PTX3 and nonpapillary renal cell carcinoma: In clear cell Renal Cell Carcinoma (ccRCC), tumor cells produce C1r and C1s and use C1q secreted by macrophages, in order to form a functional C1 complex and activate the classical pathway in IgG-containing deposits [23] or on cell-bound pentraxin 3 (PTX3) [32].