A new method for flat-embedding large native cryostat sections for targeting small preneoplastic lesions in comparative ultrastructural and ultracytochemical investigations

Ultrastructural studies of rare and small cellular lesions in pathologically altered tissue are difficult to perform by applying conventional electron microscopic preparation. The search for lesions, often consisting of only a few cells in randomly obtained small specimen blocks, is time consuming and often without success. The methodological requirements for comparative enzyme cytochemical and morphological studies, i.e., preservation of both enzyme activity and ultrastructure, are divergent. By processing large native cryostat sections for electron microscopy, small preneoplastic focal lesions were successfully targeted in liver and kidney. Glucose-6-phosphatase, alkaline phosphatase, acid phosphatase, catalase, and cytochrome c oxidase activities were distinctly localized to endoplasmic reticulum, canalicular membrane, lysosomes, peroxisomes, and mitochondria, respectively, in the morphologically altered cells. Fixation of serial cryostat sections and enzyme reactions were both carried out through a semipermeable membrane except those for cytochrome c oxidase, which was demonstrated after fixation through the membrane by floating the section in incubation medium containing cytochrome c. Thereafter, the sections were flat embedded and polymerized between epoxy resin disks and aluminum dishes fitting exactly together. The objects of interest were identified in the light microscope, cut out, and reembedded in reversed gelatine capsules. By using this technique an ultrastructural preservation was achieved similar to that seen after immersion fixation. The enzyme activities were clearly localized without diffusion of the reaction product or unspecific deposits. The procedure permits precise targeting and complex studies of rare and small lesions, and opens new perspectives for the use of cryo-preserved tissue.

Cystic embryonal sarcoma of kidney: a case report

BACKGROUND

Morphologic analysis of malignant renal tumors of childhood and adolescence has resulted in the identification of a variety of tumor types with characteristic histology and clinical behavior. The authors report a case of renal sarcoma in a 19-year-old male that differs in morphology from the various established categories of primitive renal tumors.

METHODS

Sections taken from the nephrectomy specimen were stained by routine methods and by immunohistochemistry for stromal and epithelial markers, and for proliferation markers. In addition, ultrastructural studies were undertaken.

RESULTS

The tumor, which the authors termed cystic embryonal sarcoma, was comprised of poorly differentiated malignant mesenchyme in a myxoid stroma. Numerous epithelial-lined cysts were present. The distribution of the cysts and proliferation kinetics of cyst-lining epithelial cells suggested that they were derived from entrapped renal tubules. The tumor showed early recurrence postoperatively and after aggressive chemotherapy. The pathologic features and clinical behavior of the tumor resemble those of 2 previously reported cases and an additional 25 cases from the files of the National Wilms' Tumor Study Pathology Center.

CONCLUSIONS

The clinical and histologic features of cystic embryonal sarcoma differ from those of other renal tumors of childhood and adolescence, and the tumor appears to be a novel form of renal malignancy.

Carcinomalike monotypic epithelioid angiomyolipoma in patients without evidence of tuberous sclerosis: a clinicopathologic and genetic study

We report the clinicopathologic, immunohistochemical, ultrastructural, and genetic features of an unusual renal tumor composed of large, atypical, densely packed, clear/eosinophilic epithelioid cells. Three patients, two men and one woman (ages 31, 36, and 60 years of age, respectively), had abdominal pain. Morphologically, all cases showed aggressive features (largeness, atypical cells, sarcomatoid features, necrosis, and, in one case, invasion of the renal vein). Despite the marked morphologic resemblance of these tumors to high-grade sarcomatoid renal cell carcinoma, their phenotype (HMB45+, CD68+/-, actin+/-, and vimentin and keratin negative) is in contrast to that observed in epithelial tumors and parallels the phenotypic profile of angiomyolipoma. Ultrastructural analysis showed the presence of glycogen, mitochondria, and prominent electron-dense, membrane-bound granules in the neoplastic cells, and the absence of melanosomes or premelanosomes. Genetic study, performed using polymerase chain reaction from paraffin sections, showed a loss of heterozygosity at the TSC2-containing region on 16p in one case, and on 3p in two cases, showing that multiple genetic alterations are taking place in these tumors. Follow-up has shown local recurrence in one case after 6 years, and the patient died 1 year later of cardiorespiratory failure. The other two patients are well after 26 and 10 months. All three patients were evaluated for signs of tuberous sclerosis, and findings were negative. We suggest that these tumors should be considered close relatives of the angiomyolipoma variants, composed purely of perivascular epithelioid cells. More cases and longer follow-up durations are needed to fully evaluate its prognostic implication.

