Renal oncocytoma with t(5;12;11), der(1)1;8) and add(19): "true" oncocytoma or chromophobe adenoma?

Cytogenetic analysis of 130 renal oncocytomas identify three distinct and mutually exclusive diagnostic classes of chromosome aberrations

The cytogenetic alterations in renal oncocytoma (RO) are poorly understood. We analyzed 130 consecutive RO for karyotypic alterations. Clonal chromosome abnormalities were identified in 63 (49%) cases, which could be categorized into three classes of mutually exclusive cytogenetic categories. Class 1 (N = 20) RO had diploid karyotypes with characteristic 11q13 rearrangement in balanced translocations with 10 or more different chromosome partners in all cases. We identified recurrent translocation partners at 5q35, 6p21, 9p24, 11p13-14, and 11q23, and confirmed that CCND1 gene rearrangement at 11q13 utilizing fluorescence in situ hybridization (FISH). Class 2 RO (N = 25) exhibited hypodiploid karyotypes with loss of chromosome 1 and/or losses of Y in males and X in females in all cases. The class 3 tumors comprising of 18 cases showed diverse types of abnormalities with the involvement of two or more chromosomes exclusive of abnormalities seen in classes 1 and 2 tumors. Furthermore, karyotypically uninformative cases were subjected to FISH analysis to identify classes 1 and 2 abnormalities. In this group, we found similar frequencies of CCND1 rearrangement, loss of chromosome 1 or Y as with karyotypically abnormal cases. We validated our results against 91 tumors from the Mitelman database. Correlation of clinical data with all the three classes of ROs showed no clear evidence of overall patient survival. Our findings support the hypothesis that RO exhibit three principal cytogenetic categories, which may have different roles in initiation and/or progression. These cytogenetic markers provide a key tool in the diagnostic evaluation of RO.

Liver Metastases From Renal Oncocytoma With Vascular Extension

The 2016 World Health Organization Renal Tumor Classification defines renal oncocytoma (RO) as a benign epithelial tumor; however, malignant histopathologic features have been documented. Rare cases with metastases have been reported. We describe the case of a 62-year-old woman who was referred to the Urology Clinic for a routine work-up. Magnetic resonance imaging and computerized tomography showed a 7-cm mass in the middle and lower portions of the left kidney and 2 suspected liver metastases. The patient underwent surgery. Microscopically both renal and liver lesions presented solid, solid-nested, and microcystic architecture, composed predominantly of large eosinophilic cells without any worrisome pattern except the vascular extension. The cells were positive for S100A1, CD117, and PAX-8 and negative for CAIX, CK7, and AMACR. Fluorescence in situ hybridization showed a disomic profile for the chromosomes 1, 2, 6, 7, 10, 17. No mutation of coding sequence of the SDHB, SDHC, SDHD, VHL, and BHD genes and no loss of heterozygosity at 3p were found. The final diagnosis was "RO" according to the 2016 World Health Organization Renal Tumor Classification with "liver metastases." This report provides a wide clinical-pathologic, immunophenotypical and molecular documentation of a RO with liver metastases.

Genetic and Chromosomal Aberrations and Their Clinical Significance in Renal Neoplasms

The most common form of malignant renal neoplasms is renal cell carcinoma (RCC), which is classified into several different subtypes based on the histomorphological features. However, overlaps in these characteristics may present difficulties in the accurate diagnosis of these subtypes, which have different clinical outcomes. Genomic and molecular studies have revealed unique genetic aberrations in each subtype. Knowledge of these genetic changes in hereditary and sporadic renal neoplasms has given an insight into the various proteins and signalling pathways involved in tumour formation and progression. In this review, the genetic aberrations characteristic to each renal neoplasm subtype are evaluated along with the associated protein products and affected pathways. The potential applications of these genetic aberrations and proteins as diagnostic tools, prognostic markers, or therapeutic targets are also assessed.

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.

Vimentin reactivity in renal oncocytoma: immunohistochemical study of 234 cases

CONTEXT

The expression of vimentin in benign renal oncocytomas has been controversial. However, this is of clinical significance because immunostains may be used in differential diagnosis of renal tumors on limited biopsy specimens. Using different staining and analysis methods, we studied vimentin immunoreactivity in a large series of renal oncocytomas with a special emphasis on the immunoreactivity patterns.

