Received: 18 July 2017
Accepted: 18 September 2017
Incidence and histologic features of mixed renal tumors
Neil J. Kocher MD
Chris Rjepaj BS
Erik Lehman MS
Jay D. Raman MD
Department of Surgery, The Pennsylvania
State University, College of Medicine,
Department of Public Health Sciences, The
Pennsylvania State University, College of
Medicine, Hershey, Pennsylvania
Jay D. Raman, MD, FACS, Professor and
Chief, The Pennsylvania State University,
College of Medicine, Department of Surgery,
Division of Urology, 500 University Drive,
H055, Hershey, PA 17033–0850.
Background and Objectives: Guidelines for management of renal cell carcinoma (RCC)
incompletely address the implications of mixed renal tumor histology. We investigate
the incidence of mixed renal tumors identified at renal surgery and determine the
association with pathologic features.
Methods: Institutional kidney tumor database was reviewed to identify 536 patients
who underwent partial or radical nephrectomy. Clinical, demographic, and pathologic
data were collected. A linear fixed effects model and logistic regression determined the
association of mixed tumor histology with tumor size, stage, grade, and nephrometry
Results: Three hundred and eighteen men and 218 women with a median BMI of 31
and median tumor size of 3.5 cm were included. 469 (87.5%) patients had pathologic
kidney cancer with the most common histologies being clear cell carcinoma in 343
(73.1%) patients, papillary in 81 (17.3%) patients, and chromophobe in 25 (5.3%)
patients. Twenty (4.3%) patients had mixed tumors on final pathology. Clear cell RCC
was the most common primary pathology in patients with mixed tumor histology
(n = 14, 75%) with additional primary tumor histologies included papillary and
chromophobe. When considering secondary histologies, 85% were coexistent primary
renal cancers while 15% (n = 3) were benign renal tumors. No association of mixed
tumor histology and adverse pathologic features was noted.
Conclusions: Mixed tumor histology is an uncommon entity that is not associated with
adverse features in a solitary renal mass. These results are especially relevant in
discussing the role of renal mass biopsy, and provide further evidence that renal
sampling is a valuable tool in the appropriate clinical context.
kidney cancer, mixed tumor histology, renal cell carcinoma
Neoplasms of the kidney and renal collecting system constitute
nearly 4% of new cancer diagnoses in the United States each
Increased detection of renal incidentalomas has paralleled
the rapid adoption of cross-sectional imaging as a diagnostic tool.
The vast majority of enhancing, solitary renal masses consist of
clear cell, or papillary renal cell carcinoma (RCC), whereas benign
lesions are more commonly either angiomyolipoma or renal
The differential diagnosis for a solid renal mass
also includes several more uncommon albeit histologically distinct
Hybrid renal tumors are classically associated with Birt-Hogg-
Dubé syndrome or renal oncocytosis, however multiple reports have
highlighted sporadic cases in patients without a genetic predisposi-
Hybrid renal tumors are specifically those lesions containing
elements of chromophobe RCC and renal oncocytoma.
with hybrid RCC are recognized to have excellent oncologic outcomes
© 2017 Wiley Periodicals, Inc. wileyonlinelibrary.com/journal/jso J Surg Oncol. 2018;117:430–433.