Ultrastructural identification of a proximal tubulopathy without crystals in a relapsed multiple myeloma patient.

A multiple myeloma patient, who had been treated with a hematopoietic stem cell transplant, underwent a renal biopsy for investigation of a possible relapse of disease as indicated by increased serum creatinine and positive urinary Bence-Jones protein containing increased kappa light chain. Paraprotein-related renal disease was not evident by light microscopy or immunofluorescence microscopy however electron microscopy demonstrated a proximal tubulopathy with intracytoplasmic non-crystalline inclusions. The ultrastructural findings suggested possible end-organ involvement by the disease and follow-up studies subsequently revealed a relapsed multiple myeloma in the patient. The case exemplifies the usefulness of electron microscopy in detecting paraproteins that, in some instances, may be difficult to demonstrate by other techniques.

Leukocyte telomere length and renal cell carcinoma survival in two studies.

BACKGROUND: Leukocyte telomere length (LTL) is a potential biomarker of cancer prognosis; however, evidence for renal cell carcinoma (RCC) is inconsistent. METHODS: We investigated LTL and RCC-specific survival among 684 cases from the US kidney cancer study (USKC) and 241 cases from the prostate, lung, colorectal, and ovarian cancer screening trial (PLCO). Leukocyte telomere length was measured by quantitative polymerase chain reaction, and hazard ratios (HRs) and 95% confidence intervals (CIs) computed using multivariable Cox models. RESULTS: Short LTL was associated with poorer disease-specific survival in both USKC (lowest vs highest quartile: HR: 2.3, 95% CI: 1.2-4.4; P for trend=0.02) and PLCO (HR: 2.4, 95% CI: 1.0-5.4; P=0.04). Among USKC cases, the association was strongest for stage-I RCC (HR: 5.5, 95% CI: 1.6-19.0; P=0.006). CONCLUSIONS: Our findings suggest that shorter LTL is an independent marker of poor RCC prognosis, particularly for stage-I disease.

Age-Related Renal Microvascular Changes: Evaluation by Three-Dimensional Digital Imaging of the Human Renal Microcirculation Using Virtual Microscopy.

The renal microvasculature is targeted during aging, sometimes producing chronic kidney disease (CKD). Overdiagnosis of CKD in older persons is concerning. To prevent it, a new concept of "healthy aging" is arising from a healthy renal donor study. We investigated the renal microcirculatory changes of three older persons and compared them with that of one patient with nephrosclerosis using a three-dimensional (3D) reconstruction technique that we previously developed. This method uses a virtual slide system and paraffin-embedded serial sections of surgical material that was double-immunostained by anti-CD34 and anti-α smooth muscle actin (SMA) antibodies for detecting endothelial cells and medial smooth muscle cells, respectively. In all cases, the 3D images proved that arteriosclerotic changes in large proximal interlobular arteries did not directly induce distal arterial change or glomerulosclerosis. The nephrosclerotic patient showed severe hyalinosis with luminal narrowing of small arteries directly inducing glomerulosclerosis. We also visualized an atubular glomerulus and intraglomerular dilatation of an afferent arteriole during healthy aging on the 3D image and showed that microcirculatory changes were responsible for them. Thus, we successfully visualized healthy aged kidneys on 3D images and confirmed the underlying pathology. This method has the ability to investigate renal microcirculatory damage during healthy aging.

Prominent apical cytoplasmic bleb formation in metanephric adenoma: report of a case.

In a case of metanephric adenoma of the kidney, many apical cytoplasmic blebs were found on the luminal surface of tumor cells. The tumor, measuring 15 mm in diameter, was found incidentally in the right kidney of a 40-year-old woman. It consisted of a dense proliferation of cuboidal cells forming small tubules of round or irregular shape. The apical portion of the cytoplasm of tumor cells exhibited club-shaped expansion or dome-like protrusion which was largely occupied by numerous free ribosomes. The neck portion of the protruded apical cytoplasm was constricted, and the apical cytoplasm appeared to have been "pinched-off" and shed into the lumen. The prominent formation of apical cytoplasmic blebs has, to our knowledge, not been documented in renal tumors except in angiomyoadenomatous tumors. Its pathological significance is unknown, but it most likely represents a response of tumor cells to some hypoxic or toxic cellular injuries.