OBJECTIVE

Immunohistochemical expression of vimentin has been used in the differential diagnosis of renal epithelial neoplasms. Although typically expressed in most renal cell carcinomas, the immunoreactivity of this intermediate filament in renal oncocytomas has been controversial.

DESIGN

We studied vimentin immunoreactivity in a large series of 234 renal oncocytomas using 2 staining methods as well as manual and automated imaging analyses.

RESULTS

We found that the focal vimentin immunoreactivity can be seen in most (72.6%) renal oncocytomas with vimentin-positive tumor cells usually found in the edge of a central scar or in small clusters scattered throughout the tumor. Computer-aided imaging analysis using ChromaVision Automatic Cellular Imaging System II confirmed the difference in vimentin immunoreactivity between oncocytoma and other renal neoplasms.

CONCLUSIONS

Our study of vimentin immunohistochemistry in a series of renal oncocytomas, which to our knowledge is the largest ever published, showed focal vimentin positivity detected in most oncocytomas. Because the vimentin staining patterns in renal oncocytomas are different from those seen in clear cell or papillary renal cell carcinomas, we consider vimentin staining to be helpful in the differential diagnosis of oncocytoma from other renal tumor mimics. Furthermore, strong vimentin positivity in a renal cell neoplasm does not exclude the diagnosis of renal oncocytoma, particularly in a limited biopsy specimen.

Insertion (8;11) in a renal oncocytoma with multifocal transformation to chromophobe renal cell carcinoma

We report the case of a 43-year-old male with multiple tumor foci showing microscopic features of chromophobe renal carcinoma (ChRCC) arising in an oncocytoma. Conventional cytogenetics of fresh tumor cells and fluorescence in situ hybridization (FISH) revealed the following abnormal karyotype: 46,XY,der(8)ins(8;11)(p?;q13),der(11)ins(8;11)inv(11)(q12?p15) with CCND1 (11q13) rearrangement. To our knowledge, chromosome 8 has not been reported as a partner involved in structural rearrangements of 11q13 in oncocytomas. FISH in paraffin tissue sections revealed a rearrangement of CCND1 (11q13) in the oncocytoma cells. The multiple foci of chromophobe carcinoma presented multiple copies of CCND1, suggesting that they represented a transformation from oncocytoma into ChRCC. There was immunohistochemical overexpression of CCND1 in both oncocytoma and chromophobe carcinoma cells. In this case, the correlation of the microscopic findings with changes in CCND1 gene associated to CCND1 overexpression in both components suggest that the ChRCC would have originated from the preexisting oncocytoma. It is not possible to detect, by cytogenetic techniques alone, if the ChRCC component have also the CCND1 rearrangement in addition to the detected polysomy. FISH techniques on paraffin tissue sections may help to identify genetic aberrations such as CCND1 rearrangement in order to establish a diagnosis of oncocytoma.

Losses of 1p and chromosome 14 in renal oncocytomas

We performed cytogenetic analyses of 8 renal oncocytomas to identify chromosomal regions involved in the tumorigenesis of oncocytomas. All cases showed chromosomal findings corresponding to established cytogenetic subsets of renal oncocytomas: 3 cases with normal karyotypes, 1 case with rearrangement of 11q, and 4 cases with losses of chromosome 14. In the latter cytogenetic subgroup, monosomy 14 was additionally accompanied by either monosomy 1 in 2 cases or loss of 1p in a third case, providing insights in the cytogenetic evolution of this subgroup.

Oncocytic renal neoplasms: diagnostic considerations

Advances in our understanding of renal neoplasia have resulted in recognition of numerous tumors that are composed predominantly of cells with abundant eosinophilic cytoplasm. This article discusses the features of renal oncocytoma (including oncocytosis), chromophobe renal cell carcinoma (RCC), and clear cell RCC; explores the relationship between renal oncocytoma and chromophobe RCC; briefly discusses other tumors with abundant eosinophilic cytoplasm; and emphasizes the differential diagnosis of such tumors.

