Translocation (X;1) reveals metastasis 31 years after renal cell carcinoma

Pediatric Renal Tumors: Updates in the Molecular Era

Molecular characterization has led to advances in the understanding of pediatric renal tumors, including the association of pediatric cystic nephromas with DICER1 tumor syndrome, the metanephric family of tumors with somatic BRAF mutations, the characterization of ETV6-NTRK3-negative congenital mesoblastic nephromas, the expanded spectrum of gene fusions in translocation renal cell carcinoma, the relationship of clear cell sarcoma of the kidney with other BCOR-altered tumors, and the pathways affected by SMARCB1 alterations in rhabdoid tumors of the kidney. These advances have implications for diagnosis, classification, and treatment of pediatric renal tumors.

Clinicopathological Findings on 28 Cases with XP11.2 Renal Cell Carcinoma

Xp11.2 translocation carcinoma is a distinct subtype of renal cell carcinoma characterized by translocations involving the TFE3 gene. Our study included the morphological, immunohistochemical and clinicopathological examination of 28 Xp11.2 RCCs. The immunophenotype has been assessed by using CA9, CK7, CD10, AMACR, MelanA, HMB45, Cathepsin K and TFE3 immunostainings. The diagnosis was confirmed by TFE3 break-apart FISH in 25 cases. The ages of 13 male and 15 female patients, without underlying renal disease or having undergone chemotherapy ranged from 8 to 72. The mean size of the tumors was 78.5 mm. Forty-three percent of patients were diagnosed in the pT3/pT4 stage with distant metastasis in 6 cases. Histological appearance was branching-papillary composed of clear cells with voluminous cytoplasm in 13 and variable in 15 cases, including one tumor with anaplastic carcinoma and another with rhabdoid morphology. Three tumors were labeled with CA9, while CK7 was negative in all cases. Diffuse CD10 reaction was observed in 17 tumors and diffuse AMACR positivity was described in 14 tumors. The expression of melanocytic markers and Cathepsin K were seen only in 7 and 6 cases, respectively. TFE3 immunohistochemistry displayed a positive reaction in 26/28 samples. TFE3 rearrangement was detected in all the analyzed cases (25/25), including one with the loss of the entire labeled break-point region. The follow-up time ranged from 2 to 300 months, with 7 cancer-related deaths. In summary, Xp11.2 carcinoma is an uncommon form of renal cell carcinoma with a variable histomorphology and rather aggressive clinical course.

Clinical heterogeneity of Xp11 translocation renal cell carcinoma: impact of fusion subtype, age, and stage

Xp11 translocation renal cell carcinomas harbor chromosome translocations involving the Xp11 breakpoint, resulting in gene fusions involving the TFE3 gene. The most common subtypes are the ASPSCR1-TFE3 renal cell carcinomas resulting from t(X;17)(p11;q25) translocation, and the PRCC-TFE3 renal cell carcinomas, resulting from t(X;1)(p11;q21) translocation. A formal clinical comparison of these two subtypes of Xp11 translocation renal cell carcinomas has not been performed. We report one new genetically confirmed Xp11 translocation renal cell carcinoma of each type. We also reviewed the literature for all published cases of ASPSCR1-TFE3 and PRCC-TFE3 renal cell carcinomas and contacted all corresponding authors to obtain or update the published follow-up information. Study of two new, unpublished cases, and review of the literature revealed that 8/8 patients who presented with distant metastasis had ASPSCR1-TFE3 renal cell carcinomas, and all but one of these patients either died of disease or had progressive disease. Regional lymph nodes were involved by metastasis in 24 of the 32 ASPSCR1-TFE3 cases in which nodes were resected, compared with 5 of 14 PRCC-TFE3 cases (P=0.02).; however, 11 of 13 evaluable patients with ASPSCR1-TFE3 renal cell carcinomas who presented with N1M0 disease remained disease free. Two PRCC-TFE3 renal cell carcinomas recurred late (at 20 and 30 years, respectively). In multivariate analysis, only older age or advanced stage at presentation (not fusion subtype) predicted death. In conclusion, ASPSCR1-TFE3 renal cell carcinomas are more likely to present at advanced stage (particularly node-positive disease) than are PRCC-TFE3 renal cell carcinomas. Although systemic metastases portend a grim prognosis, regional lymph node involvement does not, at least in short-term follow-up. The tendency for PRCC-TFE3 renal cell carcinomas to recur late warrants long-term follow-up.

