We have compared the diagnostic accuracy of image-guided 25G-FNA (fine-needle aspiration) and imaging modalities in a group of 31 patients with solid space-occupying renal lesions. All patients had undergone total nephrectomy and histologic sections were available for review.By FNA there were 24 malignant diagnoses, I benign diagnosis, and 6 cases with yield inadequate for diagnosis. The FNA accuracy for malignancy was 100% with no false positive cases; cancer typing by FNA matched the final histologic diagnoses in 91.6% of cases. Sensitivity, specificity, positive predictive value, and negative predictive value were 80%, 14%, 80%, and 14%, respectively.Radiologically there were 26 diagnoses of malignancy, I of benignity, and 4 indeterminate lesions (IL). Accuracy for malignancy was 100%, with one false positive case; cancer typing matched the final histologic diagnoses in 84%. Sensitivity of imaging modalities was 86%, specificity 17%, positive predictive value 83%, and negative predictive value 20%. Four IL corresponded to renal cell carcinoma in the final histologic report: two IL had a previous diagnosis of malignancy by FNA, and the yield of two was inadequate for cytologic diagnosis.Both techniques have 100% accuracy for the diagnosis of malignancy. The sensitivity, specificity, positive predictive value, and negative predictive value of imaging techniques are slightly higher than those obtained by FNA. Imaging techniques and FNA of solid renal masses complement each other in IL and in nondiagnostic FNAs. Diagn. Cytopathol. 2008;36:8-12.' 2007 Wiley-Liss, Inc.Key Words: solid renal masses; fine-needle aspiration; needle biopsy; cytology; imaging techniques Fine-needle aspiration (FNA) has a well-defined and traditional role in the diagnosis and treatment of numerous conditions in almost every organ of the body. Its utility is undeniable in space-occupying lesions of various locations; however, the use of FNA in space-occupying lesions of the kidney has recently tended to be confined to specific clinico-pathological conditions, mainly because of the refinement of imaging techniques. [1][2][3][4][5][6] The purpose of this article is 3-fold: to assess the diagnostic accuracy of image-guided 25G-FNA and imaging modalities in a group of 31 patients with solid space-occupying renal lesions who later underwent total nephrectomy (TN) for histologic confirmation; to compare the diagnostic accuracy of the two techniques; and to investigate whether FNA provides valuable information for the clinical management of patients with solid renal masses. Material and MethodsBetween January 2000 and July 2006 a total number of 129 patients of our hospital had been referred to either image-guided 25G-FNA as preoperative diagnostic procedure of renal space-occupying lesions, or to some type of imaging modality for planning clinical management, or had been referred to both. Of these 129 patients, the 31 in whom image-guided FNA, imaging studies, and TN were available were chosen for the present study.The cytologic specimens of im...