Hybrid chromophobe renal cell neoplasm

Hybrid renal cell neoplasms (HRCNs) containing areas of tumor cells displaying cytological features of chromophobe renal cell carcinoma (CHRCC) and renal oncocytoma (RO) have been recently described in patients with renal oncocytosis and Birt-Hogg-Dube (BHD) syndrome (autosomal dominant genodermatosis). In this study, we identified cases of sporadic HRCN. We reviewed 425 consecutive renal cell carcinomas (RCC), 18 CHRCC, six HRCN, and 25 RO. Five HRCN were identified, including four from the group of RCC and two from RO. Patient age ranged from 40 to 68 years (mean age: 54 years), and the male:female ratio was 4:1. Tumors measured from 1.8 to 5 cm (mean diameter: 3.0 cm). Tumoral necrosis was not seen. Vascular invasion into medium-sized veins was identified in one HRCN. Chromophobe cells accounted for 20-80% of the tumors. Hale's colloidal stain showed weak to moderate diffuse cytoplasmic staining in scattered cells corresponding to those displaying routine staining features of chromophobe cells. Areas of oncocytic cells in studied tumors and control oncocytomas showed negative or focal cytoplasmic staining usually bordering extra- or intra-cytoplasmic lumina. Immunostaining for cytokeratin 7 and vimentin showed focal immunoreactivity in three cases and negative reactivity in all six cases, respectively. None of the study cases had microscopic RO, as commonly seen in renal oncocytosis, or were associated with BHD syndrome Sporadic HRCN accounted for 1% of RCC. They were of smaller size than RCC and were associated with a favorable prognosis.

Eosinophilic and classic chromophobe renal cell carcinomas have similar frequent losses of multiple chromosomes from among chromosomes 1, 2, 6, 10, and 17, and this pattern of genetic abnormality is not present in renal oncocytoma

That chromophobe renal cell carcinoma has an uncommon eosinophilic variant has been recognized for more than a decade. In sections stained with hematoxylin and eosin, the eosinophilic variant of chromophobe renal cell carcinoma and renal oncocytoma are similar in appearance. While it is well established that chromophobe renal cell carcinoma and renal oncocytoma have different patterns of genetic anomalies, little is known of the genetics of the eosinophilic variant of chromophobe renal cell carcinoma. This study was undertaken to elucidate the genetic lesions of eosinophilic chromophobe renal cell carcinoma and to compare them with those found in classic chromophobe renal cell carcinoma and in renal oncocytoma. A total of 29 renal neoplasms--nine eosinophilic chromophobe renal cell carcinomas, 10 classic chromophobe renal cell carcinomas, and 10 oncocytomas--were investigated by fluorescence in situ hybridization on 5 microm paraffin-embedded tissue sections with centromeric probes for chromosomes 1, 2, 6, 10, and 17. Signals were counted in 100-200 neoplastic nuclei from each tumor. Chromophobe renal cell carcinomas frequently showed loss of chromosomes 1 (70% of classic, 67% of eosinophilic), 2 (90% classic, 56% eosinophilic), 6 (80% classic, 56% eosinophilic), 10 (60% classic, 44% eosinophilic), and 17 (90% classic, 78% eosinophilic); Among the classic chromophobe renal cell carcinomas, only one had no loss of any of the chromosomes, while 50% had loss of all five chromosomes. Among the eosinophilic chromophobe renal cell carcinomas, one of nine had no loss and 44% had loss of all five chromosomes. One oncocytoma had loss of chromosome 1. No other chromosomal loss was detected in the oncocytomas. In conclusion, losses of chromosomes 1, 2, 6, 10, and 17 are frequent in both eosinophilic and classic chromophobe renal cell carcinomas. Loss of chromosome 1 occurs occasionally in oncocytoma but losses of chromosomes 2, 6, 10, and 17 are not found in oncocytomas. When the differential diagnostic problem is oncocytoma vs eosinophilic chromophobe renal cell carcinoma, detection of losses of chromosomes 2, 6, 10, or 17 effectively excludes the diagnosis of oncocytoma and supports the diagnosis of chromophobe renal cell carcinoma.

