Renal oncocytoma: a clinicopathologic study of 70 cases

Synchronous colonic adenocarcinoma and renal oncocytoma: a case report and literature review

We present the case of a patient with an adenocarcinoma of the colon associated with an oncocytoma of the kidney. A left colonic cancer was diagnosed at colonoscopy and an incidental finding of a left renal mass was noted, with a staging computerized tomography scan. Following a left hemicolectomy and a left nephrectomy, the pathological report confirmed the presence of a colonic adenocarcinoma and revealed that the left renal mass was an oncocytoma. This case report reviews the management decisions associated with incidental renal masses as well as the treatment of synchronous neoplasia.

Case report of a symptomatic giant renal oncocytoma

Renal oncocytomas are benign tumours, often asymptomatic, and picked incidentally on radiological imaging. We present a case report of a symptomatic giant renal oncocytoma in a 61-year old man having lower back/right flank pain. A large right renal mass was identified on abdominal CT scan. Radiological features were not sufficient to differentiate this lesion from renal cancer. Right radical nephrectomy was performed. Typical features of oncocytoma, without evidence of malignancy, were seen on histological examination of the specimen. In this report, we discuss literature review of radiological, genetic, and pathological characteristics of renal oncocytoma.

Incidental Bilateral Renal Oncocytoma in a Patient with Metastatic Carcinoma of Unknown Primary: a Pitfall on (18)F-FDG PET/CT

Bilateral renal masses are uncommon but can raise a strong suspicion of primary or secondary malignancy, especially during the initial work-up of an oncology patient. Renal oncocytomas are benign renal tumors that are commonly discovered incidentally on diagnostic imaging with a small percentage occurring bilaterally. Although (18)F-FDG uptake in renal oncocytomas has been described, a case of a bilateral (18)F-FDG-avid renal oncocytoma has not been previously reported in the literature. A variety of malignant causes of bilateral (18)F-FDG positive renal masses are known, however it is important to include this benign etiology in the differential diagnosis. We report an unusual case of an incidental bilateral renal oncocytoma evaluated with contrast enhanced CT and (18)F-FDG PET/CT.

Oncocytic mania: a review of oncocytic lesions throughout the body

Oncocytic lesions are characterized pathologically by an abundance of oncocytes, that is by enlarged, eosinophilic, and finely granular cells enriched in mitochondria. They can arise in numerous organs and tissues, often in endocrine glands, and have been associated with hyperplasia, autoimmunity, and neoplasia. The causes and mechanisms that transform a normal cell into an oncocyte remain to be elucidated. Aim of this article is to review the most common oncocytic lesions, highlighting their key pathological features and clinical significance.

Renal oncocytoma revisited: a clinicopathological study of 109 cases with emphasis on problematic diagnostic features

AIM

To evaluate problematic diagnostic features in renal oncocytoma.

METHODS AND RESULTS

One hundred and nine cases of oncocytoma were reviewed and the problematic gross and microscopic features recorded. Multifocal and bilateral neoplasms were found in 12 (11%) and five (4.6%) cases, respectively. Haemorrhage was seen grossly in 30 (27.5%) neoplasms and a central scar was identified in 35 (32.1%). On microscopy, perinephric fat extension was present in 17 (15.6%) neoplasms and vascular extension was identified in four (3.7%) oncocytomas. Rare mitoses and focal coagulative necrosis were identified in two (1.8%) cases each. Focal clear cell changes were found in 16 (14.7%) oncocytomas, typically within hyalinized areas. Limited foci with chromophobe-like histology (not exceeding 5% of the neoplasm) were found in 13 (11.9%) oncocytomas. In 12 (11%) oncocytomas, rare papillary formations were noted in the lumina of microcysts. Significant nuclear atypia, oncoblasts and entrapped tubules were identified in 27 (24.8%), 41 (37.6%) and 40 (36.7%) neoplasms, respectively. After a median follow-up of 52 months (range 1-113 months), there was no disease recurrence, progression or death attributed to oncocytoma.

CONCLUSIONS

The recognition of the spectrum of morphological changes observed in renal oncocytoma should help pathologists establish a diagnosis of oncocytoma in problematic cases.