Review of renal cell carcinoma with rhabdoid features with focus on clinical and pathobiological aspects.

Rhabdoid morphology in renal cell carcinoma (RCC) may, like sarcomatoid change, be perceived as a type of dedifferentiation, and is a poor prognostic factor. Histologically, rhabdoid neoplastic cells are round to polygonal cells with globular eosinophilic cytoplasmic inclusions and eccentric vesicular nuclei and enlarged nucleoli. All types of RCC, including clear cell, papillary, chromophobe, collecting duct carcinoma, renal medullary carcinoma, acquired cystic disease-associated RCC, ALK-positive renal cancer and unclassified RCC, may display a variably prominent rhabdoid phenotype. Immunohistochemically, the cytoplasm of rhabdoid cells shows positivity for vimentin and/or cytokeratin. Ultrastructurally, cytoplasmic whorls/aggregates of intermediate filaments correspond to light microscopically observed inclusions. Genetically, a previous report suggests that combined loss of BAP1 and PBRM1 may be associated with rhabdoid morphology. As with sarcomatoid change, pathologists should describe, estimate and state the proportion of tumor cells with a rhabdoid phenotype in the routine pathology report of RCC.

[Clinicopathologic features of clear cell papillary renal cell carcinoma].

OBJECTIVE: To study the clinicopathological features, differential diagnosis and prognosis of clear cell papillary renal cell carcinoma (CCPRCC). METHODS: The histological, immunohistochemical, and molecular features were studied in 11 cases and follow-up data were also analyzed. RESULTS: There were a total of 3 females and 8 males. The age of patients were ranged from 33 to 72 years(mean age 52.5 years). The diameters of tumors varied from 1cm to 4 cm. Histologically, papillary and cystic architecture were present at least focally in all tumors. The papillae were covered by small to medium-sized cuboidal cells with abundant clear cytoplasm and often showed extensive secondary branching, which were often folded and densely packed, resulting in a solid appearance. The nuclei were round and uniform in shape; nucleoli were not prominent (Fuhrman grade 1 or 2). Neither mitotic figures nor necrosis was present. All 11 cases exhibited moderate to strong positivity for CK7, CA9, vimentin, and HIF-1α, coupled with negative reactions for CD10, P504S, and TFE3. Ksp-cadherin was positively expressed in 8 cases.VHL gene mutations were not found in all 11 cases. Losses of chromosomes 3 (monoploid chromosome 3) was detected in 3 cases. CONCLUSIONS: CCPRCC is uncommon and seemed to be an indolent tumor. The differential diagnosis should be included tumors, which harbor clear cell and papillary structure including clear cell renal cell carcinoma, papillary renal cell carcinoma, Xp11 translocation renal cell carcinoma, and CCPRCC. Immunohistochemical and molecular analysis may be help for its diagnosis.

Evaluation of morphologically unclassified renal cell carcinoma with electron microscopy and novel renal markers: implications for tumor reclassification.

Despite progress in the classification of renal cell carcinomas (RCC), a subset of these carcinomas remains unclassified (RCC-U). Patients with RCC-U usually present at a late stage and have a poor prognosis. Several studies have attempted to extract new classifications of newly recognized renal carcinomas from the group of RCC-U. However, to date, no studies in the literature have attempted to characterize the RCC-U with unrecognizable cell types beyond the morphologic evaluation on H&E-stained sections. The purpose of this study was to evaluate this group of RCC-U using electron microscopy and novel renal markers. Ten cases of such RCC-U were identified for this study. At the ultrastructural level, they did not show typical morphology that resembled any of the well-studied, recognizable subtypes of RCC. However, they did reveal features of renal tubular epithelial differentiation. The histologic, ultrastructural, and immunophenotypic features indicated that these tumors are poorly differentiated renal epithelial tumors, possibly derived from the proximal nephron, with an immunohistochemical profile similar to high-grade clear cell RCC. It is, therefore, proposed that this group of renal carcinomas be renamed "poorly differentiated renal cell carcinoma, not otherwise specified." The current study showed that PAX-8 and carbonic anhydrase IX are reliable markers for this novel group of renal carcinoma, and that electron microscopy is an important adjunct in the evaluation of new and unusual renal entities.

Possible pathogenetic relationship between Fabry disease and renal cell carcinoma.