The genetics of renal oncocytosis: a possible modelfor neoplastic progression

Renal oncocytosis is a rare condition characterized by the presence of numerous oncocytomas and oncocytic changes in the renal tubules. Other than oncocytomas associated with the Birt-Hogg-Dube (BDH) syndrome, the genetics of oncocytosis is not known. Whether oncocytomas and oncocytosis are similar to BDH syndrome, in which the tumors diploid (as most oncocytomas are), or show chromosomal losses may be significant regarding the observation that in oncocytosis, there frequently is morphological evidence of progression to chromophobe carcinoma. Here we report on the case of a 69-year old male who underwent a staged procedure of partial nephrectomy on the left side and right radical nephrectomy for multiple renal tumors. The tumors were studied by routine hematoxylin and eosin morphology, immunohistochemistry, cytogenetics, and loss of heterozygosity analysis. Both kidneys had numerous oncocytic neoplasms morphologically progressing from oncocytomas to hybrid tumors with chromophobe carcinoma. Genetic studies demonstrated progression from normal cytogenetics to chromosomal losses similar to those in some oncocytomas and in chromophobe carcinomas. The genetics of this apparently nonfamilial oncocytoma differs from that of BDH syndrome and is characterized by losses involving chromosomes 1, 14, 21, and Y. To our knowledge, this is the first report of the genetic and cytogenetic findings in oncocytosis not related to BDH syndrome and may suggest a possible model of progression from oncocytoma to chromophobe renal cell carcinoma.

Renal oncocytomas with 11q13 rearrangements: cytogenetic, molecular, and immunohistochemical analysis of cyclin D1

Two groups of renal oncocytomas have been cytogenetically defined by the loss of one or both of chromosomes Y and 1 or by structural rearrangement involving 11q12~q13. We report five renal oncocytomas with structural chromosomal rearrangements involving 11q13 with previously unreported partner chromosomes (namely, 1, 6, and 7). For two of the five cases, a t(6;11)(p21;q13) translocation was revealed; the others had t(1;11)(p13;q13), t(7;11)(q11.2;q13), and t(5;11)(q35; q13). Fluorescence in situ hybridization confirmed translocation of CCND1 at 11q13 to partner chromosomes 5, 6, and 7. Overexpression of cyclin D1, the protein product of CCND1, was detected in three of the five cases (60%) by means of immunohistochemical staining of formalin-fixed, paraffin-embedded tumor sections. In three cases for which fresh tissue was available, Southern blot analysis using the MDL-5 probe for the BCL1 breakpoint did not reveal rearrangement of BCL1. In addition, six consecutive renal oncocytomas diagnosed at our institution between 1999 and 2002 whose karyotypes did not show 11q13 translocations were all negative for cyclin D1 overexpression under immunohistochemical analysis. The findings of CCND1 rearrangement with FISH and correlation with cyclin D1 overexpression under immunohistochemical analysis suggest that cyclin D1 alterations play a role in the subset of renal oncocytomas with 11q translocations, although other genes may also be involved.

Renal oncocytomas with rearrangements involving 11q13 contain breakpoints near CCND1

Oncocytomas are typically benign epithelial tumors whose predominant feature is a massive accumulation of mitochondria in the cytoplasm. With the goal of identifying genes controlling mitochondrial proliferation, we studied three oncocytomas belonging to the cytogenetic subgroup with 11q13 rearrangements. Fluorescence in situ hybridization using bacterial artificial chromosome (BAC) clones showed that the 11q13 breakpoints in all three tumors were near the CCND1 (previously BCL1) gene and did not disrupt any other known gene. The rearrangement in one tumor consisted of a segmental duplication that included 11q13, suggesting that known mitochondrially targeted genes immediately distal to CCND1 may be involved in oncocytic proliferation.

