- Case report
- Open Access
- Open Peer Review
A back-to-back tumor composed of papillary renal cell carcinoma and oncocytoma treated by laparoscopic partial nephrectomy: a case report
© The Author(s). 2018
- Received: 12 February 2018
- Accepted: 19 March 2018
- Published: 21 May 2018
Renal oncocytoma is the most common benign renal tumor, and papillary renal cell carcinoma is the second most common histologic subtype of renal cell carcinoma. Renal tumors containing different components such as papillary renal cell carcinoma and oncocytoma are extremely rare.
A renal mass was incidentally detected in a 52-year-old Korean woman, and a computed tomographic scan showed a 32-mm multicystic mass with some calcifications in the lower pole of the right kidney. She underwent laparoscopic partial nephrectomy without any perioperative complications. We found a papillary renal cell carcinoma and an oncocytoma in a tumor mass.
The possibility of a mixed malignant tumor should be considered while treating benign tumors such as oncocytoma.
- Collison tumor
- Hybrid tumor
- Laparoscopic partial nephrectomy
- Papillary renal cell carcinoma
- Renal oncocytoma
Renal oncocytoma is the most common benign renal tumor. It appears as an enhancing renal mass on computed tomographic images and is indistinguishable from renal cell carcinoma (RCC). It accounts for 3% to 7% of all kidney tumors . It is derived from intercalated cells of distal renal tubules. Papillary renal cell carcinoma (PRCC) is the second common histologic subtype of RCC, and it accounts for 10% to 15% of all RCCs . PRCC can be divided into subtypes 1 and 2; subtype 2 is a more aggressive subtype . PRCC arises from proximal renal tubules. Occasionally, it has been reported that hybrid tumors of the kidney contain chromophobe RCC and oncocytoma, because they are a closely related spectrum of neoplasms, although one is benign and the other is malignant. However, other hybrid tumors of the kidney are very rare, and we report a case of a patient with a back-to-back tumor that contained oncocytoma and PRCC components.
In December 2015, an asymptomatic 52-year-old Korean woman with hypertension was referred to our hospital because of a right-sided renal mass detected on transabdominal ultrasound. She was a housewife and did not have any medical history. Her physical examination was unremarkable, and routine laboratory studies did not document any abnormalities (creatinine 0.47 mg/dl, normal complete blood count, normal liver function test, normal serum electrolyte concentrations, microscopic hematuria 2+).
The preoperative creatinine level was 0.47 mg/dl, and the estimated glomerular filtration rate (eGFR) calculated by the Modification of Diet in Renal Disease equation was ≥ 120 ml/minute/1.73m2. At the 12-month follow-up after surgery, the patient’s creatinine level was 0.52 mg/dl, and her eGFR was ≥ 120 ml/minute/1.73m2. There was no evidence of recurrence on chest or abdominal CT.
We report the characteristics of a hybrid tumor of the kidney. This tumor is occasionally called a “collision tumor.” The term collision tumor refers to coexistent but independent tumors that are histologically distinct . Collision tumors in the kidney have been described, and they mostly have included oncocytoma and chromophobe RCC. Hereditary disease such as Birt-Hogg-Dubé syndrome shows coexistence of oncocytoma and other RCCs of an origin similar to that of chromophobe RCC . PRCC and oncocytoma have different cellular origins, and therefore such a hybrid tumor is very rare.
Previously reported cases of hybrid tumor composed of papillary renal cell carcinoma and oncocytoma
PRCC size (cm)
Rowsell et al. 
Floyd et al. 
Sejben et al. 
Vasuri et al. 
Ozer et al. 
Goyal et al. 
Oncocytoma is a common benign tumor, and occasionally a small renal mass such as a benign tumor is treated with active surveillance or ablation. We treated this ambiguous tumor by laparoscopic partial nephrectomy. The possibility of a mixed malignant tumor should be considered while treating benign tumors such as oncocytoma.
No funding was received.
Availability of data and materials
The datasets used and/or analyzed during the present study are available from the corresponding author on reasonable request.
TSK conceived of and designed the report. WTS and YHJ acquired data. SHK analyzed and interpreted data. PMK drafted the manuscript. BKC critically revised the manuscript for important intellectual content. HYR provided supervision. All authors read and approved the final manuscript.
Ethics approval and consent to participate
This study has been approved by institutional review board of the Kosin University Gospel Hospital.
Consent for publication
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
The authors declare that they have no competing interests.
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