Pigmented microcystic chromophobe cell carcinoma: a unique variant of renal cell carcinoma

Five cases of pigmented chromophobe renal cell carcinoma are presented. The patients included four men and one woman between the ages of 60 and 73 years (median age, 66.5 years), who presented with symptoms due to their renal mass. Surgical resection of the renal mass was performed in all patients. Grossly, the tumors were well encapsulated, yellow to dark gray, with a vague nodular pattern on cut surface. The tumors varied between 2.5 and 9 cm in greatest diameter. Histologically, all tumors shared similar features, namely, a malignant cellular proliferation composed of deeply eosinophilic to clear cytoplasm with round nuclei and inconspicuous nucleoli. The cellular proliferation was arranged in a microcystic and/or microalveolar pattern. In one tumor, conventional areas of clear cell carcinoma in association with the chromophobe component were present. In addition, all tumors contained pigmented areas, which were shown by light microscopy to have features of lipochrome pigment. Ultrastructural studies of these areas demonstrated the presence of intracytoplasmic polygonal to round, electron-dense pigment granules, which in some areas seemed to coalesce to form larger granules. In addition, numerous mitochondria and cytoplasmic vesicles were present. The cases described herein highlight an additional morphologic variant of chromophobe renal cell carcinoma.

Renal small cell carcinoma (neuroendocrine carcinoma) without features of transitional cell carcinoma

Seventeen cases of renal small cell carcinoma have been reported in the literature. Approximately half of the reported cases show combined features of transitional cell carcinoma. Presented herein is a case of renal small cell carcinoma in a 37-year-old Japanese male who had been treated for 10 years with famotidine for duodenal ulcer. He suffered from sudden-onset chest pain at presentation and myxoma of the right atrium was suspected. He was treated by atriotomy and a tumor was removed from the right atrium and pulmonary artery. Histological examination, however, revealed it to be small cell carcinoma. Accordingly, a radical operation was performed for the removal of a tumor found in the right kidney. Histological examination of the tumor confirmed the presence of renal small cell carcinoma without any features of transitional cell carcinoma. It is reported that long-term administration of an histamine 2 (H2) receptor antagonist may produce carcinoid tumors in rodents and enterochromaffin-like cell hyperplasia in humans. The possible relationship between neuroendocrine carcinoma and H2 receptor antagonist therapy is discussed.

A case report of renal cell tumor in a 45-year-old female mimicking lower portion nephrogenesis

This report describes a renal tumor with an unusual histology in a 45-year-old woman. The tumor was white in color, different from usual renal cell carcinoma, and mainly consisted of variously shaped tubules formed by flat or cuboid cells within marked edematous stroma. Elaborated branching or tubules arranged in a papillary pattern with focal spindle-shaped cell proliferation were characteristic features. Immunohistochemical staining expressed diffusely positive for vimentin and S-100 protein, partially positive for cytokeratin and epithelial membrane antigen and negative for Leu-M1, Leu-7, CD34 and markers for muscle cells. Ultrastructural studies of the tumor cells showed adenocarcinoma-like characteristics. According to these histological, immunohistochemical and electron microscopy findings, it is suggested that this tumor be designated as unclassified renal cell carcinoma with histology mimicking lower-nephron nephrogenesis.

Metanephric adenoma of the kidney. A clinicopathologic, immunohistochemical and electron microscopic study of two cases

We report two cases of metanephric adenoma in 40 and 48 year-old women. These rare kidney tumors were composed of cuboidal epithelial cells forming tubules, glomeruloid structures and sheets. Ultrastructural and immunohistochemical studies revealed that the tumor cells are similar to epithelial cells of developing nephrons. These features differentiate the metanephric adenoma from tubulo-papillary renal carcinoma, nephroblastoma, and cortical adenoma. According to its invariably benign course, the metanephric adenoma treatment could be restricted to a simple tumorectomy.