Oncocytoma of the kidney with prominent intracytoplasmic lumina

Oncocytoma is a histologically distinctive neoplasm of the kidney, with a well-recognized cytoarchitectural appearance. On occasion, however, renal oncocytomas are known to exhibit unusual morphologic features that may pose diagnostic difficulties. We present the clinical and pathologic details of an oncocytoma of the kidney with an unusual histologic appearance imparted by the presence of large numbers of prominent intracytoplasmic lumens. Morphologically, the neoplasm was composed of uniform polygonal cells with copious amounts of granular, eosinophilic cytoplasm, round nuclei, and prominent nucleoli, exhibiting an organoid pattern of growth. Intracytoplasmic lumina of varying size were present throughout the tumor. There were no mitotic figures or areas of necrosis present. The diagnosis of oncocytoma was supported by immunohistochemical and ultrastructural studies. By electron microscopy, the intracytoplasmic lumens appeared as membrane bound spaces with associated microvilli. The presence of intracytoplasmic lumina in a significant proportion of cells is an uncommon feature of renal oncocytoma which can generate problems in diagnosis. Awareness of this phenomenon should allow for improved recognition of oncocytomas exhibiting this type of unusual morphology.

MRI features of renal oncocytoma and chromophobe renal cell carcinoma

OBJECTIVE

The purpose of this study was to retrospectively describe the MRI features of the pathologically related entities renal oncocytoma and chromophobe renal cell carcinoma (RCC).

MATERIALS AND METHODS

Twenty-eight cases of histologically proven renal oncocytoma and 15 of chromophobe RCC evaluated with preoperative MRI from January 2003 through June 2009 at our institution were independently reviewed for an array of MRI features by two radiologists blinded to the final histopathologic diagnosis. These features were tabulated and compared between chromophobe RCC and renal oncocytoma by use of the Mann-Whitney test and binary logistic regression.

RESULTS

Renal oncocytoma and chromophobe RCC showed no significant difference in size or any of 16 qualitative imaging features (p = 0.0842-1.0, reader 1; p = 0.0611-1.0, reader 2). Microscopic fat, hemorrhage, cysts, infiltrative margins, perinephric fat invasion, renal vein invasion, enhancement homogeneity, and hypervascularity were each observed in less than 20% of cases by both readers. A central scar and segmental enhancement inversion (a recently described finding in which early contrast-enhanced images show relatively more enhanced and less enhanced intralesional components with inversion of their relative enhancement on later images) were observed by both readers in at least 10% of cases of both renal oncocytoma and of chromophobe RCC with no significant difference between the two entities (p = 0.2092-0.2960).

CONCLUSION

We have presented the largest series to date of the MRI features of both renal oncocytoma and chromophobe RCC. These related entities exhibited similar findings, and no MRI features were reliable in distinguishing between them.

Molecular pathology of renal oncocytoma: a review

Differentiating renal oncocytoma from its renal cell carcinoma (RCC) mimics, particularly chromophobe RCC, can be difficult, especially when limited tissue is available for evaluation and requires sophisticated microscopic, ultrastructural and immunohistochemical evaluation. In this review, the relevant literature has been reviewed, and supporting data obtained by applying modern microarray-based technologies are discussed with a focus on molecular pathology of renal oncocytoma. The high resolution whole-genome DNA-microarray based analyses excluded with all certainty the occurrence of small specific alterations. Renal oncocytomas are characterized by variable chromosomal patterns. The number of genes selected by global gene expression analyses and their usefulness in the diagnostic pathology based on immunohistochemical evaluation is far below the expectations. The conflicting staining patterns, together with the poor specificity of proposed antibodies, leads us to believe that these candidate immunomarkers might not help in the separation of these tumors. Applying DNA based tools might help in the diagnosis of renal oncocytoma with uncertain histology. However, only the combination of all available techniques could give reliable information.

Imprint cytologic features of chromophobe renal cell carcinoma morphologically resembling renal oncocytoma: is this an oncocytic variant of chromophobe renal cell carcinoma?