Molecular cytogenetic analysis for TFE3 rearrangement in Xp11.2 renal cell carcinoma and alveolar soft part sarcoma: validation and clinical experience with 75 cases

Renal cell carcinoma with TFE3 rearrangement at Xp11.2 is a distinct subtype manifesting an indolent clinical course in children, with recent reports suggesting a more aggressive entity in adults. This subtype is morphologically heterogeneous and can be misclassified as clear cell or papillary renal cell carcinoma. TFE3 is also rearranged in alveolar soft part sarcoma. To aid in diagnosis, a break-apart strategy fluorescence in situ hybridization (FISH) probe set specific for TFE3 rearrangement and a reflex dual-color, single-fusion strategy probe set involving the most common TFE3 partner gene, ASPSCR1, were validated on formalin-fixed, paraffin-embedded tissues from nine alveolar soft part sarcoma, two suspected Xp11.2 renal cell carcinoma, and nine tumors in the differential diagnosis. The impact of tissue cut artifact was reduced through inclusion of a chromosome X centromere control probe. Analysis of the UOK-109 renal carcinoma cell line confirmed the break-apart TFE3 probe set can distinguish the subtle TFE3/NONO fusion-associated inversion of chromosome X. Subsequent extensive clinical experience was gained through analysis of 75 cases with an indication of Xp11.2 renal cell carcinoma (n=54), alveolar soft part sarcoma (n=13), perivascular epithelioid cell neoplasms (n=2), chordoma (n=1), or unspecified (n=5). We observed balanced and unbalanced chromosome X;17 translocations in both Xp11.2 renal cell carcinoma and alveolar soft part sarcoma, supporting a preference but not a necessity for the translocation to be balanced in the carcinoma and unbalanced in the sarcoma. We further demonstrate the unbalanced separation is atypical, with TFE3/ASPSCR1 fusion and loss of the derivative X chromosome but also an unanticipated normal X chromosome gain in both males and females. Other diverse sex chromosome copy number combinations were observed. Our TFE3 FISH assay is a useful adjunct to morphologic analysis of such challenging cases and will be applicable to assess the growing spectrum of TFE3-rearranged tumors.

Uncommon and recently described renal carcinomas

Major consensus conferences held over a decade ago laid the foundations for the current (2004) WHO classification of renal carcinoma. Clear cell, papillary and chromophobe carcinomas account for 85-90% carcinomas seen in routine practice. The remaining 10-15% of carcinomas consist of rare sporadic and hereditary tumors, some of which had been long recognized, but many of which only emerged as distinct entities in the decade leading up to the WHO publication. Collecting-duct carcinoma is a rare, often lethal form of carcinoma. Medullary carcinoma associated with sickle cell trait, has emerged as a distinctive tumor showing some overlapping features with upper tract urothelial carcinoma. Mucinous tubular and spindle-cell carcinoma and tubulocystic carcinoma were earlier considered as patterns of low-grade collecting-duct carcinoma, but are now recognized as separate tumor entities. Carcinomas associated with somatic translocations of TFE3 and TFEB comprise a significant proportion of pediatric renal carcinomas. Oncocytoid renal carcinomas in neuroblastoma survivors was recognized as a unique tumor category in the WHO classification. Renal carcinoma associated with end-stage renal disease is now recognized as having distinct morphological patterns and behavior. In addition there is a group of rare recently described carcinomas, including clear cell papillary carcinoma, oncocytic papillary renal cell carcinoma, follicular renal carcinoma and leiomyomatous renal cell carcinoma. It behooves the surgical pathologist to not only be capable of diagnosing the common forms of renal cancer, but also to be aware of the rare types of renal carcinoma, many of which have emerged in recent years.

Xp11.2 translocation renal cell carcinoma occurring during pregnancy with a novel translocation involving chromosome 19: a case report with review of the literature

The recently recognized renal cell carcinomas (RCCs) associated with Xp11.2 translocations (TFE3 transcription factor gene fusions) are rare tumors predominantly reported in children. They comprise at least one-third of pediatric RCCs and only few adult cases have been reported. Here, we present a case of Xp11.2 translocation RCC in 26-year-old pregnant female. Her routine antenatal ultrasonography accidentally found a complex cystic right renal mass. Further radiologic studies revealed unilocular cyst with multiple mural nodules at inferior pole of right kidney, which was suspicious for RCC. She underwent right radical nephrectomy at 15 weeks gestation. Macroscopically, the cystic tumor was well encapsulated with multiple friable mural nodules on its inner surface. Microscopically, the tumor consisted of clear and eosinophilic/oncocytic voluminous cells arranged in papillary, trabecular, and nested/alveolar patterns. Occasional hyaline nodules and numerous psammoma bodies were present.

