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Imaging
1774
IMAGING
Imaging CA9 Level in Renal Cyst Fluid: A Possible Molecular Diagnosis of Malignant Tumours G. Li, G. Feng, M. Cuilleron, A. Zhao, A. Gentil-Perret, M. Cottier, C. Genin and J. Tostain Department of Urology, North Hospital, CHU of Saint-Etienne, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France Histopathology 2009; 54: 880 – 884.
Aims: The preoperative differentiation of malignant renal cystic tumours from benign lesions is critical, and it remains a common diagnostic problem. The aim was to examine if the Carbonic anhydrase 9 (CA9) level in cyst fluid can provide a molecular diagnosis of malignant cyst. Methods and Results: Twenty-eight patients with a cystic renal mass were included. Fine-needle aspiration was performed to obtain the fluid. Postoperative pathology confirmed that there were 16 cystic renal cell carcinomas. Twelve benign cystic tumours were used as controls. One hundred microlitres of supernatant of cyst fluid was used to measure the CA9 protein level, which was measured by an enzyme-linked immunosorbent assay technique. CA9 was strongly detected and considered as positive in the cyst fluid of all 16 cystic malignant tumours (⬎1000 pg/ml), whereas its expression was negative in 11/12 benign cystic tumours (⬍300 pg/ml). The difference in percentages of positive CA9 between malignant and benign renal cystic tumours was significant (P ⬍ 0.001). Conclusion: The fluid of malignant cystic renal tumours contains a high level of CA9 protein. The measurement of CA9 level in cyst fluid may be used as a molecular diagnosis for differentiation between malignant and benign renal cystic masses. Editorial Comment: Cystic renal lesions are common. However, differentiating benign renal cysts from malignant cysts is difficult. Often radiologists are reluctant to aspirate renal cysts because 1) the cyst aspirate results may be misleading and 2) post-aspiration followup imaging will be confounded by the intervening procedure. These authors explore using CA9 level as a specific marker for cystic renal cell carcinoma. A total of 28 cystic renal tumors were studied—16 cystic renal cell carcinomas and 12 benign cystic tumors that were used as controls. The authors theorize that pathological changes in the cyst wall may alter the composition of cyst fluid. Malignant renal cyst fluid will contain tumor proteins shed from the tumor cells. Since solid clear cell carcinomas and the majority of papillary carcinomas are CA9 positive, perhaps they will shed these markers in the cystic fluid. Using computerized tomographic guidance, an 18 gauge needle was placed in the cystic mass and fluid was aspirated. The volume of fluid varied from 1 to 80 ml. In this series all of the cystic renal cell carcinomas were CA9 positive. Of the 12 benign cysts 11 had absence or a low level of CA9. The study produced a sensitivity of 100% and a specificity of 92%. These authors note that the CA9 ELISA kit is now commercially available. I suspect that this CA9 information will be extremely helpful, and when assessed in conjunction with the cytology of the cyst fluid and the radiology features of the cyst it will improve our diagnostic accuracy. Cary Siegel, M.D.
IMAGING
1775
Kidney Neoplasms: Renal Halo Sign After Percutaneous Radiofrequency Ablation—Incidence and Clinical Importance in 101 Consecutive Patients T. C. Schirmang, W. W. Mayo-Smith, D. E. Dupuy, M. D. Beland and D. J. Grand Department of Diagnostic Imaging, Rhode Island Hospital and Warren Alpert Medical School of Brown University, Providence, Rhode Island Radiology 2009; 253: 263–269.