Expression patterns of the ectopeptidases aminopeptidase N/CD13 and dipeptidyl peptidase IV/CD26: immunoultrastructural topographic localization on different types of cultured cells

Aminopeptidase N/CD13 and dipeptidyl peptidase IV/CD26 are widespread membrane-bound peptidases involved in fundamental biological processes. Using cryo-ultramicrotomy of cultured cells followed by indirect immunogold labelling, both enzymes appeared to be strongly and regularly labelled on the cell surfaces of human synovial fibroblasts, T-lymphocytes and colon carcinoma cells Caco-2. In the cytoplasm of the synovial fibroblasts gold-labelled vesicle-like structures were found, which we consider to be potential transport vesicles. An abundant and regular expression of CD13 was detected on cultured renal parenchymal cells. On the renal carcinoma cell line Caki-1 cells we found a low, non-homogeneous and clustered CD13-labelling. On cultured renal parenchymal cells and the Caki-1 cells CD26 could not be observed. The expression pattern of CD26 on renal carcinoma cell line Caki-2 cells showed also a slightly clustered distribution. A low density CD26-labelling was present on the squamous cell carcinoma cell line UM-SCC-22B. CD13 was absent in Caki-2 and UM-SCC-22B cells. The presence of both enzymes on the cultured cells enables their ultrastructural investigation under different growth conditions and their involvement in cell-cell interactions. For this purpose, however, further investigations are necessary.

Sublethal alterations and sustained cell proliferation associated with the diethylstilbestrol-induced renal carcinogenesis in male Syrian golden hamsters

The current study was initiated to explore the sublethal alterations and the tissue damage occurring in the hamster kidney during diethylstilbestrol-induced renal carcinogenesis. A total of 49 male Syrian golden hamsters (35 treated and 13 control animals) was utilized in the experimental procedure. Chronic exposure to diethylstilbestrol was achieved by s.c. insertion of implants containing 25 mg diethylstilbestrol. For long-term observation, adequate blood level of diethylstilbestrol was insured by renewing the implant every 2 months. Experimental groups (n = 4 to 9) were terminated 1, 2, 4, 6, 9 and 11 months after initial implantation for morphological examination of the kidney. Diethylstilbestrol carcinogenicity in this experimental model was confirmed by the observation that most animals undergoing drug exposure for 6 months or more exhibited renal neoplasms. The most striking nonneoplastic morphological abnormality disclosed by histological and cytological examination consisted in the accumulation of granular inclusions in proximal tubule cells. In renal tissue, the extent of cell proliferation determined by PCNA labeling progressively increased along with the duration of diethylstilbestrol exposure and suggested a sustained proliferative response in altered proximal tubules. The present data suggest that an impairment of functional tubular regeneration could promote, as well as the estrogen genotoxic effect, the tumorigenicity of diethylstilbestrol in the kidney of male hamsters.

Cellular dysplasia in acquired cystic renal disease: comparison of histomorphometrically gauged nuclear parameters in normal kidneys, renal cell carcinomas and acquired cystic kidneys

Nuclear parameters were assessed by computer-assisted image analysis in the cells of abnormal epithelial formations in the acquired cystic kidneys of two dialysis patients, the proximal and distal tubules of a normal kidney and two well differentiated renal cell carcinomas. One acquired cystic kidney contained many small clear celled foci and am 0.9 cm-size clear celled lesion and the second one a papillary microadenoma. The clear celled lesion was cytologically indistinguishable from the carcinomas. The histomorphometrically gauged nuclear parameters were maximal and minimal ferret diameters, averaged ferret diameter, aspect ratio, shape factor, area, volume and specific length and width. Statistical evaluation evidenced that the nuclear area, volume, aspect ration and shape factor allowed for the distinction between benign and malignant epithelial structures. The medians of the nuclear parameters of atrophic tubules, cysts, clear celled foci, papillary adenoma and clear celled lesion in the two acquired cystic kidneys deviation from those of normal renal tubules and in, increasing order of disparity, approached those of the carcinomas.

Glassy hyaline globules in granular cell carcinoma, chromophobe cell carcinoma, and oncocytoma of the kidney

The presence of glassy hyaline globules (GHG) in renal carcinomas has been rarely emphasized in the literature. We studied the frequency of these globules in numerous renal carcinomas, including granular cell, mixed clear cell/granular cell, papillary renal cell, and chromophobe renal cell carcinoma, as well as oncocytomas. GHG are eosinophilic bodies in the hematoxylin-eosin stained sections with a size ranging from 1 to 30 micrometer and strongly positive with the periodic acid-Schiff (PAS) histochemical stain. Ultrastructurally, they are seen as amorphous secretion inside of the cisternae of the rough endoplasmic reticulum. GHG were found in 49 of 64 cases of granular cell and mixed clear cell/granular cell renal carcinomas and in 5 of 33 papillary renal cell carcinomas. No GHG were found in 22 cases of chromophobe cell carcinomas and 26 renal oncocytomas. Our findings suggests that GHG are a characteristic feature of granular cell carcinomas, mixed clear cell/granular cell renal carcinomas, and in a small minority of papillary renal cell carcinomas. In addition, it suggests that the presence of GHG in a renal cell tumor may be of aid for excluding a diagnosis of chromophobe cell carcinoma or oncocytoma.

