Immune-Related Pancytopenia Induced by Anti-PD-1 Therapy - Interrupt or Continue Treatment - The Role of Immunohistochemical Examination.

Immune checkpoint inhibitors (ICIs), including anti-cytotoxic T-lymphocyte antigen 4 (anti-CTLA-4) and anti-programmed death receptor-1/ligand-1 (anti-PD-1/anti-PD-L1) caused a breakthrough in oncology and significantly improved therapeutic outcomes in cancer patients. ICIs generate a specific reaction in T cells, directed against antigens on cancer cells, leading to their damage and death. Through similar or the same antigens, activated lymphocytes may also have a cytotoxic effect on healthy cells, causing development of specific adverse effects - so-called immune-related adverse events (irAEs). We present the case report of a 56 year old patient with disseminated melanoma. During treatment with immunotherapy (anti PD-1), neutropenic fever and pancytopenia occurred. Trepanobiopsy of the bone marrow was performed to determine the cause of pancytopenia. Histopathological assessment of bone marrow combined with immunophenotype investigations may explain the cause of hematological disorders occurring in the course of treatment with ICIs, and support the choice of an appropriate treatment, directly translated into positive outcomes.