In this article, we report a case of 76-year-old woman with a rare variant of chromophobe renal cell carcinoma (CRCC). Cytologically, renal tumor cells obtained from imprint cytology were isolated or arranged in small or monotonous population cells with abundant granular cytoplasm. Neoplastic cells showed regular and uniformly shaped small round to oval nuclei with smooth margin. Binucleation was occasionally seen. Immunocytochemically, the cytoplasm of almost all tumor cells was diffusely positive for vimentin and CK 7. Histologically, the cytoplasm was abundant granular eosinophilic and composed of solid cell sheets or pseudoacinar structures. Additionally, tumor cells showed infiltration into some small renal veins covered by a single layer of endothelial cells. These cytological and histological features entirely resembled those of renal oncocytoma. We performed the analysis of von Hippel-Lindau (VHL) gene mutation, 3p loss of heterozygosity (LOH), and fluorescence in situ hybridization (FISH) on chromosomes 7, 10, 13, 17, and 21. As a result, we confirmed monosomy of chromosomes 7, 10, 13, and 17, and these findings corresponded to the diagnosis of CRCC. Finally, we present a case of renal tumor morphologically resembling renal oncocytoma but genetically showing CRCC. We suggest that oncocytic variant of CRCC may actually exist.

Renal oncocytoma: a comparative clinicopathologic study and fluorescent in-situ hybridization analysis of 73 cases with long-term follow-up

Clinical studies have confirmed that renal oncocytoma (RO) is a benign neoplasm with excellent prognosis. In diagnostically challenging cases of renal oncocytic epithelial neoplasms, fluorescent in-situ hybridization (FISH) is increasingly being used and its ability to distinguish RO from chromophobe renal cell carcinoma (ChRCC) has been documented. In this study, we evaluated the differential diagnostic contribution of FISH in cases of RO.

Clinicopathologic data and glass slides from 73 patients with RO were reviewed; 20 cases of ChRCC were included for comparison. FISH analysis of formalin-fixed, paraffin-embedded sections was performed using centromeric probes for chromosomes 1, 2, 7 and 17. FISH analysis revealed ROs had frequent loss of signal for chromosome 1 (56%) and 17 (44%). Tumors with more than one loss were common (41%) and 10% cases showed loss of all chromosomes examined. A total of 18% cases did not show any abnormality.

Our study shows that chromosomal abnormalities in both ROs and ChRCCs are common with frequent loss of chromosomes 1 and 17. No association was found between overall patient survival and the extent of chromosomal abnormalities. FISH results, even those showing significant chromosomal abnormalities, should not alter the primarily morphology-based diagnosis of RO.

Giant renal oncocytoma: a case report and review of the literature

INTRODUCTION

Renal oncocytomas are benign neoplasms derived from cells of the distal renal tubule, and comprise 5% to 7% of primary renal neoplasms. Oncocytomas are mostly asymptomatic, and the majority of tumors are discovered incidentally. In this case report, we present a case of a patient with a giant oncocytoma arising from her left kidney.

CASE PRESENTATION

We describe a 25-year-old Turkish woman who was admitted to our hospital with abdominal pain and a 3-year palpable abdominal mass, which was found present since her second pregnancy. Examination revealed a 15 x 20-cm mass in her abdominal cavity. Computed tomography revealed a mass with regular outlines, measuring 18 x 11 x 12 cm, associated with the left kidney, and causing marked hydroureteronephrosis. We excised the mass and performed a left nephrectomy on our patient. The immunohistopathology of the mass was consistent with renal oncocytoma. No local or distant metastasis was seen at 6 months postoperatively.

CONCLUSION

To the best of our knowledge, this is the second largest renal oncocytoma described in the English language literature. This is also the first reported giant oncocytoma that presented during pregnancy.

