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Abstract and Introduction
Abstract
We studied the pathologic features and whether clinical features could predict pathologic outcomes in small renal masses. The study included all adult patients with solitary, nonmetastatic renal masses 4 cm or smaller confirmed by nephrectomy or needle biopsy between 2004 and 2006. Tumor size, histologic type, Fuhrman nuclear grade, and stage were obtained from surgical pathology reports. Clinical variables included age, sex, tumor size, and symptomatology.
The study included 290 men and 198 women (mean age, 59.3 years). Median tumor size was 2.6 cm (range, 0.5-4.0 cm). Approximately 84% of masses were incidentally detected. Nonneoplastic entities, benign neoplasms, and low- and high-grade carcinoma accounted for 1.6%, 18.0%, 49.0%, and 31.4% of masses, respectively. Women were more likely to have a benign mass (27.3% vs 14.5% of men, P < .001). Age (P = .56), tumor size (mean, 2.63 vs 2.46 cm for benign; P = .08), and symptomatology (P = .46) were not associated with malignancy. Multivariate analyses using sex, age, tumor size, and symptomatology failed to produce a model useful to predict the pathology of individual tumors. This inability may argue for an increased role for needle biopsy in their evaluation.
Introduction
During the past few decades, there has been an increase in the incidence of small renal masses, owing in part to the increased use of abdominal cross-sectional imaging in a workup for an unrelated condition.[1-3] Although the majority of small renal masses represent renal cell carcinoma (RCC), a significant proportion is ultimately found to be benign or nonneoplastic on histopathologic examination. In a large 30-year retrospective study, Frank et al[4] found that 221 (23.3%) of 947 renal masses measuring less than 4 cm were benign. More recently, Snyder et al[5] found that 98 (18.5%) of 531 renal masses measuring 4 cm or less were benign. In addition, most small RCCs are low-grade. In the series by Frank et al,[4] 81.3% of RCCs measuring less than 5 cm had low-grade histologic features.
Several small, prospective studies examining outcomes of expectant management provide insight into the natural history of small renal masses. Kassouf et al[6] studied a cohort of 24 patients with small renal masses (mean, 3.3 cm). At a mean follow-up of 31 months, only 5 (21%) showed tumor growth, and there were no cases of metastasis.[6] Kouba et al,[7] in a study of 43 patients with a mean tumor size of 2.9 cm, showed tumor growth in 74% of patients (mean, 0.7 cm/y) but no cases of metastasis at a mean follow-up of 3 years.
Therefore, there has been a paradigm shift in the management of these small masses, with partial nephrectomy and minimally invasive ablative therapies gaining increased acceptance. Active surveillance with serial imaging studies has been used as an alternative to surgery, mainly in patients with underlying comorbidities.
Several studies have examined the relationship between tumor size and pathologic diagnosis, but few have examined the influence of additional clinical variables, including age, sex, and symptomatology. In addition, there is little information regarding pathologic features of T1a tumors, which are more likely to be managed conservatively. Knowledge of the pathologic nature of these small renal masses will help clinicians and patients to choose the appropriate treatment modality.
The objectives of this study were to describe the pathologic features of a contemporary series of solitary renal masses measuring 4 cm or less and to determine whether sex, age, tumor size, and/or symptomatic manifestations could predict the pathologic nature of such masses.
Materials and Methods
The Cleveland Clinic (Cleveland, OH) surgical pathology database was searched for nephrectomies (partial and radical) and renal mass biopsies during the 2-year period between July 2004 and July 2006. Cases of resections for upper tract urothelial neoplasms, retroperitoneal sarcomas, and end-stage renal disease were excluded. In addition, the data for patients with recurrent RCC or a documented history of von Hippel-Lindau syndrome were excluded. Only the data for adult patients with solitary, nonmetastatic renal masses 4 cm or smaller confirmed by nephrectomy or needle biopsy were included in the study. Pathologic data, including tumor size, histologic type, Fuhrman nuclear grade, and stage were obtained from surgical pathology reports.
All diagnoses were made by genitourinary pathologists using the 2004 World Health Organization classification of renal neoplasms. In cases with a needle biopsy–proven diagnosis followed by ablative therapy rather than resection, the tumor size was obtained from preoperative computed tomography scans. A low-grade neoplasm was defined as an organ-confined tumor (2002 American Joint Committee on Cancer stage T1a) with a Fuhrman nuclear grade of 1 or 2 without lymphatic or vascular invasion, tumor necrosis, or sarcomatoid differentiation. Hybrid oncocytic tumors with features of renal oncocytoma and chromophobe RCC and carcinoid tumor were also classified as low-grade neoplasms. Tumors with any of the following characteristics were categorized as high-grade neoplasms: American Joint Committee on Cancer stage T3, lymph node involvement, microscopic or macroscopic vascular invasion, Fuhrman nuclear grade 3 or 4, or a sarcomatous component.
Age, sex, and clinical manifestations were recorded. The clinical manifestations were categorized as symptomatic (flank pain, hematuria, or symptoms of metastatic disease) or asymptomatic. Descriptive statistics were obtained for continuous and categorical variables. Associations were analyzed depending on the nature of the variables involved (ie, t test, χ2 test, logistic regression). Multivariate logistic regression was used to construct a model to predict the pathologic classification of individual tumors based on the clinical parameters. JMP 7.0 (2007, SAS Institute, Cary, NC) was used to analyze the data. The Cleveland Clinic Institutional Review Board approved the study.
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