Immunohistochemically, the tumor showed strong nuclear positivity for TFE3. Epithelial membrane antigen, CD10, and E-cadherin were strongly positive. Cytokeratin AE1/AE3, cytokeratin CAM-5.2, calveolin, and parvalbumin were moderately positive. Cytokeratin 7, renal cell carcinoma antigen, and colloidal iron were focally weakly positive. BerEP4 and carbonic anhydrase IX were negative. Cytogenetically, the tumor harbored a novel variant translocation involving chromosomes X and 19, t(X;19)(p11.2;q13.1). Interphase FISH analysis performed on cultured and uncultured tumor cells using a dual-color break-apart DNA probe within the BCL3 gene on 19q13.3 was negative for the BCL3 gene rearrangement. She received no adjuvant therapy, delivered a normal term baby five months later, and is alive without evidence of disease 27 months after diagnosis and surgery. Unlike most recently reported Xp11.2 translocation RCCs in adult patients with aggressive clinical course, this adult case occurring during pregnancy with a novel translocation involving chromosome 19 followed an indolent clinical course.

Renal translocation carcinomas: clinicopathologic, immunohistochemical, and gene expression profiling analysis of 31 cases with a review of the literature

We report clinicopathologic features of a large series of renal translocation carcinomas from a multicentric study. Diagnosis was performed by cytogenetic examination of fresh material and/or by immunochemistry with antibodies directed against the C-terminal part of transcription factor E3 (TFE3) and native transcription factor EB (TFEB) proteins. Clinical data, follow-up, and histologic features were assessed. Antibodies against CK7, CD10, vimentin, epithelial membrane antigen, AE1-AE3, E-cadherin, alpha-methylacyl-coenzyme A racemase, melan A, and HMB45 were tested on tissue microarrays. Whole-genome microarray expression profiling was performed on 4 tumors. Twenty-nine cases were diagnosed as TFE3 and 2 as TFEB renal translocation carcinomas, including 13 males and 18 females, mean age 24.6 years. Two patients had a previous history of chemotherapy and 1 had a history of renal failure. Mean size of the tumor was 6.9 cm. Thirteen cases were > or = pT3 stage. Twelve cases were N+ or M+. Mean follow-up was 29.5 months. Three patients presented metastases and 5 have died. Mixed papillary and nested patterns with clear and/or eosinophilic cells represented the most consistent histologic appearance, with common foci of calcifications regardless of the type of translocation. Using a 30 mn incubation at room temperature, TFE3 immunostainings were positive in only 82% of our TFE3 translocation carcinomas. Both TFE3 and TFEB renal translocation carcinomas expressed CD10 and alpha-methylacyl-coenzyme A racemase in all cases. An expression of E-cadherin was observed in two-third of cases. Cytokeratins were expressed in less than one-third of cases. Melanocytic markers were expressed at least weakly in all cases except two. Unsupervised clustering on the basis of the gene expression profiling indicated a distinct subgroup of tumors. TRIM 63 glutathione S-transferase A1 and alanyl aminopeptidase are the main differentially expressed genes for this group of tumors. Our results suggest that these differentially expressed genes may serve as novel diagnostic or prognostic markers.

Translocation renal cell carcinoma: lack of negative impact due to lymph node spread

BACKGROUND

Pediatric renal cell carcinoma (RCC) is clinically distinct from adult RCC. Characterization of the unique biological and clinical features of pediatric RCC are required.

METHODS

A retrospective review and biological analysis of all RCC cases presenting to Cincinnati Children's Hospital Medical Center (CCHMC) in the last 30 years was undertaken. Cases were classified according to the recent World Heath Organization morphologic classification and according to TFE3/TFEB status. A literature review of pediatric TFE+ cases was performed.

