Background

Primary renal mesenchymal neoplasms are rare non-epithelial tumors of the kidney exhibiting diverse histopathological patterns and variable biological behavior. Owing to their rarity and overlapping clinicoradiological features, accurate diagnosis remains challenging. The present study was conducted to evaluate the clinicopathological spectrum, radiological features, immunohistochemical profile, and predictors of malignancy among adult patients with primary renal mesenchymal neoplasms.

Methods

This hospital-based cross-sectional study included 564 adult patients diagnosed with primary renal mesenchymal neoplasms at a tertiary care center. Demographic, clinical, radiological, histopathological, and immunohistochemical data were analyzed. Tumors were classified according to standard histopathological criteria and immunohistochemical findings. Comparative analysis between benign and malignant tumors was performed using appropriate statistical tests, and multivariate logistic regression analysis was used to identify predictors of malignancy.

Results

The mean age of patients was 48.7 ± 13.6 years, with male predominance (58.2%). Flank pain was the most common presenting symptom (66.0%). Angiomyolipoma was the commonest tumor subtype (50.7%), while leiomyosarcoma was the predominant malignant neoplasm (12.8%). Malignant tumors occurred in significantly older patients and were associated with larger tumor size, hematuria, necrosis, vascular invasion, and perinephric fat involvement (p<0.001). Tumor size >7 cm (OR=4.96), necrosis on imaging (OR=5.62), and vascular invasion (OR=6.18) emerged as significant independent predictors of malignancy. Immunohistochemistry aided accurate differentiation among spindle-cell renal tumors.

Conclusion

Primary renal mesenchymal neoplasms demonstrate a broad clinicopathological and immunohistochemical spectrum. Larger tumor size, hematuria, necrosis, and vascular invasion were strongly associated with malignant behavior. Integrated clinicoradiological, histopathological, and immunohistochemical evaluation is essential for accurate diagnosis and prognostic assessment of these rare renal tumors.