Collecting duct carcinoma of kidney

Collecting duct carcinoma of the kidney is a rare neoplasm with only approximately 100 cases described in the literature to date. The tumor occurs in a wide age range and predominantly in males. Typical collecting duct carcinoma consists of a grossly infiltrative neoplasm centered on the renal medulla. The usual histological pattern is that of a tubular or tubulopapillary carcinoma with a desmoplastic stroma that often contains neutrophils. Less commonly, collecting duct carcinoma has a papillary architecture with desmoplasia and infiltrative growth. Collecting duct carcinoma spread aggressively and many patients have metastases at the time of presentation. Origin in the collecting duct is suggested by medullary location, dysplasia of the epithelium in collecting ducts outside the tumor, and reactivity with antibody to high molecular weight cytokeratin and Ulex europaeus agglutinin. No unifying cytogenetic or molecular genetic features have been discovered thus far. The concept of collecting duct carcinoma is expanding and should include the recently described renal medullary carcinoma that is associated with sickle cell trait.

Extensively cystic renal neoplasms: cystic nephroma, cystic partially differentiated nephroblastoma, multilocular cystic renal cell carcinoma, and cystic hamartoma of renal pelvis

Predominantly cystic renal neoplasms have been the source of diagnostic confusion and controversy. In this review, the authors analyze the clinical and pathological features of four entities that consistently exhibit a diffusely cystic growth pattern, are strikingly similar in their gross appearances, and are not separable by preoperative imaging studies. Based on the literature, this review concludes that tumors in young children that have been classified as cystic nephroma and cystic partially differentiated nephroblastoma likely represent a single entity, and all should be considered highly cystic Wilms' tumors with little or no capacity for invasion or metastasis and diagnosed as cystic partially differentiated nephroblastoma. Conversely, cystic nephroma in adults has no discernible connection with Wilms' tumor or nephrogenic rests and should be considered a benign composite neoplasm of stroma and epithelium of unknown histogenesis, which may rarely become malignant with secondary development of a sarcoma. Multilocular cystic renal cell carcinoma appears to be unrelated to cystic nephroma and if the following criteria are met, it appears to be a neoplasm with an intrinsically cystic growth pattern, and no, or at most little, malignant potential: (1) an expansile mass is surrounded by a fibrous wall, (2) the interior of the tumor entirely is composed of cysts and septa with no expansile solid nodules, and (3) the septa contain aggregates of epithelial cells with clear cytoplasm. Cystic hamartoma of the renal pelvis is a rare, complex tumor composed of stroma with a prominent smooth muscle component and a variety of epithelial elements.

Chromophobe renal cell carcinoma: clinicopathological study of 7 cases

Chromophobe renal cell carcinoma (CRCC) may be grossly and microscopically confused with oncocytoma. It is now believed that many, if not all, of the so-called malignant oncocytomas or oncocytomas with metastases reported in the literature were indeed chromophobe renal cell carcinomas. CRCC is characteristically positive for colloidal iron and shows cytoplasmic microvesicles in electron microscopy. This study of CRCC is thought to be the first one done in Latin America. Of a total of 106 renal epithelial neoplasms, 7 (6.6%) fulfilled the criteria for chromophobe renal cell carcinoma. This frequency in Brazil is similar to that in other parts of the world. There was no difference in age, sex, and race distribution of CRCC compared to usual renal epithelial tumors. Grossly, the CRCC ranged in size from 3.5 to 20 cm (average: 10.2 cm) in greatest dimension. Most frequently, the tumor was brown on the cut surface. The growth pattern showed compact areas in all tumors and, in most of the cases, both clear and eosinophilic cellular subtypes were seen. The electron microscopic findings favor an origin of the microvesicles from outpouchings of the outer membrane of mitochondria. The strong positivity for colloidal iron in spite of the destruction of the cytoplasmic vesicles in paraffin-embedded specimens seems to indicate that the acid mucopolysaccharides are not located inside the microvesicles. By the time of diagnosis, only one case had regional lymph node metastases and this particular case was the only one mixed (associated with the usual renal cell carcinoma). The follow-up examination after nephrectomy showed that prognosis seems to be favorable in CRCC, except when the tumor coexists with the usual renal cell carcinoma.