Contrast enhanced ultrasound of renal masses

Contrast enhanced ultrasound (CEUS) has gained clinical importance over the last years for the characterization of hepatic masses. Its role in extrahepatic indications has been investigated repeatedly but has been less comprehensively studied. Currently more than 50% of renal masses are incidentally diagnosed, mostly by B-mode ultrasound. The method of choice for characterization of renal lesions is contrast enhanced computed tomography (CECT). In the case of cystic lesions CECT refers to the Bosniak classification for cystic lesions to assess the risk of malignant behavior. The majority of masses are renal cell carcinoma, but the exact proportion is controversial. Disadvantages of CECT are a significant risk for patients with impaired renal function, allergic reactions and hyperthyroidism due to iodinated contrast agents. Several studies concerning CEUS for the characterization of both solid and cystic renal lesions have been published, but prospective multicenter studies are missing, the presented data being mainly descriptive. The aim of the this manuscript is to review the current literature for CEUS in renal masses, to summarize the available data and focus on possible concepts for studies in the future.

Unilateral simultaneous renal oncocytoma and angiomyolipoma: case report

A rare case of synchronous angiomyolipoma and oncocytoma in the same kidney of a 70 year old man is presented. A left renal mass was found incidentally by ultrasound. Computerized tomography and magnetic resonance imaging revealed a 1,3 cm mass in the mid-portion of the left kidney, whereas on the lower pole of the same kidney, a 3,3 cm mass was also revealed, consistent with angiomyolipoma. A working diagnosis of renal cell carcinoma was made. A radical nephrectomy was performed. Microscopically, the tumor of the lower pole was found to be an angiomyolipoma, whereas the mid-portion tumor was an oncocytoma. Until now, only 16 cases of unilateral simultaneous presence of renal angiomyolipoma and oncocytoma have been reported. Of these cases, all except one were female and three were associated with the tuberous sclerosis complex. It is well worth remarking, that renal oncocytoma overlap with other renal neoplasms, therefore nephrectomy remains the treatment of choice.Renal angiomyolipoma and oncocytoma are uncommon neoplasms and their simultaneous presence in the same kidney is rare. Only 16 cases have been reported until now in the literature. The purpose of this paper is to present an additional case without evidence of tuberous sclerosis.

Renal Oncocytoma in Taiwan

BACKGROUND

Renal oncocytoma has been repeatedly reported in Western countries, but only a few cases have been reported in Eastern countries. This study aims to review the clinical course of renal oncocytoma in an Eastern country such as Taiwan.

MATERIALS AND METHODS

Sixteen cases of renal oncocytoma seen between 1987 and 2002 at Chang Gung Memorial Hospital, Taipei, Taiwan, were studied.

RESULTS

Preoperatively, all patients were diagnosed to have renal cell carcinoma, following various radiologic studies. Perioperatively, frozen sections of three patients indicated renal oncocytoma in two and renal cell carcinoma in one. Renal oncocytoma has marked similarities to renal cell carcinoma, according to various radiologic, cytologic, and pathological investigations, so an accurate diagnosis is difficult to achieve, either preoperatively or perioperatively. Therefore, rather than being treated with partial nephrectomy, all patients were treated aggressively with unilateral radical nephrectomy. Postoperatively, all 16 patients were followed up, from 12 to 189 months, with a mean of 58.7 months. Notably, all patients survived with no evidence of tumor recurrence.

CONCLUSIONS

The experience in Taiwan is generally that renal oncocytoma behaves benignly, as reported in other areas. The excellent prognosis associated with this tumor appears to indicate that partial nephrectomy may suffice for removing the tumor, while sparing other unaffected renal parenchyma.

Segmental enhancement inversion at biphasic multidetector CT: characteristic finding of small renal oncocytoma

PURPOSE

To retrospectively determine the usefulness of segmental enhancement inversion during the corticomedullary phase (CMP) and early excretory phase (EEP) of biphasic multidetector computed tomography (CT) in differentiating small renal oncocytoma from renal cell carcinoma (RCC).

MATERIALS AND METHODS

This retrospective study was institutional review board approved; informed consent was waived. Between January 2004 and December 2006, 98 patients with pathologically confirmed renal masses smaller than 4 cm (10 renal oncocytomas and 88 RCCs) were included in this study. Segmental enhancement inversion was defined as follows: In a mass with two segments showing different degrees of enhancement during CMP, the relatively highly enhanced segment became less enhanced during EEP, whereas the less-enhanced segment during CMP became highly enhanced during EEP. Two experienced radiologists retrospectively assessed the presence of segmental inversion in all masses and measured attenuation with consensus. The Fisher exact test was used to determine the significance of segmental enhancement inversion in differentiating small renal oncocytoma from RCC.

