A multi-institutional study on histopathological characteristics of surgically treated renal tumors: the importance of tumor size

Rate of benign histology after resection of suspected renal cell carcinoma: multicenter comparison between Korea and the United States

BACKGROUND

In the United States, the rate of benign histology among resected renal tumors suspected to be malignant is increasing. We evaluated the rates in the Republic of Korea and assessed the racial effect using recent multi-institutional Korean-United States data.

METHODS

We conducted a multi-institutional retrospective study of 11,529 patients (8,812 from The Republic of Korea and 2,717 from the United States) and compared the rates of benign histology between the two countries. To evaluate the racial effect, we divided the patients into Korean, Asian in the US, and Non-Asian in the US.

RESULTS

The rates of benign histology and small renal masses in Korean patients were significantly lower than that in United States patients (6.3% vs. 14.3%, p < 0.001) and (≤ 4 cm, 7.6% vs. 19.5%, p < 0.001), respectively. Women, incidentaloma, partial nephrectomy, minimally invasive surgery, and recent surgery were associated with a higher rate of benign histology than others.

CONCLUSIONS

In Korea, the rate of benign histology among resected renal tumors was significantly lower than that in the United States. This disparity could be caused by environmental or cultural differences rather than racial differences. Our findings suggest that re-evaluating current context-specific standards of care is necessary to avoid overtreatment.

Preoperatively misclassified, surgically removed benign renal masses: a systematic review of surgical series and United States population level burden estimate

PURPOSE

A significant proportion of renal masses removed for suspected malignancy are histologically benign with the probability inversely proportional to lesion size. To our knowledge the number of preoperatively misclassified benign renal masses treated with nephrectomy is currently unknown. Given the increasing incidence and decreasing average size of renal cell carcinoma, this burden is likely increasing. We estimated the population level burden of surgically removed, preoperatively misclassified benign renal masses in the United States.

MATERIALS AND METHODS

We systematically reviewed the literature for studies of pathological findings of renal masses removed for suspected renal cell carcinoma based on preoperative imaging through July 1, 2014. We excluded studies that did not describe benign pathology and with masses not stratified by size, and in which pathology results were based on biopsy. SEER data were queried for the incidence of surgically removed renal cell carcinomas in 2000 to 2009.

RESULTS

A total of 19 studies of tumor pathology based on size met criteria for review. Pooled estimates of the proportion of benign histology in our primary analysis (American studies only and 1 cm increments) were 40.4%, 20.9%, 19.6%, 17.2%, 9.2% and 6.4% for tumors less than 1, 1 to less than 2, 2 to less than 3, 3 to less than 4, 4 to 7 and greater than 7, respectively. The estimated number of surgically resected benign renal masses in the United States from 2000 to 2009 increased by 82% from 3,098 to 5,624.

CONCLUSIONS

These estimates suggest that the population level burden of preoperatively misclassified benign renal masses is substantial and increasing rapidly, paralleling increases in surgically resected small renal cell carcinoma. This study illustrates an important and to our knowledge previously unstudied dimension of overtreatment that is not directly quantified in contemporary surveillance data.

A review of contemporary data on surgically resected renal masses--benign or malignant?

OBJECTIVE

To clearly define the proportions of benign vs malignant histologic findings in resected renal masses through an in-depth review of the contemporary medical data to assist in preoperative risk assessment.

MATERIALS AND METHODS

PubMed and select oncology congresses were searched for publications that identify the histologic classification of resected renal masses in a representative sample from the contemporary data: [search] incidence AND (renal cell carcinoma AND benign); incidence AND (renal tumor AND benign); percentage AND (renal cell carcinoma AND benign); limit 2003-2011.

RESULTS

We identified 26 representative studies meeting the inclusion criteria and incorporating 27,272 patients. The frequency of benign tumors ranged from 7% to 33%, with most studies within a few percentage points of the mean (14.5% ± 5.2%, median 13.9%). Clear cell renal cell carcinoma occurred in 46% to 83% of patients, with a mean of 68.3% (median 61.3; SD = 11.9%). An inverse relationship between tumor size and benign pathologic features was identified in 14 of 19 (74%) studies that examined an association between tumor size and pathologic characteristics. A statistically significant correlation between clear cell renal cell carcinoma and tumor size was identified in 13 of 19 studies (63%). The accuracy of preoperative cross-sectional imaging was low in the 2 studies examining computed tomography (17%).

CONCLUSION

Benign renal tumors represent ∼15% of detected surgically resected renal masses and are more prevalent among small clinical T1a lesions. Noninvasive preoperative differentiation between more and less aggressive renal masses would be an important clinical advance that could allow clinicians greater diagnostic confidence and guide patient management through improved risk stratification.

Incidence and predictive factors of benign renal lesions in Korean patients with preoperative imaging diagnoses of renal cell carcinoma

The present study was performed to determine the incidence and predictive factors of benign renal lesions in Korean patients undergoing nephrectomy for presumed renal cell carcinoma on preoperative imaging. We analyzed the pathologic reports and medical records of 1,598 eligible patients with unilateral, nonmetastatic, and nonfamilial renal masses. Of the 1,598 renal masses, 114 (7.1%) were benign lesions, including angiomyolipoma in 47 (2.9%), oncocytoma in 23 (1.4%), and complicated cysts in 18 (1.1%) patients. On univariate analysis, the proportion of benign lesions was significantly higher in female patients, and in patients with smaller tumors, cystic renal masses, and without gross hematuria as a presenting symptom. When renal lesions were stratified by tumor size, the proportion of benign as opposed to malignant lesions decreased significantly as tumor size increased. On multivariate analysis, female gender, smaller tumor size, and cystic lesions were significantly associated with benign histological features. The findings in this large cohort of Korean patients show a lower incidence (7.1%) of benign renal lesions than those of previous Western reports. Female gender, cystic renal lesions, and smaller tumor size are independent predictors of benign histological features.

Trends of presentation and clinical outcome of treated renal angiomyolipoma

PURPOSE

The purpose of this study is to set guidelines for the management of renal angiomyolipoma (AML), clinical prognosis according to tumor size, in association with tuberous sclerosis complex (TSC), multiplicity, radiographic finding, and treatment modality.

MATERIALS AND METHODS

Between March 1998 and October 2008, 129 out of 254 patients with AML who underwent surgical intervention or angioembolization were enrolled. Diagnosis of AML was determined by the presence of a low attenuated component on CT imaging or by pathological confirmation. Indications of treatment were intractable pain, hematuria, suspicion of malignancy, large tumor size, spontaneous rupture, and radiographically equivocal tumors in which a differential diagnosis was needed to rule out malignancy. Parameters including age, sex, tumor size, multiplicity, radiographic characteristics, association with TSC, and treatment modality were reviewed.

RESULTS

Age at presentation was 50.6 years and mean tumor size was 3.5 cm. Presentation symptoms were flank pain, hematuria, spontaneous rupture, and fatigue. 97 (75.2%) patients were incidentally discovered. 100 (77.5%) were females. 68 (52.7%) underwent nephron-sparing surgery (NSS), 35 (27.1%) radical nephrectomy, and 26 (20.2%) angioembolization. TSC was accompanied in 12 (9.3%) patients. No patient developed renal function impairment during the mean follow-up period of 64.8 months. Patients with TSC presented at a younger age, along with larger, bilateral, and multiple lesions.

CONCLUSION

Significant differences in clinical manifestations and treatment outcomes were noted in respect to tumor characteristics, association with TSC, and treatment modality. Considering the benign nature of AML, these parameters ought to be considered when deciding upon active surveillance or prophylactic intervention.