RESULTS

Eleven cases of RCC with clinical data were identified in our institutional review as follows: 6 clear cell, 2 papillary, 2 translocation, and 1 sarcomatoid. Upon reanalysis, 1 papillary and 1 sarcomatoid were confirmed, 1 case was "unclassified", and 8 of 11 (72.7%) had features consistent with translocation morphology. Of these 8, all demonstrated immunoreactivity for TFE3 (7 patients) or TFEB (1 patient) protein. In 3 cases, cytogenetics was available, each demonstrating confirmatory MiTF/TFE translocations. Seven of 8 TFE+ RCC patients presented with TNM Stage III/IV disease. Literature analysis confirmed a significant increase in advanced stage presentation in pediatric TFE+ RCC compared with TFE- RCC. Fourteen of fifteen (93.3%) patients with TFE+ stage III/IV RCC due to lymph node spread (N+ M(0)) remain disease free with a median and mean follow-up of 4.4 and 6.3 years, respectively (range, 0.3-15.5).

CONCLUSIONS

Translocation morphology RCC is the predominant form of pediatric RCC, associated with an advanced stage at presentation. Patients with TFE+ N+ M(0) RCC maintain a favorable short-term prognosis after surgery alone. Young RCC patients should be screened for translocation morphology, and the screening information should be considered when debating adjuvant therapy.

Molecular mechanisms underlying the MiT translocation subgroup of renal cell carcinomas

Renal cell carcinomas (RCCs) represent a heterogeneous group of neoplasms, which differ in histological, pathologic and clinical characteristics. The tumors originate from different locations within the nephron and are accompanied by different recurrent (cyto)genetic anomalies. Recently, a novel subgroup of RCCs has been defined, i.e., the MiT translocation subgroup of RCCs. These tumors originate from the proximal tubule of the nephron, exhibit pleomorphic histological features including clear cell morphologies and papillary structures, and are found predominantly in children and young adults. In addition, these tumors are characterized by the occurrence of recurrent chromosomal translocations, which result in disruption and fusion of either the TFE3 or TFEB genes, both members of the MiT family of basic helix-loop-helix/leucine-zipper transcription factor genes. Hence the name MiT translocation subgroup of RCCs. In this review several features of this RCC subgroup will be discussed, including the molecular mechanisms that may underlie their development.

Xp11 translocation renal cell carcinoma in adults: expanded clinical, pathologic, and genetic spectrum

The recently recognized Xp11 translocation renal cell carcinomas (RCCs), all of which bear gene fusions involving the TFE3 transcription factor gene, comprise at least one-third of pediatric RCC. Only rare adult cases have been reported, without detailed pathologic analysis. We identified and analyzed 28 Xp11 translocation RCC in patients over the age of 20 years. All cases were confirmed by TFE3 immunohistochemistry, a sensitive and specific marker of neoplasms with TFE3 gene fusions, which can be applied to archival material. Three cases were also confirmed genetically. Patients ranged from ages 22 to 78 years, with a strong female predominance (F:M=22:6). These cancers tended to present at advanced stage; 14 of 28 presented at stage 4, whereas lymph nodes were involved by metastatic carcinoma in 11 of 13 cases in which they were resected. Previously not described and distinctive clinical presentations included dense tumor calcifications such that the tumor mimicked renal lithiasis, and obstruction of the renal pelvis promoting extensive obscuring xanthogranulomatous pyelonephritis. Previously unreported morphologic variants included tumor giant cells, fascicles of spindle cells, and a biphasic appearance that simulated the RCC characterized by a t(6;11)(p21;q12) chromosome translocation. One case harbored a novel variant translocation, t(X;3)(p11;q23). Five of 6 patients with 1 or more years of follow-up developed hematogenous metastases, with 2 dying within 1 year of diagnosis. Xp11 translocation RCC can occur in adults, and may be aggressive cancers that require morphologic distinction from clear cell and papillary RCC. Although they may be uncommon on a percentage basis, given the vast predominance of RCC in adults compared with children, adult Xp11 translocation RCC may well outnumber their pediatric counterparts.

Xp11 translocation renal cell carcinoma: delayed but massive and lethal metastases of a chemotherapy-associated secondary malignancy

A recently described subtype of renal cell carcinoma (RCC) bearing chromosome translocations involving a breakpoint at Xp11 and resulting in gene fusions involving the TFE3 transcription factor gene often presents in the pediatric population. Herein we describe an Xp11 translocation RCC associated with prior exposure to cytotoxic chemotherapy, which massively recurred and led to the patient's death 17 years later. This case highlights the association of these RCCs with prior chemotherapy exposure, the tendency of these RCCs to recur late, their unusual pattern of metastases, and the utility of TFE3 immunohistochemistry in confirming their diagnosis in archival pathologic specimens.

