458 Primary Renal Mesenchymal Neoplasms: A Retrospective Clinicopathological Study

Abstract

Abstract Aim Mesenchymal tumors are rare primary neoplasms of the kidney with limited demographic data in literature. We sought to study the prevalence of this rare subset of tumors in adults, at our tertiary care hospital focusing on the pathological and radiological characteristics. Method Clinico-radiological and intra-operative details were retrospectively analyzed for adult primary renal mesenchymal neoplasms received between 2006 and 2021 and correlated with the histopathology data. Results Of 2164 nephrectomies performed for neoplastic conditions, 97 (4.5%) were diagnosed as renal mesenchymal tumors. There were 59 (60.8%) benign, 10 (10.3%) with intermediate biologic behavior and 28 (28.9%) malignant tumors. The mean age was similar across these categories. Hematuria was seen in 11 of 38 (29%) intermediate grade and malignant tumors and in only 6 of 59 (10%) benign tumors a difference that was statistically significant (p = 0.017). Tumors ≥ 7cm were more likely to be malignant/intermediate grade than benign (p = 0.027). Classical angiomyolipomas constituted 90% of the benign tumors. Epithelioid angiomyolipomas and solitary fibrous tumors were the common intermediate grade tumors. Undifferentiated small round cell sarcoma was the most common malignant neoplasm. Immunohistochemical and molecular studies were useful for confirmation of diagnosis, particularly in cases of intermediate/malignant tumors. Conclusions Mesenchymal tumors constitute 4.5% of adult primary renal tumors, are predominantly benign tumors but are malignant in 1/4 th of cases. Malignant tumors are typically larger and more often present with hematuria. Immunohistochemistry (IHC) and molecular studies play a role in the diagnosis of intermediate and malignant mesenchymal tumors.