Oncocytoma is a benign renal cell tumor with mainly solid-nested architecture composed of predominantly large eosinophilic cells packed with mitochondria.
Oncocytomas are sporadic tumors; cases in association with Birt-Hogg-Dubé (an autosomal dominant disease associated with mutation of the folliculin gene) have been reported.
They comprise 5% of adult renal epithelial tumors in surgical series.
The peak incidence is in the seventh decade of life.
Its male-to-female ratio is 2:1.
There is no prevalence of site.
Partial or radical nephrectomy, based on the tumor size, is the standard. In selected cases, active surveillance may be an option.
Renal oncocytomas are benign neoplasms.
Tumor is a well-circumscribed uniform mahogany brown color mass; when large it frequently displays a stellate central scar. Foci of hemorrhage can be observed, but necrosis is constantly absent. They are usually solitary, but could be multifocal and/or bilateral.
Oncocytoma shows a compact solid or nesting arrangement of large cells in an edematous and hyalinized stroma. Neoplastic cells have abundant granular eosinophilic cytoplasm (Fig. 1), reflecting the presence of numerous mitochondria visible at the ultrastructural analysis. The nuclei of renal oncocytoma cells are regular, round with a nucleolus often evident. Rarely, occasional degenerative bizarre nuclei or scattered nests of small cells, so-called oncoblast, can be observed. A tubulocystic pattern of growth may be prevalent in a few cases. The extension of oncocytoma cells into perirenal adipose tissue can occur in rare cases.
Immunohistochemical profile of oncocytomas is characterized by vimentin and CK7 negativity in contrast with the expression of CD117, S-100A1, and parvalbumin. Staining for CD10 may be observed, whereas CD13 is constantly negative.
Oncocytomas are usually characterized by normal karyotype; monosomy of chromosomes 1 and 14, often with Y chromosome loss, and structural abnormalities of 11q13 can be observed.
References and Further Reading
- Brunelli, M., Delahunt, B., Gobbo, S., Tardanico, R., Eccher, A., Bersani, S., Cossu-Rocca, P., Parolini, C., Balzarini, P., Menestrina, F., Cheng, L., Eble, J. N., & Martignoni, G. (2010). Diagnostic usefulness of fluorescent cytogenetics in differentiating chromophobe renal cell carcinoma from renal oncocytoma: A validation study combining metaphase and interphase analyses. American Journal of Clinical Pathology, 133(1), 116–126.CrossRefGoogle Scholar
- Rocca, P. C., Brunelli, M., Gobbo, S., Eccher, A., Bragantini, E., Mina, M. M., Ficarra, V., Zattoni, F., Zamò, A., Pea, M., Scarpa, A., Chilosi, M., Menestrina, F., Bonetti, F., Eble, J. N., & Martignoni, G. (2007). Diagnostic utility of S100A1 expression in renal cell neoplasms: An immunohistochemical and quantitative RT-PCR study. Modern Pathology, 20(7), 722–728.CrossRefGoogle Scholar