Editor: Mahmut Akgul (

2022-34/September 5

Contributors: Fanni Santa, Levente Kuthi

A 69-year-old male with macroscopic hematuria and low back pain was admitted to the Department of Urology. Two years earlier, the inferior lobe of his left lung was removed because of pulmonary adenocarcinoma. After that, the patient received chemo- and radiotherapy and was tumor-free. A contrast-enhanced abdominal CT was recently performed that revealed a 13-cm-large tumor in the left kidney. A radical nephrectomy was performed. 



a) Renal cell carcinoma, unclassified

b) Metastatic pulmonary adenocarcinoma

c) Composite oncocytoma and clear cell renal cell carcinoma

d) Hybrid oncocytic/chromophobe tumor

e) Metastatic pulmonary adenocarcinoma to oncocytoma

Composite oncocytoma and clear cell renal carcinoma

Composite tumors of the kidney are rare, with mainly case reports and one case series in the literature. The majority of these tumors are composed of oncocytoma or chromophobe renal cell carcinoma (RCC) and papillary adenoma or papillary RCC; however other combinations were reported. The dominance of the oncocytic tumors in this scenario was explained by the lack of the pseudocapsule in pink tumors, but the exact mechanism is not fully understood. For therapeutic implications, the recognition of any malignant component is essential.

Although the diagnosis is usually straightforward in nephrectomy specimens like ours, diagnostic difficulties may be raised in limited material, like in core biopsy. Concerning our case, firstly, eosinophilic cytoplasm tumor cells are frequently admixed with clear cell morphology, and secondly, due to the heterogeneity, a diverse architecture is commonly appreciated in clear cell RCC.

Immunohistochemistry is helpful in a similar case since clear cell RCC expresses carbonic anhydrase 9, while oncocytoma is positive with CD117. In our opinion, cytokeratin 7 (CK7) and vimentin have a minimal role because focal CK7 expression can be observed in clear cell RCC, and some degree of vimentin positivity is present in more than 70% of oncocytomas. In addition, composite tumors can be built-up by an organ’s primary tumor and a metastatic tumor of another organ. This cancer to cancer metastasis is exceptionally rare, and the issue is again with the biopsy samples. In this clinical scenario, the pathologists must rely on the clinical data, if there is any and immunohistochemistry. PAX8 is regarded as the most specific marker of renal cell neoplasm and is not expressed in the most frequent carcinomas with high metastatic potential (lung, prostate, breast, and large intestine). Genetic investigations usually have nothing to do with renal composite tumors.

Goyal R, Parwani AV, Gellert L et al. A collision tumor of papillary renal cell carcinoma and oncocytoma: case report and literature review. Am J Clin Pathol. 2015 Nov;144(5):811-6.

Williamson SR, Cheng L, Gadde R et al. Renal cell tumors with an entrapped papillary component: a collision with predilection for oncocytic tumors. Virchows Arch. 2020 Mar;476(3):399-407.

Hes O, Michal M, Kuroda N et al. Vimentin reactivity in renal oncocytoma: immunohistochemical study of 234 cases. Arch Pathol Lab Med. 2007 Dec;131(12):1782-8.

Fanni Santa, Levente Kuthi
Department of Pathology
Albert Szent-Györgyi Medical School, University of Szeged
Szeged, Hungary


Composite renal tumor, oncocytoma, clear cell renal cell carcinoma