Low-grade spindle cell carcinoma of the kidney

The authors report a renal cell carcinoma composed largely of spindle cells of Fuhrman's nuclear grade II in which the bland appearance of the cells and low mitotic index were reminiscent of a benign or low-grade smooth muscle tumor. Keratin immunostaining was positive, but evidence of epithelial differentiation was obtained by electron microscopy. The tumor was an incidental finding and it did not invade the perirenal fat or the renal vein. Follow-up is only 24 months but the histological features suggest that the prognosis may be better than that of a classic sarcomatoid renal cell carcinoma.

[Electron microscopic study of capillary in the human renal cell carcinoma]

PURPOSE

In this study, we investigated the ultrastructure of the microvasculature in human renal cell carcinoma (RCC) specimens.

MATERIALS AND METHODS

RCC specimens from 30 patients were studied by light microscopy after hematoxylin and eosin staining and alpha-smooth muscle actin staining, and by electron microscopy after uranyl acetate lead nitrate staining or periodic acid thiosemicarbazide gelatin methenamine silver staining.

RESULTS

In the light microscopy, the capillaries located adjacent to the renal medullary tubules in normal renal tissue specimen were in an orderly manner, while capillaries in the RCC specimens were found to be densely or sparsely distributed unconventionally. The pericytes encircling the capillary endothelial cells were positive for alpha-smooth muscle actin and formed aggregates in many of the RCC specimens, but did not form aggregates in the normal tissue specimens. In the electron microscopy, capillary endothelial cells in the normal renal tissue specimens were found to form well-developed membranous structure such as characterized by fenestrations and tight junctions. However, few pericytes were detected. On the other hand, the capillary endothelial cells in RCC specimens were found to be immature with poorly developed junctional complexes. Capillary pericytes with numerous cytoplasmic processes were found in many of the RCC specimens. In addition, the basement membranes of the capillary walls were structurally abnormal in that it was being multilayered. Based on the results of analysis of a total of 324 capillaries observed in all RCC specimens, capillaries could be classified as type I capillaries, associated with well-developed pericytes with numerous processes, or type II capillaries, associated with few pericytes with few processes. Type I capillaries predominated in cases which an angiographically hypervascularity was detected. Whereas, type II capillaries predominated in cases in which angiographically hypovascular pattern were detected.

CONCLUSION

The fine structure of the pericytes seems to reflect the qualitative difference in capillary structure between normal renal tissue and RCC specimens. Therefore, the present findings may contribute to the recognition of intratumoral hemodynamics.

Bellini duct carcinoma of the kidney--a case report

Bellini duct carcinoma (BDC), originating from the principal cells of the collecting duct of the kidney, accounts for only 1% of renal carcinomas. This lesion is a histogenetically, morphologically and cytogenetically defined entity. We report an eosinophilic variant of BDC. A 71-year old male presented with a tumor in the right kidney. Nephrectomy was performed. BDC (stage pT3a N0 M0 G2, based on UICC classification) was diagnosed. Electron microscopy revealed an abundance of mitochondria. Intranuclear rodlets were seen. Neuroendocrine differentiation was not demonstrated. After a three-year observation period, there are no signs of recurrence or metastases.

Diagnostic significance of mitochondria in four types of renal epithelial neoplasms: an ultrastructural study of 60 tumors

Mitochondrial morphology was studied in 60 renal epithelial neoplasms, including clear cell, papillary, chromophobe cell, and oncocytomas, to see if there are significant differences among the various subtypes. Mitochondria from the nephron tubular system obtained from 36 patients with glomerular diseases served as controls. Significant differences were found in mitochondrial ultrastructure in each of the subtypes of renal epithelial tumors. Novel observations were the presence of tubulovesicular cristae in many of the mitochondria found in chromophobe cell renal carcinomas and the discovery of a possible new oncocytic variant of this entity with mitochondria with pseudotubulovesicular and lamellar cristae similar to those of renal oncocytomas. This latter finding may be of prognostic significance, since renal oncocytomas are benign, while chromophobe cell neoplasms may behave in a malignant fashion.

Pigmented renal cell carcinoma: accumulation of abnormal lysosomal granules

AIMS

Five cases of renal cell carcinoma (RCC) with abnormal pigmentation have been examined by histochemical, immunohistochemical and ultrastructural methods.

