Oncocytoma: Benign Tumor of the Kidney
Definition of Oncocytoma
Oncocytoma is a benign kidney tumor.
Epidemiology
3–7% of all kidney tumors.
Pathology of Oncocytoma
Gross pathology:
Homogeneous brown kidney tumor, often with a central scar.
Microscopic pathology:
Oncocytoma is characterized by polygonal eosinophilic cells arranged in clusters. The cells are rich in mitochondria, the cell nuclei are in part pleomorphic. The assignment of tumors with nuclear atypia to oncocytoma or renal cell carcinoma is controversial.
Diagnostic Work-Up of Oncocytoma
A preoperative distinction between oncocytoma and renal cell carcinoma is not possible, most authors recommend partial nephrectomy and microscopic examination of the tumor.
Ultrasound of Oncocytoma:
With ultrasound imaging, an oncocytoma is indistinguishable from a renal cell carcinoma [fig. ultrasound imaging].Computed Tomography:
Oncocytomas present as contrast media enriching renal tumors with 4–6 cm in size. A central star-shaped scar is often visible, but the differential diagnosis to renal cell carcinoma is difficult (Choudhary et al, 2009).
MRI:
Oncocytomas present like in CT with a clearly visible capsule and a central stellate scar.
Renal Biopsy:
Renal biopsy is possible, but it is difficult to distinguish oncocytomas from renal cell cancer (e.g. eosinophilic variants) and to exclude the coexistence of RCC and oncocytomas.
Treatment of Renal Oncocytoma
Surgical exposure [fig. intraoperative finding of an oncocytoma]. If an oncocytoma is suspected, an organ-preserving approach (partial nephrectomy) should be pursued.
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References
- Choudhary, S.; Rajesh, A.; Mayer, N. J.; Mulcahy, K. A. & Haroon, A.
- Renal oncocytoma: CT features cannot reliably distinguish oncocytoma from other
renal neoplasms.
Clin Radiol, 2009, 64, 517-522
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Dr. med. Dirk Manski
man...@urologielehrbuch.de