We report the case of a 46-year-old male patient presenting with a Claude Bernard-Horner Syndrome. Clinical evaluation showed a clonal B-cell population, lambda restricted. PET-scan captured femoral and axillary lymph nodes. Therefore the diagnosis of a marginal zone lymphoma was posted for which an attitude of watchful waiting was suggested. Eighteen months later, the patient developed an inguinal adenopathy. This lymph node led to the diagnosis of a nodular sclerosing Hodgkin lymphoma. Initial treatment with ABVD showed a good response, but the patient relapsed after eight months. A second biopsy confirmed the diagnosis of a marginal zone lymphoma but also identified giant Reed-Sternberg cells, (CD15+, CD30+ and CD20+). The initial biopsy was revised. This last diagnosis of a nodal marginal zone lymphoma with presence of Reed-Sternberg cells is rarely described in the literature. Several scientific theories can be found. Some cases described a transformation of non-Hodgkin lymphoma that presented Reed-Sternberg cells, other cases mentioned a collision or composite tumor. An accidental finding of Reed-Sternberg cells can be seen by after an infectious disease such as EBV. The presence of only Reed-Sternberg cells in a non-Hodgkin lymphoma is not sufficient to make a diagnosis of collision tumor. Copyright © 2020. Published by Elsevier Masson SAS.