Metastatic Patterns and Adverse Histopathologic Features in Advanced Renal Cell Carcinoma: A Five-Year Single-Center Retrospective Pathology Study

Background and Objectives: Renal cell carcinoma (RCC) exhibits heterogeneous and sometimes unpredictable metastatic behavior, involving both common and uncommon anatomic sites. Institutional analyses of histopathologically confirmed metastatic RCC may improve diagnostic recognition and clinical awareness. This study aimed to characterize the metastatic distribution and histopathologic features of RCC diagnosed in a single tertiary center over a five-year period. Materials and Methods: A retrospective review of the pathology database of the Department of Pathology, “Pius Brînzeu” Emergency County Hospital, Timișoara, was performed to identify all histologically confirmed cases of metastatic RCC diagnosed between January 2020 and December 2024. Case identification was based on pathology reports of metastatic lesions. In a subset of cases, corresponding pathology reports of the primary renal tumor were available and reviewed. Histopathological data collected included WHO/ISUP grade, tumor necrosis, sarcomatoid and/or rhabdoid differentiation, vascular invasion, surgical margin status, tumor size, and pathological T stage (pT). Exploratory analyses were performed to assess associations between metastatic site and selected histopathological features. Results: Thirty-two cases of metastatic RCC were identified, all demonstrating clear cell morphology. The mean patient age was 62.9 years, with a marked male predominance. Among cases with available primary tumor data, high WHO/ISUP grade and adverse histopathologic features were frequently observed. The most common metastatic sites in our institution were the brain and bone, followed by the adrenal gland, lymph nodes, and liver. Less frequent metastatic involvement included the pancreas, testis, vagina, skin, and peritoneum. Exploratory analyses did not demonstrate statistically significant associations between metastatic site and tumor grade, necrosis, or sarcomatoid/rhabdoid differentiation; however, descriptive trends were observed, including the association of brain metastases with high-grade tumors and the high prevalence of tumor necrosis across metastatic sites. Conclusions: This pathology-based retrospective series highlights the broad metastatic spectrum of RCC, including both typical and rare anatomic sites. The predominance of clear cell morphology and the frequent association with adverse histopathologic features support the link between aggressive tumor biology and metastatic disease. Although no statistically significant associations were identified, the observed patterns suggest potential relationships between metastatic distribution and tumor characteristics, warranting further investigation in larger studies.