Reappraisal of the papillary urothelial neoplasm of low malignant potential (PUNLMP).

Although the papillary urothelial neoplasm of low malignant potential (PUNLMP) diagnostic category was retained in the updated 2016 World Health Organisation (WHO) classification of tumours of the urinary system, there still exists a great deal of controversy regarding the biological behaviour of these tumours. We review PUNLMP tumours and histological grading with an emphasis on the histomorphological, genetic and clinical similarities between PUNLMP and low-grade non-invasive papillary urothelial carcinoma. A literature search using PubMed was performed. All relevant literature concerning PUNLMP and the grading of urothelial tumours was reviewed. PUNLMPs cannot be reliably distinguished from low-grade non-invasive papillary urothelial carcinomas based on the histomorphological criteria outlined in the WHO 2004/2016 classification system. PUNLMPs and low-grade non-invasive papillary urothelial carcinomas are not only morphologically similar, but also share similar molecular genetic alterations and a similar risk of recurrence and progression. In addition, there are no consensus recommendations for a different method of treatment and follow-up for these two tumour types. Attempting to distinguish PUNLMP from low-grade papillary urothelial carcinoma adds an unnecessary level of complexity to the grading and classification of urothelial tumours. We feel that PUNLMP terminology should be abandoned and that all such tumours should be classified as low-grade carcinomas until more objective determinants of clinical outcome can be established.

First dynamic model of dissolved organic carbon derived directly from high-frequency observations through contiguous storms.

The first dynamic model of dissolved organic carbon (DOC) export in streams derived directly from high frequency (subhourly) observations sampled at a regular interval through contiguous storms is presented. The optimal model, identified using the recently developed RIVC algorithm, captured the rapid dynamics of DOC load from 15 min monitored rainfall with high simulation efficiencies and constrained uncertainty with a second-order (two-pathway) structure. Most of the DOC export in the four headwater basins studied was associated with the faster hydrometric pathway (also modeled in parallel), and was soon exhausted in the slower pathway. A delay in the DOC mobilization became apparent as the ambient temperatures increased. These features of the component pathways were quantified in the dynamic response characteristics (DRCs) identified by RIVC. The model and associated DRCs are intended as a foundation for a better understanding of storm-related DOC dynamics and predictability, given the increasing availability of subhourly DOC concentration data.

KRAS mutation is present in a small subset of primary urinary bladder adenocarcinomas.

AIMS: To determine whether KRAS mutations occur in primary bladder adenocarcinoma. METHODS AND RESULTS: Twenty-six cases of primary urinary bladder adenocarcinoma were analysed. DNA was extracted from formalin-fixed, paraffin-embedded tissue and amplified with shifted termination assay technology, which recognizes wild-type or mutant target sequences and selectively extends detection primers with labelled nucleotides. A mutation in KRAS was found in three (11.5%) of 26 primary bladder adenocarcinomas. Two of these three cases exhibited a G13D mutation, whereas the remaining case contained a mutation in G12V. None of the ten cases of urothelial carcinoma with glandular differentiation displayed KRAS mutation. Colonic adenocarcinoma contained a KRAS mutation in 18 (33%) of 55 cases. There was no distinct difference with regard to grade, stage or outcome according to the limited clinicopathological data available. However, the two youngest patients, aged 32 and 39 years, in our study group, with a mean population age of 61 years, were found to have mutations in KRAS. CONCLUSIONS: KRAS mutations are present in a small subset of primary urinary bladder adenocarcinomas. Future clinical trials for treatment of bladder adenocarcinoma, employing targeted therapies similar to those used for treatment of colon cancer, may also benefit from the predictive implications of KRAS mutational testing.

Noninvasive papillary urothelial neoplasia (NIPUN): Renaming cancer.

Papillary urothelial neoplasm of low malignant potential (PUNLMP) terminology remains controversial given its reported recurrence rate, its low interobserver diagnostic reproducibility, and its morphologic and molecular genetic overlap with low-grade noninvasive papillary urothelial carcinoma. By contrast, referring to any noninvasive tumor as a "carcinoma" is also controversial. PUNLMP and low-grade noninvasive papillary urothelial carcinomas cannot be reliably distinguished from one another even by experienced pathologists. As both tumors are treated in an identical manner and have similar rates of recurrence and progression, attempting to make this distinction is unnecessary and of little clinical value. These tumor types should therefore be combined into a single category for grading purposes. We propose that all tumors currently classified as either PUNLMP or low-grade noninvasive papillary urothelial carcinoma be termed low-grade noninvasive papillary urothelial neoplasms (NIPUN). This could improve interobserver reproducibility without sacrificing the prognostic utility of histologic grading. PUNLMP terminology should be discontinued and the term "carcinoma" should be reserved only for tumors showing histologic evidence of invasion.

