Background: Recently we published preliminary data on the presence of Cancer Associated Macrophage-Like cells (CAMLs) in a variety of malignancies and their clinical use in tracking cancer progression (Adams et al., PNAS 2014). This report is a follow-up in identifying and tracking CAMLs, with an emphasis on correlating clinical and pathological stage from baseline samples. Methods: This multi-institutional prospective pilot study consisted of 105 patient (pt) samples: Stage I-IV; breast (n = 34), prostate (n = 25), pancreatic (n = 39) and lung (n = 7). Evaluators were blinded to the source and stage of the pts. Additionally, 30 non-blinded healthy controls with no known malignant disease were analyzed. 7.5 mL of whole blood was collected; filtered by the CellSieve microfiltration assay; and stained with DAPI, CK 8/18/19, EpCAM and CD45. CAMLs were enumerated and identified as large multinucleated circulating myeloid cells (e.g. CD14+). We report CAML number at clinical stage in relation to healthy controls and compare with patient’s pathological stage. Results: CAMLs were identified in 98/105 samples (93%), ranging from 0-105 CAMLs per peripheral blood sample at baseline, while 0 were found in 30 healthy controls; Sensitivity = 93.3% (CI95% 87-97%) and Specificity = 100% (CI95% 88-100%). Pts with breast, prostate and pancreatic cancer underwent surgical procedures and pathologically staged (n = 98). The number of CAMLs at baseline had a weak association with clinical stage; stage I (8.7 per sample), Stage II (6.8), Stage III (16), Stage IV (26.1); R²= 0.82. However, the number of CAMLs at baseline highly correlated with final pathological staging; stage I (4.3), Stage II (6.3), Stage III (14), Stage IV (24.6); R²= 0.94. Conclusions: Our data suggests that 1) CAMLs are circulating immune cells specific to malignant disease and 2) the number of CAMLs is weakly associated with clinical stage but highly correlative with pathological stage in a variety of malignancies. These findings indicate that CAMLS may be a valuable supplement to current screening and staging procedures.