C3 and hematopoietic and lymphoid cell neoplasm: In comparison with patients who developed solid cancer, those who developed hematological cancer had a higher frequency at diagnosis of cryoglobulins (p = 0.002), low C3 levels (p = 0.018), high ESSDAI score (p = 0.001), and high DAS (p < 0.001) (Additional file 1: Table S1).