RESULTS

Eight of 10 renal oncocytomas and only one of 88 RCCs showed segmental inversion during CMP and EEP, which significantly differentiated small renal oncocytomas and RCCs (P < .0001). For differentiating oncocytoma from RCC, segmental inversion was found to have a sensitivity of 80% (eight of 10), a specificity of 99% (87 of 88), a positive predictive value of 89% (eight of nine), and a negative predictive value of 98% (87 of 89). The mean values of the attenuation differences shown by two segments during CMP and EEP were 62.75 HU +/- 36.96 (standard deviation) and -36.88 HU +/- 20.02, respectively.

CONCLUSION

Segmental enhancement inversion during CMP and EEP was found to be a characteristic enhancement pattern of small renal oncocytoma at biphasic multidetector CT and it may help in differentiating small oncocytoma from RCC.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/2522081180/DC1.

Renal oncocytoma: CT features cannot reliably distinguish oncocytoma from other renal neoplasms

AIM

To retrospectively review the computed tomography (CT) imaging features of a series of histologically confirmed renal oncocytomas and to determine whether imaging features are predictive of this subtype of benign renal epithelial tumour.

MATERIALS AND METHODS

From May 2001 to October 2007, 21 patients with 28 renal masses, confirmed as renal oncocytoma on histological examination of the resection specimen, were identified from the pathology database at our institution. The preoperative imaging findings were retrospectively analysed to determine characteristic features, if any, to predict this rare subtype of benign renal tumour.

RESULTS

There were 11 female and 10 male patients and the age at presentation ranged from 40-80 years (mean age 65.9 years). The size of the masses ranged from 1.2-12 cm in diameter (mean diameter 4.9 cm). All masses showed contrast enhancement. In 18 (64.3%) lesions the enhancement of the tumour was isodense to renal cortex. Ten (35.7%) lesions were hypodense to renal cortex. In three (10.7%) lesions, a well-defined stellate central scar was seen at CT and confirmed pathologically. In two (7.1%) lesions, a central scar was identified pathologically, but not seen on CT. The size of the central scars ranged from 10-29 mm diameter on CT. Twenty-two (78.6%) lesions did not demonstrate a scar on CT or pathologically. None of the patients had regional lymphadenopathy or distant metastasis.

CONCLUSION

Renal oncocytoma is typically described as being hypervascular and homogeneous, with a characteristic central stellate scar on CT. The present study demonstrates that these imaging features are found in only a small proportion of these tumours. Therefore, imaging characteristics alone are unreliable when differentiating between oncocytoma and renal cell carcinoma, and histopathological diagnosis remains the reference standard.

Pathologic Features of Adult Renal Cortical Tumors

In the past few years, a much better understanding of the morphologic spectrum of renal cortical tumors has resulted in a clinically highly relevant contemporary classification system of these tumors. The current and still evolving era of targeted therapies in kidney cancer further highlights the importance of the appropriate pathologic classification. The recently gained knowledge about molecular-driven antigen expression almost certainly will have a major role to play in the characterization, development, and evaluation of targeted therapies in kidney cancer in the future.

Claudin-7 and claudin-8: immunohistochemical markers for the differential diagnosis of chromophobe renal cell carcinoma and renal oncocytoma

