SYNCHRONOUS LIVER METASTASES OF RENAL ONCOCYTOMA: A CASE REPORT AND LITERATURE REVIEW

Introduction/Aim: The 2004 WHO classification of renal tumors in adults described renal oncocytoma (RO) as benign epithelial neoplasia deriving from intercalated cells. The benign nature of this tumor was established in the 1990s. The term “oncocytoma” was initially used to describe lesions in parathyroid glands, thyroid glands and salivary glands. The first case of RO was described by Zippel in 1942. This kind of lesion comprises 3-9% of all renal tumours, with prevalence in male gender. At present, few clinical cases of metastastic metachronous oncocytomas are reported in literature. We describe a patient with synchronous liver mestastases of RO. Case Report: We report a case of a 62-year-old woman affected by left renal mass and 10 liver nodules identified by computed tomography scan. A left radical nephrectomy with excision of 2 of the 10 liver nodules was carried out. Macroscopically, the renal neoplasm extended into the renal pelvis and vascular invasion of minor renal venous branches were reported. By histopathological evaluation, the renal and the hepatic nodules were composed of solid nests of round to polygonal cells with densely granular eosinophilic cytoplasm, round uniform nuclei and scattered nucleoli. An area of oedematous fibrous stroma was present in the central part of the lesions. Neither mitosis nor necrosis could be seen. Renal and hepatic lesions shared the same immunophenotypical profile showing partial positivity for S100A1, CD10 and CD117 and diffuse positivity for PAX-8 and succinate- dehydrogenase. On the contrary, the neoplasms were negative for carbonic anidrase IX, CD13, cytokeratin 7, parvalbumin, vimentin, anti-HEPAT, TTF1, thyroglobulin and HMB45. A fluorescence in situ hibridization (FISH) was suggestive of RO with liver metastasis. Materials and Methods: A research on PubMed was performed with the falling strategy: renal oncocytoma, metastatic renal oncocytoma, renal adult tumours. Discussion: RO is a benign renal tumour, commonly asymptomatic, discovered incidentally with diagnostic imaging. The standard treatment for RO is the surgical excision or radical nephrectomy. More recently, minimally extensive and ablative renal sparing techniques, such as partial nephrectomy, radiofrequency or cryoablation have been alternative options. RO, sometimes, co-exists with a malignant neoplasm that may be present within or adjacent to the oncocytoma; rare cases of metastatic RO have been reported simulating a malignant course. Nevertheless, more than 20 cases with invasive histopathological features are described, 5 of them with distant metastases (liver, skeleton, lungs). Only liver metastases were confirmed at immunohistochemical staining. Review of the literature showed that oncocytomas sharing genetic or molecular features of chromophobe carcinoma may exist, explaining these rare instances of metastases. Conclusion: In the reported case, we provide additional evidence that RO, in extraordinarily rare cases, can have a metastatic potential as it is the only one with a synchronous pathway in the literature. In our case, as well in all the cases previously described, the liver was the organ involved in metastasis, while the presence of metastasis did not seem to affect prognosis.