Abstract
Renal oncocytoma represents the most common type of benign neoplasm that is an increasing concern for urologists, oncologists, and nephrologists due to its difficult differential diagnosis and frequent overtreatment. It displays a variable neoplastic parenchymal and stromal architecture, and the defining cellular element is a large polygonal, granular, eosinophilic, mitochondria-rich cell known as an oncocyte. The real challenge in the oncocytoma treatment algorithm is related to the misdiagnosis due to its resemblance, at an initial radiological assessment, to malignant renal cancers with a completely different prognosis and medical treatment. Unfortunately, percutaneous renal biopsy is not frequently performed due to the possible side effects related to the procedure. Therefore, the majority of oncocytoma are diagnosed after the surgical operation via partial or radical nephrectomy. For this reason, new reliable strategies to solve this issue are needed. In our review, we will discuss the clinical implications of renal oncocytoma in daily clinical practice with a particular focus on the medical diagnosis and treatment and on the potential of novel promising molecular biomarkers such as circulating microRNAs to distinguish between a benign and a malignant lesion.
Highlights
Renal oncocytoma (RO) is a benign renal neoplasm that is an increasing concern for urologists, oncologists, and nephrologists due to its difficult differential diagnosis from renal cell carcinoma (RCC) and frequent overtreatment
Amin et al reported a morphologic re-examination of 80 cases of oncocytoma, with a non-negligible frequency of abnormal findings: in 42.5% of cases, they observed prominent nucleoli, 50% displayed nuclear pleomorphism and even bizarre cells in 12.5%, while 11% showed perinephric fat infiltration, and 10% had renal parenchymal invasion, which instead would have been expected from a malignant neoplasm such as chromophobe RCC (chRCC) [19]
IHC can be helpful as an additional and integrative tool in the differential diagnosis between oncocytomas and other RCCs, since the former are usually characterized by a 5% of tumor cells [70], sometimes it may display scarce CK7 staining [82], and it will show diffuse, reticular cytoplasmic staining for colloidal iron [84,85], which has led some experts to consider it as the best marker in this differential diagnosis context, it is not formally an IHC marker [82]
Summary
Renal oncocytoma (RO) is a benign renal neoplasm that is an increasing concern for urologists, oncologists, and nephrologists due to its difficult differential diagnosis from renal cell carcinoma (RCC) and frequent overtreatment. It displays a variable neoplastic parenchymal and stromal architecture, and the defining cellular element is a large polygonal, granular, eosinophilic, mitochondria-rich cell known as an oncocyte. A retrospective study from Iceland reported a 0.3/100,000/year age-standardized incidence [8]. It usually presents in adults and older adults with 75% of patients in the 6th–8th decade of life [7], with a reported mean age ranging from 52 to 70.5 years across the literature [11,12]. There is a male predominance, with a M:F ratio ranging from 1.25:1 to 3.3:1 [9,14]
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