Purpose: To describe the incidence and clinical importance of the renal halo sign after percutaneous radiofrequency ablation (RFA) of renal neoplasms. Materials and Methods: Institutional review board approval was obtained for this HIPAA-compliant retrospective study. The study population consisted of 101 consecutive patients with 106 solid renal neoplasms that were treated with percutaneous RFA. Postablation computed tomographic (CT) and magnetic resonance (MR) images were retrospectively reviewed by three board-certified radiologists to determine the presence of the renal halo sign. Statistical analyses were performed to determine reader agreement and assess the effect that tumor size and location, radiofrequency (RF) applicator type, RFA treatment time and success, maximum RFA treatment temperature, and number of RF applications performed had on development of the renal halo sign. Results: The renal halo sign developed in 79 (75%) of the 106 ablated tumors. Average imaging follow-up lasted 25 months (range, 1–98 months). The renal halo sign appeared, on average, 6 months (range, 1 month to 3 years) after RFA. The renal halo sign resolved in five (6%) of 79 tumors treated. Interobserver agreement for the presence of the renal halo sign was high. Tumor size and location, RF applicator type, RFA treatment time and success, maximum RFA treatment temperature, and number of RF applications performed were not independent predictors of renal halo sign development. Conclusion: The renal halo sign is seen in 75% of patients after percutaneous RFA of renal neoplasms. It may decrease in size over time; however, it rarely disappears. It is important to recognize this sign, as it can be mistaken for recurrent tumor or angiomyolipoma by radiologists who are not familiar with RFA. Editorial Comment: Image guided tumor ablation is becoming more popular for treatment of patients with renal neoplasms. Understanding the postoperative appearance in patients who have undergone either RF ablation or cryoablation is essential for the radiologist, since some of the postoperative appearances can initially seem peculiar and be misinterpreted as residual or recurrent disease. The renal halo sign is one of these features commonly seen in patients who have undergone RF ablation. The authors describe the renal halo sign as a rim of macroscopic fat that surrounds at least 50% of the treated tumor. The fat is then surrounded by a thin rim of fibrosis. The halo is typically thin and defines the margin from the ablated tumor bed and the surrounding perinephric fat. The renal halo sign can be seen on CT and MR imaging. The renal halo encompasses a centrally treated tumor (which, if treated effectively, will not enhance on post-contrast studies), and is typically bright on T1-weighted images and dark on T2-weighted images. The authors found no correlation between the presence of the renal halo sign and the original tumor size. Urologists and radiologists should become acquainted with these imaging features to identify correctly the prior RF ablation and to look carefully for underlying tumor in the treatment bed. This renal halo is often confused with residual/recurrent tumor or angiomyolipoma. Cary Siegel, M.D.
IMAGING
Imaging CA9 Level in Renal Cyst Fluid: A Possible Molecular Diagnosis of Malignant Tumours G. Li, G. Feng, M. Cuilleron, A. Zhao, A. Gentil-Perret, M. Cottier, C. Genin and J. Tostain Department of Urology, North Hospital, CHU of Saint-Etienne, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France Histopathology 2009; 54: 880 – 884.
Aims: The preoperative differentiation of malignant renal cystic tumours from benign lesions is critical, and it remains a common diagnostic problem. The aim was to examine if the Carbonic anhydrase 9 (CA9) level in cyst fluid can provide a molecular diagnosis of malignant cyst. Methods and Results: Twenty-eight patients with a cystic renal mass were included. Fine-needle aspiration was performed to obtain the fluid. Postoperative pathology confirmed that there were 16 cystic renal cell carcinomas. Twelve benign cystic tumours were used as controls. One hundred microlitres of supernatant of cyst fluid was used to measure the CA9 protein level, which was measured by an enzyme-linked immunosorbent assay technique. CA9 was strongly detected and considered as positive in the cyst fluid of all 16 cystic malignant tumours (⬎1000 pg/ml), whereas its expression was negative in 11/12 benign cystic tumours (⬍300 pg/ml). The difference in percentages of positive CA9 between malignant and benign renal cystic tumours was significant (P ⬍ 0.001). Conclusion: The fluid of malignant cystic renal tumours contains a high level of CA9 protein. The measurement of CA9 level in cyst fluid may be used as a molecular diagnosis for differentiation between malignant and benign renal cystic masses. Editorial Comment: Cystic renal lesions are common. However, differentiating benign renal cysts from malignant cysts is difficult. Often radiologists are reluctant to aspirate renal cysts because 1) the cyst aspirate results may be misleading and 2) post-aspiration followup imaging will be confounded by the intervening procedure. These authors explore using CA9 level as a specific marker for cystic renal cell carcinoma. A total of 28 cystic renal tumors were studied—16 cystic renal cell carcinomas and 12 benign cystic tumors that were used as controls. The authors theorize that pathological changes in the cyst wall may alter the composition of cyst fluid. Malignant renal cyst fluid will contain tumor proteins shed from the tumor cells. Since solid clear cell carcinomas and the majority of papillary carcinomas are CA9 positive, perhaps they will shed these markers in the cystic fluid. Using computerized tomographic guidance, an 18 gauge needle was placed in the cystic mass and fluid was aspirated. The volume of fluid varied from 1 to 80 ml. In this series all of the cystic renal cell carcinomas were CA9 positive. Of the 12 benign cysts 11 had absence or a low level of CA9. The study produced a sensitivity of 100% and a specificity of 92%. These authors note that the CA9 ELISA kit is now commercially available. I suspect that this CA9 information will be extremely helpful, and when assessed in conjunction with the cytology of the cyst fluid and the radiology features of the cyst it will improve our diagnostic accuracy. Cary Siegel, M.D.