Pediatric renal cell carcinoma: clinical, pathologic, and molecular abnormalities associated with the members of the mit transcription factor family

We describe the clinical features, outcome, pathology, cytogenetics, and molecular aspects of 13 pediatric papillary renal cell carcinomas during a 19-year period. Seven cases (54%) had translocations involving Xp11.2 (TFE3). They were identified by cytogenetic, molecular, and/or immunohistochemical analyses. All Xp11.2+ translocations were TFE3+ by immunostaining. Cytogenetic and/or polymerase chain reaction analyses identified 3 cases with t(X17) and 1 case with t(1;17), and all had additional translocations. Histologic features in common in TFE3+ tumors also were present in some TFE3- tumors. One TFE3- tumor had complex cytogenetic abnormalities, 55XY,+2,del(3)(p14),+7,+8,+12,+13,+16,+17,+20[11 ], and 2 cases had normal karyotypes. None had t(6;11)/TFEB+ immunostaining. Five cases had focal, weak MITF tumor immunostaining. The key clinical findings were as follows: (1) The presence of an Xp11.2 (TFE3) translocation frequently is associated with advanced stage at initial examination. (2) All patients who underwent complete, partial nephrectomy with clear margins (adequate only for stage 1) and resection of metastases were alive and relapse-free at last follow-up. (3) The mean +/- SD event-free survival and overall survival rates at 5 years were both 92% +/- 7.4%. (4) One patients with a TFE3+ and MITF+ tumor and 66-87,XXY,der(1)t(1;8)del(4)(q?) der(11)t(11;15)der17t(X;17 abnormalities died 9 months after diagnosis.

Pediatric renal tumors: practical updates for the pathologist

Pediatric renal tumors were targeted by the National Wilms Tumor Study Group for 4 decades with extraordinary success. Within this historic context, this review provides a summary of the new Children's Oncology Group renal tumor protocols that will be opening in the very near future, focusing on their pathologic requirements. All renal tumors must first be registered on the Renal Tumor Classification and Banking Protocol, followed by registration on 1 of 4 primary therapeutic protocols based on histology, stage, and molecular analysis. This requires prompt submission of samples for molecular analysis and central pathologic review. Changes in staging criteria include classification of all tumor spillage as stage III, and requirement of regional lymph node evaluation for eligibility for stage I Wilms tumors (WTs) weighing less than 550 g in infants younger than 24 months and for stage I clear cell sarcoma. Patients with unilateral favorable histology WT with loss of heterozygosity for chromosomes 1p and 16q will receive more aggressive chemotherapy at each stage. Patients with bilateral WT and patients with diffuse hyperplastic perilobar nephroblastomatosis will be eligible for a novel therapeutic protocol requiring pathologic classification based on response of tumor to previous therapy. Stage I anaplastic WT will be targeted with more aggressive chemotherapy than in the past. For the first time, pediatric renal cell carcinoma will be eligible for a cooperative group protocol. All rhabdoid tumors outside the central nervous system will be eligible for a single protocol. In conclusion, these new protocols bring considerable change in their overall organization, in eligibility, and in therapy.

Five new cases of juvenile renal cell carcinoma with translocations involving Xp11.2: a cytogenetic and morphologic study

Two cases of renal cell carcinoma (RCC) carrying a t(X;1)(p11.2;q21) in a 12-year-old boy and a 14 year-old girl, two cases with a t(X;1)(p11.2;p34) in a 9-year-old boy and a 31-year-old woman, and one case with a t(X;17)(p11.2;q25) in a 15-year-old boy are reported. Two are likely papillary RCC, with clear or slightly eosinophilic cells, and two to a clear cell RCC; one shows a mixture of papillary and clear cell RCC architecture. Renal cell carcinomas with translocations involving Xp11.2 form a specific entity characterized by subtle pathologic features and younger age of occurrence, especially for those with the t(X;17).

