Fawaz Al Harbi1,2, Leila Tabatabaeefar1, Michael A Jewett3, Anthony Finelli3, Martin O'Malley2, Mostafa Atri1. 1. 1 Department of Medical Imaging, University of Toronto, Toronto General Hospital, 585 University Ave, Toronto, ON M5G 2N2, Canada. 2. 2 Department of Medical Imaging, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada. 3. 3 Department of Surgical Oncology, Division of Urology, University of Toronto, Toronto, ON, Canada.
Abstract
OBJECTIVE: The objective of our study was to determine whether small (< 4 cm) solid renal cell carcinomas (RCCs) enhance on CT below the published enhancement thresholds. MATERIALS AND METHODS: For this retrospective study, we reviewed CT examinations of patients with pathologically characterized small solid renal masses. Patients with lipid-rich angiomyolipomas were excluded. The study included consecutive patients who had pathologically characterized small (< 4 cm) renal masses and had undergone CT during the un-enhanced phase and nephrographic phase (NP). Most CT examinations also included imaging during the corticomedullary phase (CMP); four patients did not have CMP images. The CT examinations were performed on a 64-MDCT scanner. Similar-sized ROIs were placed on each lesion on unenhanced and enhanced images and enhancement (in Hounsfield units) was calculated. Masses were considered solid with a threshold enhancement greater than either 15 or 20 HU. RESULTS: There were 137 masses in 137 patients, 90 men and 47 women (age range, 21-91 years; median age, 65 years). The renal masses were 1.0-3.9 cm (median, 2.4 cm). Of the 137 masses, 117 (85.4%) were malignant and 20 (14.6%) were benign. One malignant mass and three benign masses did not have CMP images. Twenty of the 116 (17.2%) renal cell carcinomas (RCCs) did not reach the 15-HU threshold enhancement on CMP images, nine of 117 masses (7.7%) did not reach the 15-HU enhancement threshold on NP images, and four of 117 masses (3.4%) did not reach the 15-HU enhancement threshold on both CMP and NP images. The numbers of masses that did not reach the 20-HU enhancement threshold were 24 of 116 masses (20.7%) on CMP images, 14 of 117 masses (11.9%) on NP images, and 11 of 117 masses (9.4%) on both CMP and NP images. Depending on the phase or enhancement threshold, 13.6-59.1% of papillary RCCs did not reach the enhancement threshold. CONCLUSION: A minority of small RCCs do not reach either a 15- or 20-HU enhancement threshold and might be misinterpreted as a hyperattenuating cyst. Most RCCs below these enhancement thresholds are papillary RCC.
OBJECTIVE: The objective of our study was to determine whether small (< 4 cm) solid renal cell carcinomas (RCCs) enhance on CT below the published enhancement thresholds. MATERIALS AND METHODS: For this retrospective study, we reviewed CT examinations of patients with pathologically characterized small solid renal masses. Patients with lipid-rich angiomyolipomas were excluded. The study included consecutive patients who had pathologically characterized small (< 4 cm) renal masses and had undergone CT during the un-enhanced phase and nephrographic phase (NP). Most CT examinations also included imaging during the corticomedullary phase (CMP); four patients did not have CMP images. The CT examinations were performed on a 64-MDCT scanner. Similar-sized ROIs were placed on each lesion on unenhanced and enhanced images and enhancement (in Hounsfield units) was calculated. Masses were considered solid with a threshold enhancement greater than either 15 or 20 HU. RESULTS: There were 137 masses in 137 patients, 90 men and 47 women (age range, 21-91 years; median age, 65 years). The renal masses were 1.0-3.9 cm (median, 2.4 cm). Of the 137 masses, 117 (85.4%) were malignant and 20 (14.6%) were benign. One malignant mass and three benign masses did not have CMP images. Twenty of the 116 (17.2%) renal cell carcinomas (RCCs) did not reach the 15-HU threshold enhancement on CMP images, nine of 117 masses (7.7%) did not reach the 15-HU enhancement threshold on NP images, and four of 117 masses (3.4%) did not reach the 15-HU enhancement threshold on both CMP and NP images. The numbers of masses that did not reach the 20-HU enhancement threshold were 24 of 116 masses (20.7%) on CMP images, 14 of 117 masses (11.9%) on NP images, and 11 of 117 masses (9.4%) on both CMP and NP images. Depending on the phase or enhancement threshold, 13.6-59.1% of papillary RCCs did not reach the enhancement threshold. CONCLUSION: A minority of small RCCs do not reach either a 15- or 20-HU enhancement threshold and might be misinterpreted as a hyperattenuating cyst. Most RCCs below these enhancement thresholds are papillary RCC.
Authors: Daniel R Ludwig; David H Ballard; Anup S Shetty; Cary L Siegel; Motoyo Yano Journal: AJR Am J Roentgenol Date: 2019-10-01 Impact factor: 3.959
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