Discovery of substituted benzyl tetrazoles as histamine H3 receptor antagonists.

A series of potent and subtype selective H3 receptor antagonists containing a novel tetrazole core and diamine motif is reported. A one-pot multi-component Ugi reaction was utilised to rapidly develop the structure-activity relationships (SAR) of these compounds. Optimisation for liver microsome stability (t(1/2)>60 min), minimal CYP inhibition (IC(50)>50 microM) and high cell permeability (Caco-2 P(app) >20x10(-6) cm/s) identified several compounds with drug-like properties.

New approaches to prediction of immune responses to therapeutic proteins during preclinical development.

Clinical studies show that immunogenicity observed against therapeutic proteins can limit efficacy and reduce the safety of the treatment. It is therefore beneficial to be able to predict the immunogenicity of therapeutic proteins before they enter the clinic. Studies using deimmunized proteins have highlighted the importance of T-cell epitopes in the generation of undesirable immunogenicity. In silico, in vitro, ex vivo and in vivo methods have therefore been developed that focus on identification of CD4+ T-cell epitopes in the sequence of therapeutic proteins. A case study of existing therapeutic proteins is presented to review these different approaches in order to assess their utility in predicting immunogenic potential.

Molecular evidence for independent origin of multifocal neuroendocrine tumors of the enteropancreatic axis.

Neuroendocrine tumors of the enteropancreatic axis are often multifocal. We have investigated whether multifocal intestinal carcinoid tumors and multifocal pancreatic endocrine tumors arise independently or whether they originate from a single clone with subsequent intramural or intrapancreatic spread. Twenty-four cases, including 16 multifocal intestinal carcinoid tumors and eight multifocal pancreatic endocrine tumors, were studied. Genomic DNA samples were prepared from 72 distinct tumor nodules using laser capture microdissection. Loss of heterozygosity (LOH) assays were done using markers for putative tumor suppressor genes located on chromosomes 9p21 (p16), 11q13 (MEN1), 11q23 (SDHD), 16q21, 18q21, and 18q22-23. In addition, X chromosome inactivation analysis was done on the tumors from eight female patients. Twenty-two of 24 (92%) cases showed allelic loss in at least one tumor focus, including 15 of 16 (94%) cases of multifocal carcinoid tumors and 7 of 8 (88%) cases of multifocal pancreatic endocrine tumors. Eleven of 24 (46%) cases exhibited a different LOH pattern for each tumor. Additionally, 9 of 24 (38%) cases showed different LOH patterns among some of the coexisting tumors, whereas other coexisting tumors displayed the same allelic loss pattern. Two of 24 (8%) cases showed the same LOH pattern in every individual tumor. X chromosome inactivation analysis showed a discordant pattern of nonrandom X chromosome inactivation in two of six informative cases and concordant pattern of nonrandom X chromosome inactivation in the four remaining informative cases. Our data suggest that some multifocal neuroendocrine tumors of the enteropancreatic axis arise independently, whereas others originate as a single clone with subsequent local and discontinuous metastasis.

Identification and removal of immunogenicity in therapeutic proteins.

The development of anti-therapeutic protein immune responses in patients can be a severe complication of treatment with this class of pharmaceuticals. Antibodies generated against therapeutic proteins limit the clinical efficacy of these agents by neutralizing their biological activity and/or enhancing their clearance. An assessment of the propensity of protein therapeutics to elicit immune responses in patients is likely to become an essential part of their preclinical development. It is clear that CD4+ T-cells are an important factor in the development of long-lived, class-switched, high-affinity antitherapeutic protein antibodies. The increased risk of immunogenicity that is attributed to the presence of T-cell epitopes in therapeutic protein sequences has led to the development of a variety of methods for locating T-cell epitopes and identifying binding peptide amino acids that are important for interacting with either major histocompatibility complex class II molecules or the T-cell receptors. Manipulation of these key residues to disrupt these interactions while maintaining biological activity can result in modified therapeutic proteins with reduced immunogenicity.