PRCC-TFE3 renal carcinomas: morphologic, immunohistochemical, ultrastructural, and molecular analysis of an entity associated with the t(X;1)(p11.2;q21)

The reappraisal of genetically defined subsets of renal tumors can help to highlight the key pathologic features of specific neoplastic entities. We report the morphologic, immunophenotypic, ultrastructural, and molecular features of 11 renal carcinomas bearing a t(X;1)(p11.2;q21) and/or the resulting PRCC-TFE3 gene fusion. The male/female ratio was 4:7. Ten patients were in the age range of 9-29 years and one was 64 years old (mean 21.3 years, median 15 years). The predominant histologic pattern was nested, with islands of tumor cells compartmentalized by thin-walled capillary vasculature. Minor variations on this pattern yielded solid, acinar, alveolar, and tubular architecture. Papillary architecture was seen in nine cases, usually as a minor component. Neoplastic cells were typically characterized by irregularly shaped nuclei with vesicular chromatin and small nucleoli not visible with a 10x objective, and cytoplasm that ranged from clear to densely granular and eosinophilic. Mitoses were extremely rare; 5 were found in 900 high power fields examined from the 11 neoplasms. The most distinctive immunohistochemical feature of these neoplasms was moderate to intense nuclear labeling for TFE3 protein. These tumors were also consistently immunoreactive for the RCC antigen (10 of 11) and CD10 (9 of 9), whereas cytokeratin and epithelial membrane antigen were negative in four cases and were positive focally in the others. Ultrastructurally, all of the six neoplasms examined showed features consistent with conventional-type (clear cell) renal carcinoma, although two demonstrated distinctive intracisternal microtubules. Both tumors tested contained PRCC-TFE3 fusion transcripts. The differential diagnosis includes conventional-type papillary renal cell carcinoma, conventional-type (clear cell) renal carcinoma, and the ASPL-TFE3 renal carcinomas associated with the t(X;17)(p11.2;q25), with the latter two being morphologically the most similar to the t(X;1) renal carcinomas. Aside from their distinctive clinicopathologic features described here, there is experimental evidence suggesting that these tumors may show differential sensitivity to certain chemotherapeutic agents.

Molecular cytogenetics of t(X;1)(p11.2;q21) with complex rearrangements in a renal cell carcinoma

We report a new case of renal cell carcinoma with the translocation (X;1)(p11;q21) and complex structural rearrangements in a female patient of 64 years of age. We analyzed abnormalities using FISH to identify chromosomal rearrangements, and wonder whether the translocation (X;1) could represent a particular subentity in renal cell carcinoma with distinct histologic features.

Translocation (X;1) associated with a nonpapillary carcinoma in a young woman: a new definition for an Xp11.2 RCC subtype

We report a translocation (X;1)(p11.2;q21) associated with a nontubulopapillary renal cell carcinoma in a 23-year-old woman. To our knowledge this the first report of such an association. A review of the previously published cases of renal cell carcinoma with t(X;1) and its cytogenetic variants with Xp11.2 anomalies is included. The role of this karyotype abnormality as a clinical marker is discussed. The Xp11.2 abnormality could be a primary abnormality characterizing a particular type of RCC appearing in children and young adults of both sexes and in which the histological aspect is not specific.

Two new cases of papillary renal cell carcinoma with t(X;1)(p11;q21) in females

Two cases of papillary renal cell carcinoma (RCC) with a karyotype 46,X,t(X;1)(p11.2;q21) in two female patients aged 9 and 29 years are reported. These observations, and the review of the 17 reported cases with a translocation at band Xp11 confirm that this abnormality delineates a clinicopathological entity within the classical papillary RCC, characterized by the early age of occurrence and, probably, distinct histological features. Including these two new female cases, the sex ratio in cases with t(X;1) appears similar to that observed in the other papillary RCC.

Renal cell carcinoma: a rare source of cauda equina metastasis. Case report

The authors present the case of a patient in whom intradural metastasis from renal cell carcinoma spread to the cauda equina. To the authors' knowledge, this is only the second report of its kind. This male patient had undergone nephrectomy for the treatment of renal cell carcinoma for 5 years and was diagnosed as having metastatic lung disease 1 year prior to admission. The patient presented with lower back pain that radiated to both legs, but he exhibited no sensorimotor deficits. The majority of cauda equina tumors are primary tumors, and metastases are very rare. The literature is reviewed with reference to current molecular genetic paradigms of metastatic renal cell carcinoma.