Oncocytoma with a vascular extension, associated with a papillary carcinoma: A case report

Abstract

This is a case report about a patient which presents with two right renal tumors, one of them being an oncocytoma with typical histopathological features and renal vein extension. Recent studies show that despite renal vein thrombus being a histological sign of malignancy; when associated with renal oncocytoma, it should not alter the benign prognosis of oncocytoma, and a simple follow-up may be carried. Further explorations should be done when easily available, and when the histopathologic diagnosis of oncocytoma is uncertain, to rule out the differential diagnosis of a chromophobe renal cell carcinoma, oncocytic variant.

1. Introduction

Renal oncocytoma is considered as a benign epithelial lesion diagnosed histologically. Its surgical excision is usually required as it cannot be distinguished with certainty from renal cell carcinomas based on clinical and radiological findings.¹

Amongst the most uncommon findings in oncocytoma is vascular invasion.¹ These finding warrants a thorough consideration of the differential diagnosis of chromophobe renal cell carcinoma, oncocytic variant. We report a rare case of an oncocytoma with renal vein thrombosis, associated with a papillary carcinoma.¹

2. Case presentation

A 46-year-old male, with a history of secondary hypertension and chronic kidney disease undergoing hemodialysis, presented to our outpatient department with chronic right flank pain without gross hematuria being reported.

An ultrasound showed two right renal solid masses. Further exploration with a CT scan showed two small kidneys; the right kidney containing two organ-confined solid masses, with no evident vascular extension.

The first one is an exophytic ovoid mediorenal mass of 40-mm in its largest diameter, with an identified capsule, that has the same renal parenchymal density and that contains hemorrhagic remodeling. It's mildly enhanced after intravenous iodine solution injection (Fig. 1a). The second one is an upper pole renal mass with the same characteristics as the first one, measuring 20 mm on its largest diameter (Fig. 1b). Renal vein was free of any thrombus or embolism (Fig. 1c).

Fig. 1.

Computed tomography shows chronic kidney disease features: a: right mediorenal exophytic tumor. b: upper polar cortical tumor. c: permeable right renal vein.

The patient underwent a right open radical nephrectomy with no per or post-operative adverse event. Intra-operatively, a small right kidney that contains two tumors with no macroscopic extension to the peri-renal fat nor to the renal vein.

Histologic findings after nephrectomy showed two right renal tumors. The first one being medio-renal of 30 × 30 mm, with a mahogany brown surface, without extension to the peri-renal fat, well circumscribed with a capsule, reaching renal hilum where it is responsible of a renal vein extension. Both the tumor and the renal vein embolism are formed with large cells containing abundant, granular eosinophilic cytoplasm, and a central, round nucleus which mainly contains single prominent nucleolus, organized in nests of bland cells embedded in a thin fibromyxoid stroma. No fibrous central scar was found, nor vascular wall invasion. This description fits well with an oncocytoma responsible of a vascular extension(Fig. 2). The second tumor is upper polar 23 × 20 mm mass, limited to the renal parenchyma, with an orange surface, that contains cubic and polygonal cells with a cytoplasm that is mainly basophilic, sometimes clear, and a round slightly atypical nucleus. These cells are organized in a papillary architecture that fits with papillary carcinoma type 1.

Fig. 2.

a: Oncocytoma with vascular invasion (x40), b: Oncocytoma: solid growth pattern with granular eosinophilic cytoplasm (x200), c: Papillary carcinoma (x200).

3. Discussion

Renal oncocytoma is usually a solitary tumor with a benign prognosis. Its association with papillary renal cell carcinoma has already been described but it's extremely rare. The prognosis is related to the papillary renal cell carcinoma.² The presence of vascular extension in a renal tumor is an established feature of malignancy, and the association with a presumably benign tumor such as oncocytoma should evoke the differential diagnosis of a chromophobe renal cell carcinoma, oncocytic variant.

Diagnostic certainty requires an immunohistochemistry anti-CK 7 screening, and a FISH (Fluorescence In Situ Hybridization) analysis showing a rearrangement of the cyclin D1 (CCND1).^3,4 Authentic renal oncocytomas with renal vascular embolism were already described, and the benign aspect of the tumor can be retained with quite certainty, when the morphologic and histologic features are typical (as shown in our case).¹

In fact, a multicentric study carried at 3 large medical centers in the US in 2016, identified 22 cases of vascular extension of 1474 renal oncocytoma (1,5%). In this series, IHC for CK7 was not available for most cases. The cohort showed no metastasis or recurrence and overall survival of 94.7% at 2.5 years following diagnosis.¹ Other studies showed that renal oncocytomas with extension to the renal vein or its branches have the same morphological, immunohistochemical, and cytogenetic findings as have their counterparts without evidence of intravascular invasion. In those studies, all patients were alive and free of tumors with follow-up of 1–5 years.⁵

4. Conclusion

We reported a rare case of a renal oncocytoma with vascular invasion, associated to a papillary carcinoma. Studies showed that when the histological aspect is typical of an oncocytoma, a thrombus into the renal vein is rare, and should not lead to any uncertainty of the benign character of the tumor. Most studies support the finding that vascular invasion does not alter the favorable prognosis of oncocytoma. However, the differential diagnosis of chromophobe renal cell carcinoma, oncocytic variant, should be put into consideration, and further immunohistochemical and genetic screening should be done.

Consent

Signed consent was obtained from the patient.

Declaration of competing interest

The authors declare that there are no conflicts of interest regarding the publication of this article.