Genetically heterogeneous and clonally unrelated metastases may arise in patients with cutaneous melanoma.

Melanoma of the skin frequently metastasizes to multiple regional lymph nodes and to distant sites. It is uncertain whether all metastases originate from the same tumor clone or whether the genetic heterogeneity of the primary tumor is reflected in the multiple metastases. A total of 73 archival, formalin-fixed, paraffin-embedded, melanoma lesions, including 13 primary tumors and 60 metastases, were studied from 13 patients each having 2 or more metastatic tumors. Genomic DNA samples were prepared from tissue sections using laser-assisted microdissection. We find that the majority of melanoma metastases share a common clonal origin with the matched primary tumor. However, significant genetic divergence occurs frequently during the clonal evolution of metastatic melanoma. In addition, using X-chromosome inactivation analysis, we find that, in some cases, multiple coexisting metastases seem to be derived from different, genetically unrelated tumor clones, implying that some primary tumors may arise from more than a single transformed melanocyte.

Urothelial carcinoma with an inverted growth pattern can be distinguished from inverted papilloma by fluorescence in situ hybridization, immunohistochemistry, and morphologic analysis.

Inverted papilloma of the urinary bladder and urothelial carcinoma with an inverted (endophytic) growth pattern may be difficult to distinguish histologically, especially in small biopsies. The distinction is important as these lesions have very different biologic behaviors and are treated differently. We examined histologic features and undertook immunohistochemical staining and UroVysion fluorescence in situ hybridization (FISH) to determine whether these methods could aid in making this distinction. We examined histologic sections from 15 inverted papillomas and 29 urothelial carcinomas with an inverted growth pattern. Each tumor was stained with antibodies to Ki-67, p53, and cytokeratin 20. In addition, each tumor was examined with UroVysion FISH for gains of chromosomes 3, 7, and 17 and for loss of chromosome 9p21 signals. None of the inverted papillomas stained positively for Ki-67 or for cytokeratin 20. Only 1 of 15 inverted papillomas stained positively for p53. By contrast, 66%, 59%, and 59% of urothelial carcinomas with an inverted growth pattern stained positively for Ki-67, p53, and cytokeratin 20, respectively. Only 3 of the urothelial carcinomas stained negatively for all 3 immunohistochemical markers. UroVysion FISH produced normal results for all cases of inverted papilloma. By contrast, 21 of 29 cases (72%) of urothelial carcinoma with an inverted growth pattern demonstrated chromosomal abnormalities typical of urothelial cancer and were considered positive by UroVysion FISH criteria. Morphologic features, as well as immunohistochemical stains (including stains for Ki-67, p53, and cytokeratin 20) and/or UroVysion FISH can help to distinguish inverted papilloma from urothelial carcinoma with an inverted growth pattern.

Molecular evidence for the same clonal origin of multifocal papillary thyroid carcinomas.

PURPOSE: Patients with papillary thyroid carcinoma often have two or more distinct papillary tumors at thyroidectomy. Whether these multifocal papillary lesions are clonally related or whether they arise independently is unknown as previous studies have shown conflicting results. Molecular analysis of microsatellite alterations and X-chromosome inactivation status in separate tumors from the same patient can be used to define the genetic relationships among the multiple coexisting tumors. EXPERIMENTAL DESIGN: We examined 64 separate tumors from 22 female patients who underwent thyroidectomy for thyroid carcinoma. All patients had multiple and separate papillary carcinomas (range, two to six). Genomic DNA samples were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-capture microdissection. Loss of heterozygosity assays for three microsatellite polymorphic markers for putative tumor suppressor genes on chromosomes 3p25 (D3S1597), 9p21 (D9S161), and 18p11.22-p11 (D18S53) were done. In addition, X-chromosome inactivation analysis was done on the tumors from all patients. RESULTS: Twenty of 22 (91%) cases showed allelic loss in one or more of the papillary lesions in at least one of the three polymorphic markers analyzed. Concordant allelic loss patterns between coexisting papillary tumors were seen in 20 of 23 (87%) cases. A concordant pattern of nonrandom X-chromosome inactivation in the multiple coexisting papillary lesions was seen in all informative cases. CONCLUSION: Our data suggest that the multifocal tumors in patients with papillary thyroid carcinoma often arise from the same clone. Thus, intrathryoid metastasis may play an important role in the spread of papillary thyroid carcinoma, a finding that has important therapeutic, diagnostic, and prognostic implications.

