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.