Comparative study of CT appearances in renal oncocytoma and chromophobe renal cell carcinoma

Background Renal oncocytoma (RO) and chromophobe renal cell carcinoma (ChRCC) share histologic and some imaging features. Purpose To investigate the multidetector computed tomography (MDCT) characteristics of these two tumor types. Material and Methods Fifty-six patients with RO and 54 patients with ChRCC were studied retrospectively. MDCT was undertaken to investigate differences in tumor characteristics. Results Calcifications were visible in 24 (42.8%) patients with RO and in 11 (20.4%) patients with ChRCC (P=0.011). 26 patients with RO had stellate scars as did 14 patients with ChRCC (P=0.025). Spoken-wheel-like enhancement was visible in 41 patients with RO and in 11 with ChRCC (P<0.001). Thirty-nine (69.6%) patients with RO and nine (16.7%) patients with ChRCC showed segmental inversion (P<0.001). Two patients with RO had retroperitoneal lymph node enlargement as did 13 patients with ChRCC (P=0.002). Combined evaluation of stellate scar, spoken-wheel-like enhancement, and segmental enhancement inversion features were found to have a sensitivity of 99.1% (106 of 107), a specificity of 100% (3 of 3), a positive predictive value of 100% (106 of 106), and a negative predictive value of 75% (3 of 4). The attenuation of RO tumors was greater than that of ChRCC tumors, normal renal parenchyma on unenhanced CT (P=0.031). Enhancement was higher with RO than with ChRCC tumors in all phases (P=0.021,<0.001, and 0.007, respectively). Conclusion CT imaging features such as stellate scar, spoken-wheel-like enhancement, and segmental enhancement inversion were more common in RO and they may help in differentiating RO from ChRCC.