The occurrence of renal cell carcinoma (RCC) in Fabry disease (FD) is a rare event. We report a deep ultrastructural study of RCC in a patient with a previous histological diagnosis of FD. In order to highlight analogies and differences between the two histological samples, we used the nephrectomy specimen as a 'repeat biopsy', making a dynamic analysis of the evolution of the disease-related kidney damage. Secondly, a comparative ultrastructural analysis between non-neoplastic tissue and cancer demonstrated for the first time the presence of zebra bodies in the tumor cells. Finally, a hypothetical speculation about the relationship between the lysosomal accumulation, the oxidative damage and the genesis of the tumor was performed. The link connected the accumulation of glycosphingolipid globotriaosylceramide, characteristic of FD, with the expression of CD74 and macrophage migration inhibitory factor that may play an important role in tumorigenesis regulated by the Von Hippel-Lindau/hypoxia-inducible factor 1α pathway.

Overexpression of miR-210, a downstream target of HIF1α, causes centrosome amplification in renal carcinoma cells.

MiR-210 is significantly up-regulated in clear cell renal cell carcinoma (CCC), but the mechanism and biological consequences of miR-210 up-regulation are poorly understood. Here, we show that miR-210 is highly expressed in renal carcinoma cell lines and that its expression is clearly correlated with accumulation of hypoxia-inducible factor 1α (HIF1α) under normoxia as well as hypoxia, suggesting that miR-210 up-regulation in renal carcinoma cells is most likely due to accumulation of HIF1α. To reveal the effects of miR-210 up-regulation, the miR-210 precursor was transfected into renal carcinoma cells. After transfection, the cells accumulated at the G2/M phase of the cell cycle and their viability was decreased, suggesting that miR-210 overexpression may trigger an event that hinders normal cell division. Immunocytochemistry demonstrated a multipolar spindle accompanied by centrosome amplification in cells overexpressing miR-210. It has been reported that centrosome amplification induces chromosome mis-segregation, finally leading to chromosome instability and aneuploidy. Indeed, the proportion of aneuploid cells (>4n) was increased in miR-210 overexpressed cells. By using the TargetScan and PicTar algorithms, E2F3 was identified as one of the possible targets of miR-210 and was suppressed at the protein level by miR-210. Moreover, the proportion of aneuploid cells was increased in E2F3 siRNA transfected cells. On the basis of these results, we propose that miR-210 up-regulation due to HIF1α accumulation may induce aneuploidy via E2F3 down-regulation at least in part, and may play a role in tumourigenesis and/or progression of CCC.

Biphasic alveolosquamoid renal carcinoma: a histomorphological, immunohistochemical, molecular genetic, and ultrastructural study of a distinctive morphologic variant of renal cell carcinoma.

Only a few cases of sarcomatoid renal cell carcinomas (RCCs) with squamous differentiation have been published. We present 2 RCCs exhibiting a hitherto not reported biphasic neoplastic cell population exhibiting a predominantly alveolar architecture where squamoid differentiation was identified in one of the neoplastic cell populations. None of the tumors showed chromophobe features or any evidence of sarcomatoid transformation. The tumors arose in 2 adult patients and were characterized by routine histology, immunohistochemistry, ultrastructure, array comparative genomic hybridization, confirmatory fluorescent in situ hybridization, and loss of heterozygosity analysis. Tumors measured 3 and 4 cm and were located within the renal parenchyma and had no pelvicalyceal connection. Both tumors were composed of a distinctly dual-cell population. The larger tumor cells displayed squamoid features and formed round well-demarcated solid alveolated islands that, in large parts, were surrounded by a smaller neoplastic cell component. The squamoid cells were immunoreactive for cytokeratins (CKs) (AE1-AE3, Cam 5.2, CK5/6, CK7, and CK20), epithelial membrane antigen, racemase/AMACR, and carboanhydrase IX (in 1 case focally). The small cell population was positive for CK7, epithelial membrane antigen, and racemase/AMACR, whereas CK20, AE1-3, and carboanhydrase IX were negative. CD10 was focally positive in the large squamoid cells in 1 case. Cathepsin K, E-cadherin, and CD117 displayed focal positivity in 1 case. Vimentin, RCC marker, parvalbumin, S100 protein, S100 A1, p63, p53, CDX2, uroplakin III, HMB45, TFE3, WT1, synaptophysin, chromogranin A, thyroglobulin, and TTF1 were negative. The proliferative activity (Ki-67) was low (1%) in the small cell component in both cases, whereas the large neoplastic tumor cells displayed a significantly higher proliferation (20%-35%). Ultrastructurally, desmosomes and tonofilaments were identified in the large tumor cells, confirming squamoid differentiation in a subset of tumor cells. Array comparative genomic hybridization of 1 analyzable case (confirmed with fluorescent in situ hybridization and loss of heterozygosity analysis) revealed partial or complete losses of chromosomes 2, 5, 6, 9, 12, 15, 16, 17, 18 and 22, (including biallelic loss of CDKN2A locus) and partial gains of chromosomes 1, 5, 11, 12 and 13. Follow-up at 6 years showed no recurrence or metastasis in 1 patient. The other (male) patients had a subcutaneous metastasis at presentation, but during a 1-year follow-up no evidence of recurrence or further metastatic events have been documented. Our data indicate that biphasic alveolosquamoid renal carcinoma is a unique and distinctive tumor. The large squamoid and small tumor cells have overlapping but still distinctive immunohistochemical patterns of protein expression. Multiple chromosomal aberrations were identified, some of them located in regions with known tumor suppressor genes and oncogenes.

