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Renal oncocytoma: sonographic analysis of 14 cases
Abstract:
The sonographic features of 15 histologically confirmed renal oncocytomas in 14 patients are presented. Lesions were evaluated for homogeneity, echogenicity, margination, venous invasion, and nodal enlargement. Nine were less than 5.5 cm in diameter, homogeneous, and well circumscribed. Three lesions were greater than 8 cm in diameter, contained areas of central necrosis or calcification, and were nonspecific for renal oncocytoma. One of these lesions (12 cm) contained a central scar. Two masses were slightly inhomogeneous and, at best, moderately circumscribed. In no case were metastatic nodes or venous invasion present. Since about 6% of renal cell carcinomas may have this appearance, the homogeneous, well marginated renal mass that is isoechoic with cortex and less than 5.5 cm in diameter is as likely to represent renal cell carcinoma as it is an oncocytoma. Although only present in one of the cases, the central fibrotic scar in a larger mass has been described in oncocytoma and may be the most specific feature. Preoperative investigation with fine-needle aspiration biopsy for cytology may be indicated in an attempt to avoid radical nephrectomy in selected patients.
Insights
Renal oncocytomas often appear homogeneous and well-defined on ultrasound, especially when smaller than 5.5 cm. Larger masses with central necrosis or scars may be less specific, necessitating further investigation.
Area of Science:
- Radiology
- Urologic Oncology
- Diagnostic Imaging
Background:
- Renal oncocytomas are benign kidney tumors.
- Accurate preoperative diagnosis can prevent unnecessary surgeries.
Purpose of the Study:
- To describe the sonographic features of renal oncocytomas.
- To differentiate oncocytomas from renal cell carcinomas based on imaging characteristics.
Main Methods:
- Retrospective review of 15 histologically confirmed renal oncocytomas in 14 patients.
- Evaluation of sonographic features including homogeneity, echogenicity, margination, venous invasion, and nodal enlargement.
Main Results:
- Nine tumors (<5.5 cm) were homogeneous and well-circumscribed.
- Three larger tumors (>8 cm) showed central necrosis/calcification; one had a central scar.
- No venous invasion or nodal metastasis was observed.
- Small, homogeneous, isoechoic masses (<5.5 cm) are difficult to distinguish from renal cell carcinoma.
Conclusions:
- Sonographic features of renal oncocytomas vary with size and presence of necrosis or scars.
- A central fibrotic scar may be a specific feature of oncocytoma.
- Fine-needle aspiration biopsy may aid in preoperative diagnosis to avoid radical nephrectomy.