Cytogenetic Analysis of a Series of 13 Renal Oncocytomas

PURPOSE

Only about 50 renal oncocytomas have been studied cytogenetically. They fall into 3 categories, namely 1-normal karyotype, 2-monosomy 1, often with Y chromosome loss, and 3-structural abnormalities of 11q13. Additional abnormalities may occur with transformation to chromophobe renal cell carcinoma, although exactly which one is unclear. We expanded the oncocytoma data base to shed light on changes that characterize transformation.

MATERIALS AND METHODS

A total of 14 oncocytomas from 12 patients were collected in 2(1/2) years. One tumor failed to grow but 13 were successfully karyotyped.

RESULTS

Seven tumors (53.8%), including 2 from 1 kidney, had normal karyotypes or abnormalities characteristic of normal kidney tissue. A total of 6 tumors from 5 individuals (46.2%) had chromosome 1 abnormalities. Monosomy 1 was detected in 2 single tumors and in both tumors in a bilateral case. Structural anomalies resulting in loss of the short arm of chromosome 1 were found in an additional 2 patients. Other abnormalities, including Y chromosome loss and monosomy 14, were observed but no abnormalities of 11q13 were seen.

CONCLUSIONS

Our series confirms that 1p loss is the most common anomaly in oncocytoma. Additional studies are required to understand the transformation potential of this usually benign tumor, identify the putative 1p tumor suppressor gene and determine whether karyotypically normal tumors have molecular abnormalities of 1p.

Renal cancer: cytogenetic and molecular genetic aspects

To date, much progress has been made in the fields of cytogenetics and molecular genetics of renal tumors. The previous and recent findings have delineated the characteristics of the various tumors, particularly the cytogenetic and molecular differences that exist between papillary and nonpapillary clear cell renal cell carcinomas (RCCs). At the same time, new cytogenetic subtypes have emerged [e.g., t(X;1)] in subtypes of RCC, while in others (e.g., Wilms tumors) several new cytogenetic abnormalities and consequent molecular involvement have been found. In addition to Wilms tumor, papillary RCC, and clear-cell RCC, cytogenetic and fluorescence in situ hybridization analyses have been performed on several other tumors of the kidney, including chromophobic carcinoma, metanephric adenoma, collecting duct carcinoma, transitional cell carcinoma, congenital mesoblastic nephroma, and malignant rhabdoid tumors of the kidney. This review is therefore intended to present a concise update on the cytogenetic and molecular data on renal tumors, focusing mainly on the clinical usefulness of the findings reported in the literature.

Renal cell carcinoma as a secondary malignancy after treatment of acute promyelocytic leukemia

Numerous children have been treated successfully for cancer and are surviving into adulthood. As this population has aged, an increasing number of secondary malignancies has emerged. Renal cell carcinoma (RCC) is a rare tumor in childhood and has not been documented previously to occur after treatment of acute promyelocytic leukemia (APL). This report describes the clinical course of APL treated in a child in whom RCC subsequently developed during adolescence approximately 5 years after therapy.

Parvalbumin is constantly expressed in chromophobe renal carcinoma

Chromophobe renal carcinoma is composed of neoplastic cell showing several features similar to those found in the intercalated cells of the collecting ducts. Because the distal nephron expresses calcium-binding proteins playing a role in calcium homeostasis, we reasoned that these proteins could be expressed by chromophobe carcinoma and therefore represent a diagnostic marker. We studied the immunohistochemical expression of different calcium-binding proteins (parvalbumin, calbindin-D28K, and calretinin) in 140 renal tumors, including 75 conventional (clear cell) carcinomas, 32 chromophobe carcinomas, 17 papillary renal cell carcinomas, and 16 oncocytomas. Parvalbumin was strongly positive in all primary chromophobe carcinomas and in one pancreatic metastasis; it was positive in 11 of 16 oncocytomas and absent in conventional (clear cell) and papillary renal cell carcinomas, either primary or metastatic. Calbindin-D28K and calretinin were negative in all tumors, with the exception of two chromophobe carcinomas, four oncocytomas, and two papillary renal cell carcinomas showing inconspicuous calretinin expression. Our data demonstrate that parvalbumin may be a suitable marker for distinguishing primary and metastatic chromophobe carcinoma from conventional (clear cell) and papillary renal cell carcinoma. Moreover, they suggest a relationship between chromophobe renal carcinoma and renal oncocytoma and indicate that chromophobe carcinoma exhibits differentiation toward the collecting-duct phenotype.

