Immunocytochemical analysis of CNHCs with antibodies against the hematological marker CD45. Cellular aggregates (clusters) of non-hematological cells (CNHC) isolated from blood of patients with renal tumors by ScreenCell® filtration (A-C) with cytomorphological features of malignant (CNHC-MF) (A), uncertain malignant (CNHC-UMF) (B), and benign cells (CNHC-BF) (C) as previously defined . None of the CNHC are detected by CD45 antibodies, whereas single lymphocytes are CD45-positive (indicated by arrows in A and C). Examples of filter pores (8 μm in diameter) are marked by arrow heads (B). Single CNHC isolated by ScreenCell® filtration (D-F) with cytomorphological features of malignant (−MF) (D), uncertain malignant (−UMF) (E), and benign cells (−BF) (F) are CD45-negative. However, leucocytes are stained with CD45 antibodies (arrows in D and F).