Keywords
Fuhrman grade - lymphovascular invasion - positron emission tomography - renal cell
carcinoma - synchronous primaries
Introduction
Paired organs such as lungs, breasts, ovaries, and kidneys are always under similar
carcinogenic influence (genetic or environmental). The presence of malignancy in one
increases the chances of synchronous or metachronous primary in others. However, popular
argument against is that it can be metastatic spread from one to others. Bilateral
renal cell carcinoma (RCC) is a rare entity and can present synchronously or asynchronously.
Bilateral RCC can be familial or sporadic. Hereditary RCCs are often bilateral and
occur at younger ages than sporadic tumor. Among the bilateral sporadic renal lesions,
the occurrence of synchronous RCCs is almost equal or can be more than metachronous
lesions. Multiple studies report that the incidence of bilateral RCCs is between 1%
and 5%.[1] Only <2% of patients with RCC can have synchronous sporadic lesions.[2] Pathologically, usually in bilateral RCC, both histological subtypes are concordant,
especially when metachronous; however, discordant subtypes can be present.[3]
Here, we present a case report of a patient with bilateral synchronous RCCs including
surgical, pathological, and metabolic features of renal masses.
Case Report
A 52-year-old male patient with no significant family history of renal malignancies
presented to us with diagnosis of bilateral renal masses. Initially, the patient presented
with hematuria. He was investigated with ultrasound of the abdomen, which revealed
bilateral complex renal masses at the upper pole of the left kidney and lower pole
of the right kidney, respectively. Subsequent contrast-enhanced computed tomography
(CT) scan of the abdomen suggested enhancing exophytic necrotic mass in the left kidney
and large predominantly solid mass in the right kidney. Both masses appeared vascular.
They were categorized as T2a tumors (TNM staging). A suspicious metastatic lesion
was noticed in the liver. Fine-needle aspiration cytology was performed from both
the masses. Cytological findings from the left kidney were positive for atypical cell
while those from the right kidney were inconclusive. The patient was referred for
fluorodeoxyglucose positron emission tomography/CT (FDG PET/CT) scan with intent to
characterize renal masses and liver lesion. Following due consent patient underwent
whole body FDG PET/CT scan as per standard protocols. FDG PET/CT images revealed intense
heterogeneous FDG uptake in the left renal mass while the uptake in the right renal
mass was minimal (isointense with normal renal cortex) [Figure 1]. Maximum standardized uptake value (SUVmax) in the left renal mass was measured 15.5. No FDG uptake was noted in cystic lesions
in the liver and was concluded as benign. A solitary FDG-avid 1.5 cm nodule was seen
in visualized sections of the left lung SUVmax measuring 14.4. No other metastatic lesion was identified in rest of scan.
Figure 1 Fluorodeoxyglucose positron emission tomography-computed tomography scan: Contrast-enhanced
computed tomography images showed enhancing masses in the lower pole of the right
kidney (a, f, i) and upper pole of the left kidney (c, h, i). Fused positron emission
tomography-computed tomography images showed no uptake in the right renal mass (b,
e, j) and peripheral intense fluorodeoxyglucose uptake in the necrotic left renal
mass (d, g, j)
Based on PET/CT finding and clinical evaluation, the patient underwent radical nephrectomy
on the left and partial nephrectomy on the right side. Histopathological analysis
revealed conventional clear cell carcinoma in both kidneys [Figure 2]. Measurement revealed pT1b tumor on the right and pT3a on the left (due to sinus
fat invasion). Perinephric fat and Gerota's fascia were free of tumors. Both tumors
were “Grade III” on Fuhrman grade. On careful evaluation, the only histopathological
difference found between the two masses was lymphovascular invasion (LVI) and necrosis
present in the left renal mass.
Figure 2 Microphotographs of histology of the right (a) and left (b) renal masses. High resolution
images of same; right (c) and left (d). Lymphovascular invasion ([e] arrowheads) and
necrosis ([f] arrow) in the left renal mass, respectively
Discussion
The difference of metabolic activity patterns between primary and presumed metastatic
lesion suggests possibility of two separate disease processes. Here, we observed difference
in metabolic patterns of both renal masses, suggesting that both the lesions though
synchronous are of independent origins. Surprisingly, both the renal masses have almost
identical histology, i.e., conventional clear cell variant. Even the Fuhrman grades
were same for both tumors.
Multiple authors have previously evaluated and correlated the variability of FDG uptake
to various subtypes of RCC and also to Fuhrman grading. In the largest study of 68
patients, Bertagna et al. found no significant statistical correlation between FDG
PET/CT results and Fuhrman grade or histology subtype of primary tumor.[4] The present case is an excellent example of variable FDG uptake in RCC. The patient
has developed bilateral synchronous RCC under similar carcinogenic influence still
they have different metabolic characteristics. The only histological difference between
these renal masses is presence of LVI and necrosis in FDG avid lesion.
LVI is a well-known independent risk factor of poor prognosis in many malignancies.
Studies also report that RCCs without LVI have longer metastatic or disease-free survival
and overall survival.[5]
FDG PET/CT is the fastest growing onco-imaging modality where more and more authors
are correlating biological information obtained from FDG uptake with molecular prognostic
marker and clinical outcomes. Among common malignancies such as esophageal, lung,
and colorectal cancers, the SUVmax values assessed by PET correlate with patient's outcomes. Studies had previously
shown that high tumor glucose metabolism is a cellular characteristic that correlates
with the aggressiveness of tumors.[6] SUVmax values of RCC provide valuable prognostic information.[7] Namura et al. evaluated 26 patients of advanced RCC and compared SUVmax values of renal primaries with overall survivals of patients. They concluded that
RCC patients with high values of SUVmax could demonstrate poor clinical outcome.[8] In our case, the FDG-avid lesion in the left kidney shows LVI and necrosis on histology
[Figure 1] and [Figure 2], which in turn suggests the more aggressive nature of the left renal primary. Increased
glucose metabolism in this lesion is in consideration with above discussion about
aggressiveness and FDG uptake.
Although TNM stage, Fuhrman grade, and histological findings such as LVI and coagulative
necrosis are widely recognized prognostic factors in RCC,[9],[10] research continues to determine strong and easily available prognostic parameters
that could help to identify patients with aggressive disease before starting treatment.
FDG PET/CT can be an ideal modality in such a case as it not only provides complete
TNM staging of patients but also the prognostic information obtained in the form of
FDG uptake is valuable too.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
