Introduction. The expanded use of imaging technology has led to improvements in the early diagnosis of kidney cancer. However, providing correct diagnoses regarding the malignant potential of small renal lesions remains problematic for clinicians. In addition to imaging, pre-operative investigations usually include a complete blood count and biochemistry tests. Aim of the study. To evaluate whether the pre-operative blood cell count, cell ratios, C-reactive protein (CRP) levels, and erythrocyte

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... sedimentation rate (ESR) can be helpful in predicting the malignancy of visually suspicious renal masses prior to surgery. Material and methods. Data on pre-operative blood tests were retrospectively collected from 84 cases of stage I renal cell carcinoma (RCC) and 55 benign lesions from patients hospitalized after a radiological finding of renal cancer and following nephrectomy. The predictive ability of various blood tests for malignant potential was analysed using the following statistical methods: the Mann- Whitney U test, receiver operating characteristic (ROC) curves and binary logistic regression. Results. The mean CRP levels, monocyte (Mo) counts, platelet (PLT) counts and monocyte/lymphocyte ratios (MLRs) varied significantly between the patients with stage I RCC and patients that had benign renal lesions with a small effect size. Among these tests, the highest AUCs were displayed by CRP [0.704, 95% confidence interval: 0.567 - 0.807] and MLR [0.736, 0.612 - 0.861]. Based on the ROC curves, optimal cut-off values of 0.26 for MLR and 1.75 mg/L for CRO were selected. A binary logistic regression was used to determine if the combination of CRP and MLR could be used to predict whether patients with renal lesions had cancer resulting in increase of area under the curve (AUC) to 0.798 [0.690 -0.905]. Conclusions. In cases of diagnostic difficulties observing small renal lesions radiologically, the combination of elevated CRP levels and MLRs above 0.26 may help to confirm the presence of renal cancer.