Comparative study between ultrasonographic and pathohistological findings of small renal cell carcinoma: Especially concerning echogenicity of renal cell carcinoma

We evaluated 12 cases of small renal cell carcinoma without necrosis or hemorrhage, especially concerning their echogenicity in relation to cell types, grading of cellular atypia, amount of stroma, and architectural arrangement. Among the twelve cases, 4 cases were hyperechoic and 8 cases were isoechoic. No hypoechoic lesion was found in this series. There were no meaningful differences in cell types or in the grading of cellular atypia between the hyperechoic type and the isoechoic type. In regard to the amount of stroma, all cases were of the medullary type, so this factor did not contribute to the difference of echogenicity in this series. Concerning the architectural arrangement the isoechoic types consisted of only the alveolar type, while the hyperechoic types were of the tubular type, the papillary type or the alveolar type coexisting with the diffusely scattered cytic type. It is suggested that the alveolar types would be isoechoic, while the tubular, papillary or cystic types would be hyperechoic. These results suggest that cellular factors such as cell types or the grading of cellular atypia may not affect the echogenicity of renal cell carcinoma, but that structural factors such as the architectural arrangement may affect it. Cavitary components of approximately 30-60 μ in diameter were found to be common in the structure of the hyperechoic types. We propose that a standard classification of echogenicity should be determined to facilitate discussion of the relation between echogenicity and pathohistological findings.