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.

Chromophobe renal cell carcinoma with prominent lymph node metastasis and polysomy of chromosome 21: poorly differentiated form or "presarcomatoid" form?

Lymph node metastasis of chromophobe renal cell carcinoma (RCC) is extremely rare. It has been recently reported that sarcomatoid chromophobe RCC frequently show polysomy of chromosomes 1, 2, 6, 10, and 17. In this article, we report an unusual case of chromophobe RCC. A 42-year-old Japanese woman presented with hematuria and complained of inguinal pain 2 months after the initial symptoms. Radical nephrectomy and renal hilar lymphadenectomy were performed. The tumor was 8 cm in greatest diameter; its cut surface was beige in color. Large metastasis to the renal hilar lymph node was identified. Histological examination of the right renal tumor met the criteria of chromophobe RCC. In addition to histological findings of typical chromophobe RCC, small cell foci, comedo-like necrosis, trabecular growth pattern, and sclerosing stroma were observed. However, no sarcomatoid foci were identified anywhere, despite extensive tumor sampling including lymph node lesions. Immunohistochemically, neoplastic cells were positive for E-cadherin and CD117 (c-kit). Ultrastructurally, tumorous cells contained abundant mitochondria and cytoplasmic microvesicles. Fluorescence in situ hybridization showed monosomy of chromosomes 2 and 10 and polysomy of chromosome 21. Finally, we suggest that this tumor may show the poorly differentiated or presarcomatoid form of chromophobe RCC.

Clear cell clusters in the kidney: a rare finding that should not be misdiagnosed as renal cell carcinoma.

Clear cytoplasm is a major characteristic feature of most malignant renal neoplasms. Benign clear cells in the renal parenchyma, usually histiocytes, can occasionally be found, but they are infrequently of an epithelial nature. We report histological, immunohistochemical, ultrastructural, and cytogenomic features of clear epithelial cell clusters incidentally found in four kidney specimens. Multiple microscopic clear cell clusters were present in the cortex, often in subcapsular location. They were composed of large epithelial cells with strikingly clear cytoplasm, without nuclear atypia, arranged in solid nests, and some tubules with narrow lumina. Immunohistochemically, they were positive for AE1AE3, PAX 8, EMA, kidney-specific cadherin, cytokeratin 7, E cadherin, and CD117, with focal immunoreactivity for CD10. Carbonic anhydrase IX, vimentin, and markers related to apoptosis and proliferation were negative. Ultrastructurally, the cytoplasms were enlarged and poor in organelles, showing ballooning degeneration. Array comparative genomic hybridization showed no chromosomal gains or losses. Clear cell clusters constitute a rare finding in the kidney and must be differentiated from benign lesions (ectopic adrenal tissue, osmotic tubulopathy, histiocytic clusters, renal adenomas) and renal cell carcinomas. Clear cell clusters appear to be generated from "endocrine-type" atrophic tubules whose cells are enlarged due to intracellular oedema. Immunohistochemistry shows a distal nephron phenotype with a limited expression of a proximal marker, CD10. Coexisting chronic renal disease or ischemic conditions seem to be related to the development of clear cell clusters. Pathological, ultrastructural, and cytogenomic features do not support a preneoplastic nature of this lesion, at least in the cases studied here.

