Immunological Senescence Phenotype as a Resistance Profile to Pembrolizumab in Patients With Relapsed/Refractory Hodgkin's Lymphoma

This is a single-centre, observational, prospective and exploratory study, which involves the use of human tissues from patients affected by Relapsed/Refractory classic Hodgkin Lymphoma treated with pembrolizumab at the Departmental Diagnosis and Therapy program for chronic lymphoproliferative syndromes of the IRCCS AOU of Bologna. Peripheral blood samples will be used for the study and will be taken: * before starting treatment with pembrolizumab. * undergoing therapy with pembrolizumab (cycle 2 (C2), C3, C4, C8, C12).