IMAGING
1775
Kidney Neoplasms: Renal Halo Sign After Percutaneous Radiofrequency Ablation—Incidence and Clinical Importance in 101 Consecutive Patients T. C. Schirmang, W. W. Mayo-Smith, D. E. Dupuy, M. D. Beland and D. J. Grand Department of Diagnostic Imaging, Rhode Island Hospital and Warren Alpert Medical School of Brown University, Providence, Rhode Island Radiology 2009; 253: 263–269.
Purpose: To describe the incidence and clinical importance of the renal halo sign after percutaneous radiofrequency ablation (RFA) of renal neoplasms. Materials and Methods: Institutional review board approval was obtained for this HIPAA-compliant retrospective study. The study population consisted of 101 consecutive patients with 106 solid renal neoplasms that were treated with percutaneous RFA. Postablation computed tomographic (CT) and magnetic resonance (MR) images were retrospectively reviewed by three board-certified radiologists to determine the presence of the renal halo sign. Statistical analyses were performed to determine reader agreement and assess the effect that tumor size and location, radiofrequency (RF) applicator type, RFA treatment time and success, maximum RFA treatment temperature, and number of RF applications performed had on development of the renal halo sign. Results: The renal halo sign developed in 79 (75%) of the 106 ablated tumors. Average imaging follow-up lasted 25 months (range, 1–98 months). The renal halo sign appeared, on average, 6 months (range, 1 month to 3 years) after RFA. The renal halo sign resolved in five (6%) of 79 tumors treated. Interobserver agreement for the presence of the renal halo sign was high. Tumor size and location, RF applicator type, RFA treatment time and success, maximum RFA treatment temperature, and number of RF applications performed were not independent predictors of renal halo sign development. Conclusion: The renal halo sign is seen in 75% of patients after percutaneous RFA of renal neoplasms. It may decrease in size over time; however, it rarely disappears. It is important to recognize this sign, as it can be mistaken for recurrent tumor or angiomyolipoma by radiologists who are not familiar with RFA. Editorial Comment: Image guided tumor ablation is becoming more popular for treatment of patients with renal neoplasms. Understanding the postoperative appearance in patients who have undergone either RF ablation or cryoablation is essential for the radiologist, since some of the postoperative appearances can initially seem peculiar and be misinterpreted as residual or recurrent disease. The renal halo sign is one of these features commonly seen in patients who have undergone RF ablation. The authors describe the renal halo sign as a rim of macroscopic fat that surrounds at least 50% of the treated tumor. The fat is then surrounded by a thin rim of fibrosis. The halo is typically thin and defines the margin from the ablated tumor bed and the surrounding perinephric fat. The renal halo sign can be seen on CT and MR imaging. The renal halo encompasses a centrally treated tumor (which, if treated effectively, will not enhance on post-contrast studies), and is typically bright on T1-weighted images and dark on T2-weighted images. The authors found no correlation between the presence of the renal halo sign and the original tumor size. Urologists and radiologists should become acquainted with these imaging features to identify correctly the prior RF ablation and to look carefully for underlying tumor in the treatment bed. This renal halo is often confused with residual/recurrent tumor or angiomyolipoma. Cary Siegel, M.D.