Claudin-7 and claudin-8 code for tight junction proteins expressed in distal nephron epithelium. In a recent oligonucleotide microarray study, we identified claudin-7 and claudin-8 as candidate markers to distinguish chromophobe renal cell carcinoma from other renal tumors, including oncocytoma. Distinction of these lesions can be difficult by light microscopy but is clinically important because chromophobe renal cell carcinoma has malignant biological potential, whereas renal oncocytoma is benign. Claudin-7 and claudin-8 expression was studied by immunohistochemistry in 11 chromophobe renal cell carcinomas and 17 oncocytomas using formalin-fixed paraffin-embedded tissue sections of tumor with adjacent nonneoplastic kidney. Steam antigen retrieval was performed before immunohistochemistry. Specificity was verified by negative control reactions without primary antibody and appropriate membranous staining patterns in positive control tissues (colon carcinoma and adjacent nonneoplastic kidney). Claudin-7 protein was expressed in a membranous pattern in 10 of 11 chromophobe renal cell carcinomas and 4 of 17 oncocytomas (P < .01). Claudin-8 was expressed in multiple patterns: In oncocytoma, 11 of 17 cases showed cytoplasmic, 4 of 17 membranous, and 2 of 17 negative reactions. In chromophobe renal cell carcinoma, 0 of 11 cases showed cytoplasmic, 3 of 11 membranous, and 8 of 11 negative reactions (P < .01). The immunohistochemical pattern of membranous claudin-7 and negative claudin-8 was seen in 7 of 11 chromophobe renal cell carcinomas and 1 of 17 oncocytomas (63% sensitivity, 84% specificity, 88% positive predictive value for chromophobe renal cell carcinoma). Negative claudin-7 and cytoplasmic claudin-8 were observed in 10 of 17 oncocytomas and 0 of 11 chromophobe renal cell carcinomas (59% sensitivity, 100% specificity and positive predictive value for oncocytoma). The distal nephron proteins claudin-7 and claudin-8 have potential use as immunohistochemical biomarkers in the differential diagnosis of chromophobe renal cell carcinoma and oncocytoma. Expression of claudin-7 and claudin-8 may reflect the relationship of chromophobe renal cell carcinoma and oncocytoma to intercalated cells of the cortical collecting duct. It may be necessary to identify additional biomarkers to include with claudin-7 and claudin-8 in a larger immunohistochemical panel to improve diagnostic sensitivity and specificity.

Renal oncocytoma with and without intravascular extension into the branches of renal vein have the same morphological, immunohistochemical and genetic features

We attempted to investigate the clinicopathological correlation of renal oncocytoma (RO) with renal vein extension. We identified seven ROs with extension into the branches of renal vein. The age of seven patients ranged from 61 to 82 years. Five cases were identified; incidentally, two patients had gross hematuria. After surgery, all patients were alive and free of tumors with follow-up of 1 to 5 years (mean=3.6). Oncocytomas measured from 2.2 to 7.5 cm. Renal vein extension was grossly suspected in 5/7 cases and histologically confirmed in all seven cases. Tumor cells were positive for cytokeratins, mitochondrial antigen, epithelial membrane antigen, and parvalbumin; 5/7 tumors were focally positive for cluster of differentiation 117. Ultrastructurally, the cytoplasm was packed by mitochondria. Molecular genetic analysis did not detect abnormal numbers of chromosomes 1, 2, 6, 7, 10, 17, and XY by fluorescence in situ hybridization, loss of heterozygosity on 3p, and mutation of Von Hippel-Lindau gene in all cases. Array comparative genomic hybridization analysis of two cases did not show any major genetic changes. Conclusions are: (1) renal oncocytomas may have intravascular extension to the branches of the renal vein; (2) renal oncocytomas with intravascular extension to the branches of the renal vein have the same morphological, immunohistochemical, and cytogenetic findings as have their counterparts without evidence of intravascular invasion; (3) the absence of metastases suggests an overall benign behavior of this tumor, but this has to be substantiated by further studies with a long-term follow-up; (4) in a renal tumor with granular cytoplasm showing renal vein extension, it is necessary to carefully exclude renal cell carcinomas (RCC) such as chromophobe RCC, oncocytic variant of papillary RCC, and granular variant of clear cell RCC.

A case of liver metastasis from an oncocytoma with a focal area of chromophobe renal cell carcinoma: a wolf in sheep's clothing

In 2004, the World Health Organization classified the renal oncocytomas as benign neoplasms of the kidney. There are reports of subtypes of renal tumors, with similar histological morphology to oncocytoma, but with malignant potential, one of these tumors is the eosinophilic variant of chromophobe renal cell carcinoma. It is important to characterize the histological features and the subtype of tumor, as this predicts biological behavior and cancer-specific survival rate. A rare case of a liver metastasis from a focal area of eosinophilic variant of chromophobe renal cell carcinoma mixed in oncocytoma in a 69-year-old woman is reported. Although some renal tumors may contain oncocytoma and eosinophilic variant of chromophobe renal cell carcinoma histology, caution should be exercised while diagnosing oncocytomas in needle biopsies as there may be unsampled area of chromophobe carcinoma which has a potential for metastatic spread representing a wolf in sheep's clothing.