Anticancer effects of CAMEL peptide.

This study analyzed whether therapy with CAMEL, an antimicrobial peptide (KWKLFKKIGAVLKVL), possess anticancer benefits. Although the peptide was cytotoxic for all the cell lines tested, it did not cause hemolysis, which suggests that CAMEL does not damage cell membranes. After cellular internalization, CAMEL localized to mitochondria and lowered the mitochondrial potential, resulting in the organelles' swelling, a decrease in cellular ATP level and, finally, cellular breakdown. High mobility group box 1 (HMGB1) protein, a necrotic death marker, was shown to be released from cells treated with CAMEL. Growth of B16-F10 melanoma tumors was clearly restrained after injections with CAMEL and could be kept in check throughout the period of peptide administration. However, if therapy was stopped, tumors started to grow again 3-4 days later. To reduce tumor volume and block tumor relapse, a combined therapy was required involving CAMEL and plasmid DNA carrying the interleukin-12 (IL-12) gene. The two therapeutic agents used in combination (a series of CAMEL injections first, followed by daily administration of plasmid DNA) delayed tumor growth and extended survival of treated animals in a statistically significant manner. Complete tumor regression was found in 60% of cases.

Use of electron microscopy in core biopsy diagnosis of oncocytic renal tumors.

The distinction between oncocytoma and chromophobe renal cell carcinoma, important clinically, may be challenging, especially as the tissue sample size decreases. Ancillary studies can be helpful, although subject to interpretation and sample variability. The aim of this study was to examine the value of electron microscopy in differentiating between oncocytoma and chromophobe renal cell carcinoma on formalin fixed paraffin embedded needle core biopsies. Twenty renal needle core biopsies were evaluated. Despite formalin fixation and paraffin embedding, the classic ultrastructural features of these neoplasms were retained, revealing 80% sensitivity and 100% specificity by initial work-up.

Mitochondria with tubulovesicular cristae in renal oncocytomas.

Renal oncocytoma and chromophobe renal cell carcinoma (CRCC) are closely related tumors. They are considered the extremes of a spectrum with several variants. Ultrastructural examination of the mitochondria is a helpful procedure in the diagnosis of these neoplasms. Renal oncocytomas show mitochondria with piled lamellar cristae, and CRCC exhibited mitochondria with tubulovesicular cristae. In a series of 23 histologically diagnosed renal oncocytomas examined by electron microscopy, the authors found 5 tumors exhibiting more cells with mitochondria showing tubulovesicular cristae. The authors believe these 5 cases present a submicroscopic appearance intermediate between renal oncocytoma and CRCC, although with benign clinical behavior.

Extracellular vesicle isolation from human renal cancer tissue.

Renal cell carcinoma is a lethal disease that is often discovered incidentally. New non-invasive biomarkers are needed to aid diagnosis and treatment. Extracellular vesicles (EVs), membranous vesicles secreted by all cells, are a promising potential source for cancer biomarkers, but new methods are required that are both sensitive and specific for cancer identification. We have developed an EV isolation protocol optimized for kidney tumor and normal kidney tissue that yields a high vesicle concentration, confirmed by nanoparticle tracking analysis (NanoSight) and by nanoscale flow cytometry (NanoFCM). Using Western blot, we confirmed presence of EV markers CD81, CD63, flotillin-1, and absence of cellular debris, calnexin. Transmission electron microscopy images demonstrate intact membranous EVs. This new method improves existing protocols with additional steps to reduce contaminants in the EV product. Characterization of our isolation product confirms successful isolation of EVs with minimal contamination. The particle yields of our protocol are consistent and high as assessed by both standard and novel methods. This optimized protocol will contribute to biomarker discovery and biological studies of EVs in renal cancer.

Proteomic identification of differentially expressed plasma membrane proteins in renal cell carcinoma by stable isotope labelling of a von Hippel-Lindau transfectant cell line model.

