Renal oncocytosis: imaging considerations

99mTc-MIBI SPECT/CT in a Case of Renal Oncocytosis

ABSTRACT

Renal oncocytosis is a very rare oncologically indolent form of renal neoplasia characterized by diffuse involvement of renal parenchyma by numerous oncocytic nodules. We describe contrast-enhanced CT and 99mTc-MIBI SPECT/CT findings in a patient with renal oncocytosis presenting with metachronous bilateral renal tumors. Contrast-enhanced CT showed numerous tumors ranging from several millimeters up to 3.9 cm in the left kidney. The tumors showed hypervascularity in the corticomedullary phase and washout in the excretory phase mimicking renal cell carcinoma. The larger tumors showed higher 99mTc-MIBI uptake than the adjacent renal parenchyma, suggesting renal oncocytoma confirmed by biopsy.

Emerging entities in renal cell neoplasia: thyroid-like follicular renal cell carcinoma and multifocal oncocytoma-like tumours associated with oncocytosis

The list of accepted entities of renal cell neoplasia has burgeoned since the turn of the century through recognition of rare tumour types and the discovery of genetic mutations driving renal neoplasia syndromes. This growth has not finished and in this report we present examples of each of these types which were not included in the 2016 World Health Organization classification of renal neoplasia, but are candidates for inclusion in the next edition of the classification. Thyroid-like follicular renal cell carcinoma is a rare tumour type with a distinctive microscopic appearance resembling follicles of the thyroid gland. Thirty-nine cases have been described and the findings have been reasonably consistent. Oncocytoma-like tumours associated with oncocytosis arise as a result of somatic mutations in the mitochondrial genome. The differential diagnosis is mainly with the renal lesions of the Birt-Hogg-Dubé syndrome, which is the result of germline mutations in the folliculin gene. Patients with oncocytoma-like tumours associated with oncocytosis are at great risk of developing renal failure as the proliferating lesions replace the renal parenchyma. Oncocytoma-like tumours have never been found to metastasise.

Computed Tomography Appearance of Renal Hybrid Oncocytic/Chromophobe Tumors

OBJECTIVE

A series of renal hybrid oncocytic/chromophobe tumors (HOCTs) was retrospectively assessed for morphologic features and enhancement characteristics by computed tomography (CT).

MATERIALS (SUBJECTS) AND METHODS

Nine patients with pathologically proven HOCTs were identified. These patients harbored a total of 12 lesions. All patients had available preoperative contrast-enhanced CT examinations, although a proportion of the studies had been carried out at outside institutions. The morphologic characteristics and enhancement patterns of each tumor were evaluated systematically.

RESULTS

Seventy-eight percent of the patients were men, with a mean age of 62 years. None of the patients had evidence of metastatic disease at the time of surgery. Mean tumor diameter was 4.4 cm. All the lesions were solid and well circumscribed. Calcifications were not seen in any of these masses. Thirty-three percent of the tumors demonstrated a central stellate hypodensity pattern, whereas a further 42% of the tumors demonstrated a heterogenous appearance. Mean attenuation values were 25.7 HU (noncontrast), 77.4 HU (arterial), 124.8 HU (venous), and 76.8 HU (delayed). Tumor-to-cortex ratios for the 2 enhanced phases (arterial and venous) were 0.56 and 0.79, respectively.

CONCLUSIONS

A series of HOCTs were found on CT to have 2 distinct patterns-a heterogenous enhancement pattern and an "oncocytoma-like" pattern with a central stellate hypodensity. Although the prospective diagnosis of HOCTs on the basis of CT findings is unlikely, an awareness of the existence of these lesions is important as new means of characterizing renal masses on imaging arise.

Unilateral renal oncocytosis and combined hybrid tumor: a case report and review of the literature

Renal oncocytosis is a very rare cause of multiple renal masses. Imaging features of renal oncocytosis and combined tumors have rarely been reported. Here, we describe a case of unilateral left renal oncocytosis and a combined hybrid tumor between chromophobe renal cell carcinoma and oncocytoma, which were depicted on CT and MR imaging as multiple enhancing solid masses with one dominant mass. Additionally, we reviewed the literature.

Renal oncocytosis: management and clinical outcomes

PURPOSE

Renal oncocytosis is a rare pathological condition in which renal parenchyma is diffusely involved by numerous oncocytic nodules in addition to showing a spectrum of other oncocytic changes. We describe our experience with renal oncocytosis, focusing on management and outcomes.

MATERIALS AND METHODS

A total of 20 patients with a final pathological diagnosis of renal oncocytosis from July 1995 through June 2009 were included in the analysis. Patient demographics, intraoperative variables and postoperative outcomes are reported.

RESULTS

Median age at nephrectomy was 71 years (IQR 59-75). Of the patients 15 (75%) had bilateral disease. There were 23 operations (9 right side, 14 left side) performed on 20 patients, and of these procedures 13 (57%) were partial nephrectomies and 10 (43%) were radical nephrectomies. Median dominant tumor mass diameter was 4.1 cm (IQR 3-6.4, range 1 to 14.6). The most common dominant tumor histology was hybrid tumor between oncocytoma and chromophobe renal cell carcinoma in 13 of 23 specimens (57%), followed by chromophobe renal cell carcinoma in 6 (26%), oncocytoma in 3 (13%) and conventional renal cell carcinoma in 1 (4%). Ten patients (50%) had preexisting chronic kidney disease before nephrectomy and chronic kidney disease developed in 5 more after surgery. After a median followup of 35 months no patients had metastatic disease.

CONCLUSIONS

Patients with renal oncocytosis usually present with multiple and bilateral renal nodules. Half of the patients had chronic kidney disease at diagnosis and 25% had new onset of chronic kidney disease. No patient had distant metastatic disease during followup. Our management approach is to perform partial nephrectomy when possible and then use careful surveillance of the remaining renal masses.