Clonal origin of metastatic testicular teratomas.

PURPOSE: Testicular teratomas in adult patients are histologically diverse tumors that frequently coexist with other germ cell tumor (GCT) components. These mixed GCTs often metastasize to retroperitoneal lymph nodes where multiple GCT elements are frequently present in the same metastatic lesion. Neither the genetic relationships among the different components in metastatic lesions nor the relationships between primary and metastatic GCT components have been elucidated. EXPERIMENTAL DESIGN: We examined metastases from 31 patients who underwent primary retroperitoneal lymph node dissection for metastatic testicular GCT. All patients had metastatic mature teratoma with one or more other GCT components. This study included a total of 72 metastatic GCT components and 16 primary GCT components from 31 patients. Genomic DNA samples from each component were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-assisted microdissection. Loss of heterozygosity (LOH) assays for seven microsatellite polymorphic markers on chromosomes 1p36 (D1S1646), 9p21 (D9S171 and IFNA), 9q21 (D9S303), 13q22-q31 (D13S317), 18q22 (D18S543), and 18q21 (D18S60) were done to assess clonality. RESULTS: Twenty-nine of 31 (94%) cases showed allelic loss in one or more components of the metastatic GCTs. Twenty-nine of 31 mature teratomas showed allelic loss in at least one of seven microsatellite polymorphic markers analyzed. The frequency of allelic loss in informative cases of metastatic mature teratoma was 27% (8 of 30) with D1S1646, 34% (10 of 29) with D9S171, 37% (10 of 27) with IFNA, 27% (8 of 30) with D9S303, 46% (13 of 28) with D13S317, 26% (7 of 27) with D18S543, and 36% (10 of 28) with D18S60. Completely concordant allelic loss patterns between the mature teratoma and all of the other metastatic GCT components were seen in 26 of 29 cases in which the mature teratoma component showed LOH. Nearly identical allelic loss patterns were seen in the three remaining cases. In six cases analyzed, LOH patterns of each metastatic component were compared with each GCT component of the primary testicular tumor. In all six cases, each primary and metastatic component showed an identical pattern of allelic loss. CONCLUSION: Our data support the common clonal origin of metastatic mature teratomas with other components of metastatic testicular GCTs and with each component of the primary tumor.

Sampling frequency for water quality variables in streams: Systems analysis to quantify minimum monitoring rates.

Insufficient temporal monitoring of water quality in streams or engineered drains alters the apparent shape of storm chemographs, resulting in shifted model parameterisations and changed interpretations of solute sources that have produced episodes of poor water quality. This so-called 'aliasing' phenomenon is poorly recognised in water research. Using advances in in-situ sensor technology it is now possible to monitor sufficiently frequently to avoid the onset of aliasing. A systems modelling procedure is presented allowing objective identification of sampling rates needed to avoid aliasing within strongly rainfall-driven chemical dynamics. In this study aliasing of storm chemograph shapes was quantified by changes in the time constant parameter (TC) of transfer functions. As a proportion of the original TC, the onset of aliasing varied between watersheds, ranging from 3.9-7.7 to 54-79 %TC (or 110-160 to 300-600 min). However, a minimum monitoring rate could be identified for all datasets if the modelling results were presented in the form of a new statistic, ΔTC. For the eight H+, DOC and NO3-N datasets examined from a range of watershed settings, an empirically-derived threshold of 1.3(ΔTC) could be used to quantify minimum monitoring rates within sampling protocols to avoid artefacts in subsequent data analysis.

Screening for intratubular germ cell neoplasia of the testis using OCT4 immunohistochemistry.

Specific populations of patients are at high risk for the development of germ cell neoplasia. OCT4 has been shown to be a sensitive and specific marker for intratubular germ cell neoplasia of the testis. Whether or not OCT4 immunohistochemistry is a clinically useful screening tool in patients at risk for developing malignant germ cell tumors is not currently known. We undertook immunohistochemical staining for OCT4 in a large series of patients who underwent testicular biopsy or orchiectomy for reasons other than for management of a testicular mass suspicious for malignancy (infertility, cryptorchidism, atrophic testicle, etc.). OCT4 nuclear staining was identified in germ cells in 6 of 157 patients, all of whom had clinical risk factors for the development of testicular germ cell tumors. Two of the 6 patients were under 1.5 years of age, making the significance of OCT4 positivity less certain in these cases. The remaining patients with OCT4-positive germ cells consisted of 3 adults and 1 7-year-old child. Intratubular germ cell neoplasia was identified by light microscopy in only 1 of the 6 OCT4-positive cases. OCT4 immunostaining was negative in all patients who presented with infertility and who had no additional germ cell tumor risk factors. OCT4 immunohistochemistry may be useful in identifying early forms of preinvasive germ cell neoplasia in patients with risk factors for the development of malignant testicular germ cell tumors. The low incidence of OCT4 positivity in the adult infertility patients argues against the routine use of OCT4 immunostains in testicular biopsies for infertility unless additional risk factors are present.