The von Hippel-Lindau (VHL) tumour suppressor gene plays a central role in development of clear cell renal cell carcinoma (RCC). Using a cell line pair generated from the VHL-defective RCC cell line UMRC2 by transfection with vector control or VHL (-/+VHL) and stable isotope labelling with amino acids in cell culture (SILAC) followed by enrichment of plasma membrane proteins by cell surface biotinylation/avidin-affinity chromatography and analysis by GeLC-MS/MS, VHL-associated changes in plasma membrane proteins were analysed. Comparative analysis of -/+VHL cells identified 19 differentially expressed proteins which were confirmed by reciprocal SILAC labelling. These included several proteins previously reported to be VHL targets, such as transferrin receptor 1 and the alpha 3 and beta1 integrin subunits and novel findings including upregulation of CD166 and CD147 in VHL-defective cells. Western blotting confirmed these changes and also revealed VHL-dependent alterations in protein form for CD147 and CD166, which in the case of CD166 was shown to be due to differential glycosylation. Analysis of patient-matched normal and malignant renal tissues confirmed these differences were also present in vivo in a subset of clear cell RCCs. These results illustrate the potential of this approach for identifying VHL-dependent proteins that may be important in tumorigenesis.

Characterization of membranous and cytoplasmic EGFR expression in human normal renal cortex and renal cell carcinoma.

Metastatic renal cell carcinoma (RCC) is highly resistant to conventional systemic treatments, including chemotherapy, radiotherapy and hormonal therapies. Previous studies have shown over-expression of EGFR is associated with high grade tumors and a worse prognosis. Recent studies suggest anticancer therapies targeting the EGFR pathway have shown promising results in clinical trials of RCC patients. Therefore, characterization of the level and localization of EGFR expression in RCC is important for target-dependent therapy. In this study, we investigated the clinical significance of cellular localization of EGFR in human normal renal cortex and RCC. RCC and adjacent normal kidney tissues of 63 patients were obtained for characterization of EGFR expression. EGFR protein expression was assessed by immunohistochemistry on a scale from 0 to 300 (percentage of positive cells x staining intensity) and Western blotting. EGFR membranous staining was significantly stronger in RCC tumors than in normal tissues (P < 0.001). In contrast, EGFR cytoplasmic staining was significantly higher in normal than in tumor tissues (P < 0.001). The levels of membranous or cytoplasmic EGFR expression in RCC tissues were not correlated with sex, tumor grade, TNM stage or overall survival (P > 0.05). These results showed abundant expression of membranous EGFR in RCC, and abundant expression of cytoplasmic EGFR in normal tissues. EGFR expression in RCC was mostly located in the cell membrane, whereas the EGFR expression in normal renal tissues was chiefly seen in cytoplasm. Our results suggest different locations of EGFR expression may be associated with human renal tumorigenesis.

Intracellular Na+:K+ ratios in human cancer cells as revealed by energy dispersive x-ray microanalysis.

Intranuclear sodium, potassium, and chloride contents were measured by energy-dispersive x-ray microanalysis in freeze-fractured, freeze-dried, bulk-tumor samples taken from 10 patients suffering from invasive urogenital cancers. Human biopsies were carried out during the first diagnostic interventions before any cytostatic treatment had been applied. Pathohistological diagnosis established the malignancy in each case. The cancers were classified in three types: keratinizing, transitional cell, and hypernephroid carcinoma. More than 250 cell nuclei were measured from each type of cancer. The results were compared with those obtained in intact human urothelium taken from patients having no malignant processes. Proximal and distal tubular epithelial cell nuclei representing the origin of human hypernephroid cancer were also measured in rat kidney because corresponding healthy human material cannot be obtained. The analyses revealed, in all three types of cancer cells, that the average intranuclear sodium content increased more than three-fold, the potassium content decreased 32, 16, and 13%, respectively; meanwhile the chloride content increased, but to a lesser extent than did the sodium. The intranuclear Na+:K+ ratios were more than five-fold higher in the cancer cells on the average, and their distribution histograms were much broader than in the normal human urothelium and in the tubular cell nuclei of the rat kidney. The results obtained fit well with the theory of Cone, C. D., Jr. 1971. J. Theor. Biol. 30: 151-181 according to which the sustained depolarization of the cell membrane may be of mitogenic effect.