Bilateral massive renal angiomyolipoma concurrent with oncocytoma in tuberous sclerosis complex associated with pulmonary lymphangioleiomyomatosis

We describe a patient with tuberous sclerosis complex and massive bilateral renal angiomyolipomas (AMLs) in association with pulmonary lymphangioleiomatosis, who experienced hemorrhagic shock because of rupture of the left renal AML. She was treated with transarterial embolization, followed by bilateral nephrectomy. The total tumor burden weighed 5800 g, making it the largest AML by weight in published reports. The histopathologic examination revealed concurrent oncocytomas with AMLs in the right kidney, indicating a possible shared mechanism in the pathogenesis of these two disorders. This case also represents a rare, but significant, overlap between renal AML, pulmonary lymphangioleiomatosis, and tuberous sclerosis complex.

Renal oncocytoma: clinical experience of Taipei Veterans General Hospital

BACKGROUND

Renal oncocytoma has been reported mostly in the Western literature, and only a few cases have been reported in Eastern populations. In the present study, we review the clinical course of renal oncocytoma in our institution.

METHODS

We obtained the files of 13 cases of renal oncocytoma between 1988 and 2006 from the pathological archives of Taipei Veterans General Hospital. We retrospectively analyzed the patients' characteristics, clinical manifestations, surgical technique and clinical outcome.

RESULTS

The study population comprised 10 men and 3 women, and the mean age at diagnosis was 59.6 years (range, 37-75 years). Twelve patients (92%) were asymptomatic at presentation and were incidentally diagnosed to have renal tumor by sonography (9 patients), computed tomography (1 patient) or magnetic resonance imaging (2 patients), and 1 presented with hematuria. The clinical impression of oncocytoma was made preoperatively in only 3 patients by imaging studies, and most of the patients (76.9%) were diagnosed with renal cell carcinoma before surgery. Ten were treated with radical nephrectomy, 2 with partial nephrectomy, and 1 received excisional biopsy. All patients had unilateral solitary renal tumor; the right kidney was involved in 7 cases (54%) and the left in 6 (46%). Mean tumor size was 5.3 cm (range, 2.7-8.5 cm). Three patients were lost to follow-up in our series, and there was no recurrence or death (100% disease-specific survival) in the remaining 10 patients (77%) who were followed-up for a mean duration of 53.2 months (range, 10-117 months).

CONCLUSION

Renal oncocytoma has a benign clinical course with excellent long-term outcomes. Currently, nephron-sparing surgery is the mainstay of treatment, especially in patients with small tumors. However, accurate preoperative diagnosis based only on imaging studies is difficult, and radical nephrectomy was performed for most of the patients in our series.

Chromophobe renal cell carcinoma with osseous metaplasia containing fatty bone marrow element: A case report

A 27-year-old woman presenting with epigastric pain and dyspepsia was found to have a calcified mass in the upper-middle right kidney. Gross examination of the nephrectomy specimen revealed a 6.5 x 5 x 4 cm renal tumor with dense calcification and ossification. Histopathological examination of the tumor showed solid, trabecular sheets and nesting of polygonal epithelial cells with abundant cytoplasm and prominent cell border and mature bony tissue enclosing fatty marrow. Renal cell carcinoma is frequently associated with calcification, but ossification is extremely rare. To our knowledge, we report the fourth case of a chromophobe renal cell carcinoma with extensive calcification and ossification.

Does Stage T3a Renal Cell Carcinoma Embrace a Homogeneous Group of Patients?

PURPOSE

Renal cell carcinoma invading the perinephric fat is classified as a stage T3a tumor in the 2002 TNM version. Based on long-term followup we examined the prognostic significance of this definition.

