes two cases of MGZL. First case manifested by arrhythmias due to primary heart involvement. In spite of cardiac failure antracycline-containing chemotherapy (6 courses of R-DA-EPOCH) it allowed to achieve a complete remission and resolving of arrhythmias. Second case was represented by metachronous tumors: primary mediastinal B-cell lymphoma at the time of disease onset and classical Hodgkin lymphoma, NS II, diagnosed after disease progression. Thus, we demonstrated two examples of MGZL that differ by clinical manifestation, response to chemotherapy, which emphasizes an importance of pathogenesis studying, and using of new therapeutic approaches.