Histopathologic features and parameters predicting recurrence potential of small renal masses

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.

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.

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.

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.