MATERIALS AND METHODS

We evaluated the outcome in 237 consecutive patients with localized renal cell carcinoma operated on between January 1985 and December 1997. Median followup was 8 years. Disease-free survival was analyzed using univariate and multivariate analyses. Based on this we proposed and tested a new TNM system against the 2002 TNM version.

RESULTS

Tumor recurrence was diagnosed in 48 patients (20.2%) at a median of 21.5 months. Diameter based analysis of stage T3a revealed that this was an inhomogeneous group that included patients with small tumors and an excellent prognosis along with patients with large tumors and a poor prognosis. Based on this information we initiated a modified TNM staging system that ignores perinephric fat invasion. In the proposed staging system stage T1a includes tumors 4 cm or less and stage T1b includes tumors more than 4 but 7 cm or less. Stage T2 is divided into T2a-tumors greater than 7 but 10 cm or less and T2b-tumors greater than 10 cm. Stage T3a is reserved for renal vein tumor invasion. The proposed TNM performed better than the 2002 version using the Nagelkerke R(2) test (0.439 vs 0.359), and the Hosmer and Lemeshow test (0.335 vs 0.191).

CONCLUSIONS

The current definition of stage T3a renal cell carcinoma embraces an inhomogeneous group of patients with marked differences in prognosis. We believe that tumor invasion into the perinephric fat does not necessarily predict aggressive biological behavior.

Concurrent angiomyolipoma and two oncocytomas in the same kidney

We report on a rare case of synchronous angiomyolipoma (AML) and 2 oncocytomas (OCs) in the same kidney of a 73-year-old woman. During the course of a follow-up for a long-standing staghorn calculus in the left kidney, a 4-cm right suprarenal mass and a small solid nodule adjacent to a cyst in the midportion of the right kidney were radiographically discovered. A radical nephrectomy was performed. The suprarenal tumor was found to be an AML, and the small nodule was an OC (1.5 cm). An additional OC (0.8 cm) elsewhere in the right kidney was also identified. The coexistence of AML and other renal tumors is uncommon. Among reported cases, conventional renal cell carcinoma, possibly reflecting its higher incidence, has been the most common concurrent tumor with AML. Although only rare cases of simultaneous AML and OC have been reported in the literature, it appears that the proportion of OC among concurrent renal tumors with AML is higher than expected based on its frequency among all surgically resected renal neoplasms. Whether there is a pathogenetic association between AML and OC needs to be further investigated.

High Incidence of Chromosome 1 Abnormalities in a Series of 27 Renal Oncocytomas: Cytogenetic and Fluorescence In Situ Hybridization Studies

Context.—It has recently been shown by cytogenetics that there is a high incidence of chromosome 1 abnormalities in renal oncocytomas.

Objective.—To confirm the cytogenetic results by fluorescence in situ hybridization (FISH) analysis.

Design.—Nine additional cytogenetic analyses were added to those reported in our recent study, with a total of 27 tumors studied, which makes it the largest series of renal oncocytomas studied to date by cytogenetics and/or FISH. We used the LSI 1p36/LSI 1q25 Dual Color Probe Set to make the analyses.

Results.—In this study, combined cytogenetics and FISH showed loss of chromosome arm 1p1 in 48% of renal oncocytomas. By FISH, deletion of 1p36.3 was observed in 59% of renal oncocytomas, whereas by cytogenetics, abnormality in chromosome 1 was seen in 32% of tumors. However, the incidence of chromosome 1 abnormalities among 9 bilateral tumors was much higher than in single tumors (88% vs 28%, respectively). Loss of only the 1p36.3 site occurred in 2 renal oncocytomas with translocation of chromosome 1, as shown by cytogenetics. Concordance between the 2 techniques, when they were used simultaneously to detect chromosome 1p1 abnormality, was 82%.

Conclusions.—This study further confirmed our prior results demonstrating the widespread occurrence of chromosome 1 abnormalities in renal oncocytomas. Although no abnormalities in chromosome 1 in tumors with normal karyotypes were detected by FISH using the current set of probes, a much higher incidence of such abnormalities was found in bilateral tumors, suggesting that genetic alterations related to the development of renal oncocytoma reside in this region.