Expression profiling of renal epithelial neoplasms: a method for tumor classification and discovery of diagnostic molecular markers

The expression patterns of 7075 genes were analyzed in four conventional (clear cell) renal cell carcinomas (RCC), one chromophobe RCC, and two oncocytomas using cDNA microarrays. Expression profiles were compared among tumors using various clustering algorithms, thereby separating the tumors into two categories consistent with corresponding histopathological diagnoses. Specifically, conventional RCCs were distinguished from chromophobe RCC/oncocytomas based on large-scale gene expression patterns. Chromophobe RCC/oncocytomas displayed similar expression profiles, including genes involved with oxidative phosphorylation and genes expressed normally by distal nephron, consistent with the mitochondrion-rich morphology of these tumors and the theory that both lesions are related histogenetically to distal nephron epithelium. Conventional RCCs underexpressed mitochondrial and distal nephron genes, and were further distinguished from chromophobe RCC/oncocytomas by overexpression of vimentin and class II major histocompatibility complex-related molecules. Novel, tumor-specific expression of four genes-vimentin, class II major histocompatibility complex-associated invariant chain (CD74), parvalbumin, and galectin-3-was confirmed in an independent tumor series by immunohistochemistry. Vimentin was a sensitive, specific marker for conventional RCCs, and parvalbumin was detected primarily in chromophobe RCC/oncocytomas. In conclusion, histopathological subtypes of renal epithelial neoplasia were characterized by distinct patterns of gene expression. Expression patterns were useful for identifying novel molecular markers with potential diagnostic utility.

Concurrent angiomyolipoma and renal cell neoplasia: a study of 36 cases

Little is known about the association of angiomyolipoma and adult renal-cell neoplasia. We studied the clinicopathologic features of 36 patients with concurrent angiomyolipoma and renal-cell neoplasia from the consultation and surgical pathology files of nine institutions. HMB-45 immunoreactivity was analyzed in both neoplasms. Twenty-five sporadic cases of patients with angiomyolipoma and renal-cell neoplasia and 11 cases of patients with tuberous sclerosis, as defined by Gomez' criteria, had mean ages of 59 and 53 years, respectively, and female-male ratios of 2:1 and 5:1, respectively. The mean size of the angiomyolipomas was 1 cm in the sporadic cases and 3 cm in those patients with tuberous sclerosis (medians: 0.5 and 3 cm, respectively, P =.002). The mean sizes of the renal-cell neoplasms were 5 cm in sporadic cases and 6 cm in patients with tuberous sclerosis (medians: 4 and 5 cm, respectively; P =.88). In both clinical settings, angiomyolipoma was more commonly the incidental tumor. Clear-cell (conventional) renal-cell carcinoma was the most common renal-cell neoplasm in both groups of patients, accounting for approximately two thirds of the tumors. In patients with tuberous sclerosis, 27% of renal-cell neoplasms were oncocytomas, compared with 8% in sporadic cases (P =.15). Papillary neoplasia, chromophobe, and collecting-duct renal-cell carcinoma were found only in sporadic cases. All of the 22 renal-cell neoplasms studied were negative for HMB-45, whereas all 25 angiomyolipomas studied were positive.

Ultrastructural observations on mitochondria and microvesicles in renal oncocytoma, chromophobe renal cell carcinoma, and eosinophilic variant of conventional (clear cell) renal cell carcinoma

