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Imaging spectrum of renal oncocytomas: a pictorial review with pathologic correlation
Kousei Ishigami
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Aaron R. Jones
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Laila Dahmoush
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Leandro V. Leite
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Marius G. Pakalniskis
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Thomas J. Barloon
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L. Dahmoush Department of Pathology, University of Iowa Hospitals and Clinics
,
Iowa City, IA
,
USA
Objectives The purpose of this pictorial review is to present the imaging spectrum of renal oncocytomas with radiologicalpathological correlation. Conclusion The differences in tumour cellularity (high cellularity or low cellularity with abundant stroma) and haemorrhagic/cystic change contribute to a wide spectrum of imaging findings of renal oncocytomas. Imaging findings substantially overlap those of common subtypes of clear cell and non-clear cell renal cell carcinomas. Multifocal renal oncocytomas are not rare, and making the diagnosis of oncocytoma with concomitant renal cell carcinoma is difficult. In addition, renal oncocytomas that demonstrate interval growth or develop in the setting of end-stage renal disease may be mistaken for malignancy. Teaching Points High cellular components demonstrate avid arterial enhancement and subsequent washout. Low cellular components demonstrate gradual subsequent enhancement owing to abundant stroma. Cystic and hemorrhagic changes may account for lesion heterogeneity in the delayed phase. Multifocal oncocytomas and oncocytomas coexisting with renal cell carcinoma are not rare. Renal oncocytomas may demonstrate interval growth.
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Renal oncocytoma is a benign renal tumour, accounting for
approximately 37 % of all renal tumours [1]. Typical
imaging findings of renal oncocytoma are described as a
homogeneous hypervascular mass with subsequent washout in the
delayed phase [2, 3] (Fig. 1). A central scar is a characteristic
finding, especially in a large oncocytoma [4]. However, such
classic imaging findings are not common [5]. In many cases,
renal oncocytomas are surgically resected because
preoperative imaging diagnosis is not reliable to distinguish
oncocytoma from renal cell carcinoma (RCC).
Kim et al. [6] found that segmental enhancement inversion
based on the corticomedullary and early excretory phase was a
characteristic enhancement pattern of oncocytoma (Fig. 2).
Segmental enhancement inversion is a term defined as a renal
lesion that has two distinct zones of enhancement which show
inverse patterns between the corticomedullary (3040 s) and
early excretory (120180 s) phases. One zone is
hyperenhancing on the corticomedullary phase, which subsequently
becomes hypo-enhancing on the early excretory phase. The
other zone is hypo-enhancing on the corticomedullary phase
and becomes hyper-enhancing on the early excretory phase
[6, 7]. However, other studies have found it controversial
whether or not segmental enhancement inversion is
characteristic for oncocytoma [710]. Additionally, several studies
examining the discrimination of RCC from oncocytoma based
on the corticomedullary phase have shown inconsistent results
[2, 1113].
Therefore, renal oncocytomas demonstrate various
imaging findings. Not only may the discrimination of oncocytoma
from RCC be challenging, but also the presence of
Fig. 1 A 71-year-old man with classic renal oncocytoma in the left
kidney. a The corticomedullary phase of the axial T1-weighted gradient
echo (GRE) magnetic resonance (MR) image with fat saturation
demonstrates an arterially enhancing mass (arrow) with hypointense
central scar (small arrow). b The nephrographic phase demonstrates
washout with enhancing central scar. c The axial T2-weighted fast spin
echo (FSE) image with fat saturation shows the tumour to be of moderate
signal (arrow) with hyperintense central scar (small arrow). d (High
magnification) Oncocytoma, organoid pattern, tightly packed nests of
tumour cells (T) with visible capillaries in the stroma (arrow)
oncocytoma with concurrent RCC may be a diagnostic
problem. Although imaging findings may not reliably discriminate
oncocytoma from RCC, it is meaningful for radiologists to
understand the wide imaging spectrum of oncocytomas when
approaching the differential diagnosis of renal tumours.
The purpose of this pictorial review is to present the
imaging spectrum of renal oncocytomas. To aid in understanding
the imaging findings of oncocytomas,
radiologicalpathological correlations are provided.
The diagnostic difficulties of discriminating renal
oncocytoma from renal cell carcinoma
Several studies examining the discrimination of clear cell
RCC from oncocytoma based on arterial enhancement have
revealed inconsistent results. For example, Gakis et al. [2] and
Bird et al. [11] described that oncocytomas demonstrated
g r e a t e r e n h a n c e m e n t t h a n c l e a r c e l l R C C i n t h e
corticomedullary phase. On the other hand, Young et al. [12]
described that clear cell RCC demonstrated greater
enhancement than oncocytoma. Pierorazio et al. [13] described that
peak enhancement of clear cell RCC was seen predominantly
in the corticomedullary phase, while that of oncocytoma was
seen predominantly in the (...truncated)