Histopathologic features and parameters predicting recurrence potential of small renal masses.

Abstract

Background: Small renal masses (SRMs) are defined as contrast-enhanced masses with a diameter of ≤4 cm, usually consistent with clinical stage T1a renal cell carcinoma (RCC). This study aimed to explore the histopathological features of a contemporary series of SRMs and investigate parameters that could predict their pathological nature, metastatic potential, and recurrence potential.

Materials and methods: Small renal masses were identified in 166 of 427 patients who underwent surgery for suspected RCC. The radical nephrectomy/partial nephrectomy ratio was 1:44, and autotransplantation was performed in a single case. Variables associated with metastatic recurrence of SRM were analyzed using χ² and logistic regression models.

Results: Renal cell carcinoma was confirmed in 86% (n = 143) of cases, whereas benign tumors were present in 14% (n = 23) of cases. Seventeen percent of the RCC cases were high-grade (Fuhrman G3-4). Among SRMs with a diameter of >2 cm, 71% were malignant. The mean ± standard deviation diameter of the removed SRMs was 28 ± 12 mm, significantly higher in the malignant SRMs group (31 ± 8 vs. 24 ± 9 mm) (p = 0.005). During follow-up, local recurrence was identified in 4 patients versus new distant metastasis in 11 patients. Metastatic lesions were detected in the lungs (1.8%), bone (1.2%), distant (1.9%) and regional lymph nodes (1.2%), liver (0.6%), and multiple organs (2.4%). Patients with malignant SRMs were significantly older than those with benign tumors (p = 0.036). The multivariate analysis identified tumor size, Fuhrman grade, stage, nodal and distant metastasis status, tumor localization, and treatment modality as characteristics significant for tumor recurrence.

Conclusions: The majority of treated neoplasms were malignant, but their incidence was low among SRMs with a diameter of <2 cm. Our results emphasized the importance of histopathological features and treatment modalities in predicting malignant recurrence.