Correlation of CT Findings in Renal Cell Carcinoma with Nuclear Grading and Cell Type

Abstract

Purpose: To evaluate the CT appearances of renal cell carcinoma and correlate them with the nuclear grading and cell type which had been reported as important long term prognosticators. Materials and Methods: Retrospective review of contrast enhanced CT scans was performed in 86 cases of pathologically confirmed renal cell carcinoma. The size, outer margin, and heterogeneity of inner texture of the tumor were evaluated by CT and the distribution of those patterns according to nuclear grade and cell type was compared. The size of the neoplasm was determined by measuring the maximum axial diameter. The shape of the outer margin was classified as sharp or indistinct. The sharply marginated tumors were subclassified as no protrusion, round protrusion, and undulated protrusion. The inner texture was classified as homogeneous solid and heterogeneous containing low density areas. Lesions of the latter type were subclassified as having focal low densities, scattered or confluent low densities, and nearly cystic appearance. Results: The size and outer margin of the tumor were closely correlated with nuclear grade(p<0.01). The tumors less than 5 cm in diameter were of low nuclear grade in 28 of 31 patients. However, the tumors more than 5 cm in diameter were low grade in 28 and high grade in 27 patients. There was a statistically significant difference in distribution of nuclear grading between the two groups (p=0.0002). The lesions which showed no protrusion or round protrusion with sharp margin were low grade in 26 of 28 patients. The lesions which showed undulated or indistinct margin were low grade in 30 and high grade in 28 patients. There was a statistically significant difference in distribution of nuclear grading between the two groups (p=0.0008). The extent of low densities and nuclear grade were not closely correlated(p>0.05). However, the lesions which showed homogeneous solid appearance, focal low densities, or almostly cystic appearances were low grade in 23 of 26 patients while the lesions which showed multiple or confluent low densities were low grade in 33 and high grade in 27 patients. There was a statistically significant difference in distribution of nuclear grading between the two groups(p=0.002). No difference in CT apperances of renal cell carcinoma according to cell type was found. In two patients with sarcomatoid-type lesions, the tumors were more than 5 cm in size with indistinct margin and multiple low densities, and the nuclear grading of lesions was nuclear grade 4. Conclusion: The size and outer margination of renal cell carcinoma correlated most closely with nuclear grading.