OCT4 is superior to CD30 in the diagnosis of metastatic embryonal carcinomas after chemotherapy.

Correctly diagnosing a metastatic germ cell tumor after chemotherapy may be challenging because of the diverse morphological manifestations of postchemotherapy tumors. Both OCT4 and CD30 are sensitive markers for the identification of primary embryonal carcinomas; however, loss of expression of CD30 (65%) has been reported in metastatic embryonal carcinomas after chemotherapy. The present study was conducted to evaluate the expression patterns of OCT4 and CD30 in postchemotherapy metastatic embryonal carcinomas and to compare their utility as diagnostic tools. Twenty-five cases of metastatic embryonal carcinoma after chemotherapy were immunohistochemically analyzed for CD30, OCT4, and cytokeratin AE1/AE3 expression. The staining intensities and the percentages of positively staining tumor cells were recorded. Nineteen (76%) of 25 cases revealed diffuse, moderate to strong nuclear OCT4 staining in postchemotherapy embryonal carcinomas. Among these 19 OCT4-positive cases, 8 also revealed diffuse and moderate to strong membranous CD30 staining. Seven of these OCT4-positive cases retained focal and weak CD30 expression. The remaining 4 OCT4-positive cases demonstrated a complete loss of CD30 expression. The 19 OCT4-positive cases showed a positive but variable cytokeratin AE1/AE3 expression pattern. Six (24%) of 25 cases were negative for both CD30 and OCT4 but demonstrated diffuse and strong cytokeratin AE1/AE3 staining. OCT4 is a useful diagnostic marker to identify metastatic embryonal carcinomas after chemotherapy, with a better sensitivity than CD30.

Cytokeratin and CD30 expression in dysgerminoma.

Dysgerminoma is a malignant germ cell tumor of the ovary that shares morphological, immunophenotypic, and genetic features with its testicular counterpart, seminoma. Recent evidence supports the hypothesis that seminoma can differentiate into non-seminomatous germ cell tumor types. The progression of these tumors can be measured by their acquisition of the potential to express cytokeratin intermediate filaments, a characteristic specific to epithelial differentiation. Although testicular seminomas have been widely investigated, little is known about cytokeratin or E-cadherin expression in dysgerminomas. We investigated 26 formalin-fixed, paraffin-embedded ovarian dysgerminomas with immunohistochemical stains for CAM5.2, AE1/AE3, epithelial membrane antigen, cytokeratin 7, cytokeratin 20, high-molecular-weight keratin, and E-cadherin. In addition, we investigated the CD30 and vimentin immunoreactivity of these tumors. Immunoreactivity for CAM5.2 and for AE1/AE3 was present in more than 10% of neoplastic cells in 5 (19.2%) of 26 cases and in 2 (7.7%) of 26 cases, respectively. Cytokeratin 7 showed only focal positivity and never showed positive staining in greater than 10% of dysgerminoma cells. E-cadherin staining was positive in 2 cases showing weak membranous immunostaining in more than 10% of cells. Vimentin immunoreactivity was observed in only 2 dysgerminomas, both of which had less than 10% of the neoplastic cells staining. Cytokeratin 20, epithelial membrane antigen, high-molecular-weight keratin, and CD30 were consistently negative in all cases. Our study demonstrates that cytokeratin expression in dysgerminomas is not unusual and is consistent with the hypothesis that dysgerminomas have the capacity to differentiate along epithelial lines. Furthermore, the immunohistochemical staining patterns for cytokeratins, E-cadherin, and CD30 in dysgerminomas need to be considered when assessing differential diagnoses in difficult cases of primary ovarian tumors.

Molecular evidence supporting field effect in urothelial carcinogenesis.