On light microscopic examination, the morphologically overlapping features of granular eosinophilic cytoplasm in renal oncocytoma and the eosinophilic variants of chromophobe renal cell carcinoma and conventional (clear cell) renal cell carcinoma may pose difficulties in diagnosis. We investigated the ultrastructure of 5 renal oncocytomas, 7 eosinophilic variants of chromophobe renal cell carcinoma, and 5 eosinophilic variants of conventional (clear cell) renal cell carcinoma. Special attention was paid to mitochondria and microvesicles and interrelations thereof. The electron microscopic features were correlated with the light microscopic findings. All of the tumors had abundant mitochondria. Although abundant microvesicles were present in all of the chromophobe renal cell carcinomas, scant numbers of microvesicles were also sometimes present in renal oncocytomas (2 of 5) and in the eosinophilic variant of conventional (clear cell) renal cell carcinoma (1 of 5). The mitochondria in all three types of renal neoplasms studied differed in morphology, being predominantly uniform and round with predominantly lamellar cristae in renal oncocytoma, variable in shape and size with predominantly tubulocystic cristae in chromophobe renal cell carcinoma, and swollen and pleomorphic with rarefied matrix and attenuated cristae in the eosinophilic variant of conventional (clear cell) renal cell carcinoma. Variable numbers of mitochondria in all of the chromophobe renal cell carcinomas had outpouchings of the outer membranes, some of which carried parts of inner membrane within them. These outpouchings closely resembled the nearby cytoplasmic microvesicles, as did the tubulocystic cristae of the mitochondria. Some microvesicles contained homogeneous, electron-dense, finely granular matrix, similar to that seen in mitochondria. In one of seven chromophobe renal cell carcinomas, microvesicles were present in rough endoplasmic reticulum, and in two others, mitochondria were present within some vesicles. These features strongly suggest a close relationship between the microvesicles and mitochondria. Based on the role of vesicle formation in normal mitochondriogenesis, and some of our observations, we propose that defective mitochondriogenesis may be the source of microvesicles in chromophobe renal cell carcinomas.

Construction of a 350-kb sequence-ready 11q13 cosmid contig encompassing the markers D11S4933 and D11S546: mapping of 11 genes and 3 tumor-associated translocation breakpoints

Previously, we located three novel human tumor-associated translocation breakpoints in the chromosome 11q13 region between the markers D11S4933 and D11S546. To facilitate the molecular analysis of these breakpoints, we have constructed a continuous sequence-ready cosmid and PAC contig of approximately 350 kb, including the markers D11S4933 and D11S546. In addition, a detailed transcript map was generated. This resulted in the precise positioning of 11 genes and ESTs within the contig, including 4 genes already known to map in the 11q13 region. Three other genes that we positioned within the contig showed homologies to unmapped genes from human and/or other species. Three ESTs were novel. Partial cosmid sequencing resulted in the establishment of the direction of transcription of several of the reported genes. This contig will be instrumental for the detailed characterization of the tumor-associated chromosomal breakpoints and the identification of other 11q13-associated disease genes.

Renal oncocytosis: a morphologic study of fourteen cases

Diffuse renal involvement by numerous oncocytic nodules has rarely been described. We report 14 cases (19 specimens) with innumerable oncocytic nodules in the kidney. Invariably, these kidneys showed additional associated findings. We suggest the term renal oncocytosis for this entire morphologic spectrum. Six (43%) cases had histologically or radiologically proven bilateral involvement. Each specimen had at least one dominant tumor (2.0-10.5 cm) in addition to numerous other microscopic to macroscopic oncocytic nodules. Additional features observed were: interstitial pattern, with the oncocytic tubules and acini diffusely intermingling with and infiltrating between non-neoplastic parenchyma (one case); diffuse oncocytic change in the nonneoplastic tubules, cytologically difficult to separate from the oncocytic nodules (seven cases); and benign oncocytic cortical cysts (four cases). The dominant mass in 13 specimens was a renal oncocytoma and in two, a chromophobe renal cell carcinoma. In four specimens, the largest tumor was considered a hybrid tumor because of the presence of mixed histologic features of both tumor types. Most smaller nodules had the morphologic features of renal oncocytoma, but a few had the appearance of chromophobe renal cell carcinoma or nodules with hybrid features. We conclude that the presence of numerous oncocytic nodules may be associated with a wide spectrum of oncocytic changes in the kidney. The association of numerous renal oncocytoma-like nodules with lesions having a mixed morphology or a morphology of pure chromophobe renal cell carcinoma suggests that they may constitute a morphologic spectrum of oncocytic tumors and that renal oncocytoma and chromophobe renal cell carcinoma may arise from a common progenitor lesion.