PURPOSE: Human urothelial carcinoma is thought to arise from a field change that affects the entire urothelium. Multifocality of urothelial carcinoma is a common finding at endoscopy and surgery. Whether these coexisting tumors arise independently or are derived from the same tumor clone is uncertain. Molecular analysis of microsatellite alterations and X-chromosome inactivation status in the cells from each coexisting tumor may further our understanding of urothelial carcinogenesis. EXPERIMENTAL DESIGN: We examined 58 tumors from 21 patients who underwent surgical excision for urothelial carcinoma. All patients had multiple separate foci of urothelial carcinoma (two to four) within the urinary tract. Genomic DNA samples were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-capture microdissection. Loss of heterozygosity (LOH) assays for three microsatellite polymorphic markers on chromosome 9p21 (IFNA and D9S171), regions of putative tumor suppressor gene p16, and on chromosome 17p13 (TP53), the p53 tumor suppressor gene locus, were done. X-chromosome inactivation analysis was done on the urothelial tumors from 11 female patients. RESULTS: Seventeen of 21 (81%) cases showed allelic loss in one or more of the urothelial tumors in at least one of the three polymorphic markers analyzed. Concordant allelic loss patterns between each coexisting urothelial tumor were seen in only 3 of 21 (14%) cases. A concordant pattern of nonrandom X-chromosome inactivation in the multiple coexisting urothelial tumors was seen in only 3 of 11 female patients; of these 3 cases, only one displayed an identical allelic loss pattern in all of the tumors on LOH analysis. CONCLUSION: LOH and X-chromosome inactivation assays show that the coexisting tumors in many cases of multifocal urothelial carcinoma have a unique clonal origin and arise from independently transformed progenitor urothelial cells, supporting the "field effect" theory for urothelial carcinogenesis.

Molecular genetic evidence for the independent origin of multifocal papillary tumors in patients with papillary renal cell carcinomas.

PURPOSE: In patients with papillary renal cell carcinoma, it is not uncommon to find two or more anatomically distinct and histologically similar tumors at radical nephrectomy. Whether these multiple papillary lesions result from intrarenal metastasis or arise independently is unknown. Previous studies have shown that multifocal clear cell renal cell carcinomas express identical allelic loss and shift patterns in the different tumors within the same kidney, consistent with a clonal origin. However, similar clonality assays for multifocal papillary renal cell neoplasia have not been done. Molecular analysis of microsatellite and chromosome alterations and X-chromosome inactivation status in separate tumors in the same patient can be used to study the genetic relationships among the coexisting multiple tumors. EXPERIMENTAL DESIGN: We examined specimens from 21 patients who underwent radical nephrectomy for renal cell carcinoma. All patients had multiple separate papillary lesions (ranging from 2 to 5). Eighteen patients had multiple papillary renal cell carcinomas. Seven had one or more papillary renal cell carcinomas with coexisting papillary adenomas. Genomic DNA samples were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-capture microdissection. Loss of heterozygosity assays were done for six microsatellite polymorphic markers for putative tumor suppressor genes on chromosomes 3p14 (D3S1285), 7q31 (D7S522), 9p21 (D9S171), 16q23 (D16S507), 17q21 (D17S1795), and 17p13 (TP53). X-chromosome inactivation analyses were done on the papillary kidney tumors from three female patients. Fluorescence in situ hybridization analysis was done on the tumors of selected patients showing allelic loss at loci on chromosome 7 and/or chromosome 17. RESULTS: Twenty of 21 (95%) cases showed allelic loss in one or more of the papillary lesions in at least one of the six polymorphic markers analyzed. A concordant allelic loss pattern between each coexisting kidney tumor was seen in only 1 of 21 (5%) cases. A concordant pattern of nonrandom X-chromosome inactivation in the coexisting multiple papillary lesions was seen in two of three female patients. A discordant pattern of X-chromosome inactivation was seen in the tumors of the other female patient. Fluorescence in situ hybridization showed that the majority of tumors analyzed had gains of chromosomes 7 and 17. Two patients had one tumor with chromosomal gain and another separate tumor that did not. CONCLUSION: Our data suggest that, unlike multifocal clear cell renal cell carcinomas, the multiple tumors in patients with papillary renal cell carcinoma arise independently. Thus, intrarenal metastasis does not seem to play an important role in the spread of papillary renal cell carcinoma, a finding that has surgical, therapeutic, and prognostic implications.