METHODS AND RESULTS

Compared with conventional RCCs, there was no difference in histological findings of each case, except for the presence of pigmented cells. In three cases, tumour cells possessing various sized brown granules with neuromelanin-like features were scattered throughout the tumour. The granules observed in one of the others were angulated lysosomes and in another tumour cells in the pigmented areas possessed the granules closely resembling those of granular cell tumour. However, melanosome or neurosecretory granules could not be detected in any of the cases examined. In three cases, some of these abnormal granules showed a weak acid phosphatase activity. On immunohistochemical examination, tumour cells showed a positive immunoreaction for epithelial markers and lacked any antigens suggesting neuroectodermal or neuroendocrine differentiation. The granules in three cases were faintly positive for lysozyme and KP-1.

CONCLUSIONS

These findings indicate that abnormal pigmentation of RCCs examined in this study is attributed to accumulation of abnormal lysosomal granules in the neoplastic cells.

[New contributions to the study of chromophobe-cell renal carcinoma]

OBJECTIVE

The present study describes a case of the recently discovered chromophobe cell carcinoma of the kidney. Additional findings that have not been previously reported are presented and the importance of the clinical and anatomopathological diagnosis of this tumor type is underscored.

METHODS

The tumor presented in a 72-year-old female with symptoms and signs that were not distinct from those of other more common renal tumors. She underwent a right radical nephrectomy. Histopathological, immunohistochemical and ultrastructural studies were performed and the findings were compared with those reported in the literature.

RESULTS

The foregoing studies disclosed a chromophobe cell renal carcinoma, with some findings-chiefly ultrastructural-that have not been previously described.

CONCLUSION

Chromophobe cell renal carcinoma, a tumor type that has recently been identified, is the subject of several studies that have been conducted to permit its clinical and anatomopathological characterization. The present study describes some observations which, to our knowledge, have not been previously described elsewhere.

Juxtaglomerular cell tumor of the kidney: report of a non-functioning variant

A case of a juxtaglomerular cell tumor (JCT) in a 46-year-old man is reported. The tumor, 2.4 cm at its greatest dimension, was incidentally detected by ultrasonography. Although histological, immunohistochemical, and electron microscopic examinations revealed typical features of a JCT, the patient had no history of hypertension or hypokalemia. This is the first report of a non-functioning JCT in the literature.

Fine-needle aspiration of chromophobe renal cell carcinoma. Analysis of six cases

BACKGROUND

The chromophobe variant of renal cell carcinoma is a recently described and frequently unrecognized tumor. Because the prognosis of the chromophobe variant appears to be intermediate between that of oncocytoma and the clear cell variant of renal cell carcinoma, accurate diagnosis may be important for appropriate clinical management.

METHODS

A retrospective analysis of fine-needle aspirations of four primary and two metastatic chromophobe renal cell carcinomas (five typical and one eosinophilic variant) with histologically confirmed primary tumors was performed. Hale's colloidal iron stain was strongly positive in a diffuse cytoplasmic pattern in all resected primary tumors.

RESULTS

All fine-needle aspirations were characterized by cellular smears comprised of single cells and small groups of cells. The cytoplasm varied from granular to flocculent. A characteristic feature was the presence of occasional markedly enlarged, bizarre, often multinucleated cells, within a background of moderately atypical cells. Nuclear enlargement, hyperchromasia, pleomorphism, and outline irregularity were noted in all cases. These features imparted a koilocyte-like appearance to many of the cells. Intranuclear pseudoinclusions were present in four cases and were numerous in two.

CONCLUSIONS

Both primary and metastatic chromophobe renal cell carcinomas have unique cytologic features that allow for their distinction from oncocytoma and other variants of renal cell carcinoma.

Hyaline globules in renal cell carcinomas and oncocytomas

Hyaline globules (extracellular collections of amorphous material) are identified in 10 of 59 renal cell carcinomas (RCC) and in 2 of 9 oncocytomas. Immunohistochemical characterization of these PAS-positive structures revealed the presence of basement membrane material in most cases. Collagen type IV and laminin were the predominant constituents, whereas fibronectin was detected only occasionally. Electron microscopic examination of the globules showed concentric multilayered accumulations of basement membrane material. No such structures were recognized in 8 renal pelvic transitional cell carcinomas nor in 2 metanephric adenomas. RCC associated hyaline globules were always negative for alpha1-antitrypsin (AAT), alpha-fetoprotein (AFP), amyloid A, cytokeratin, vimentin, or lysozyme. These features differ from those of the hyaline globules previously described in other malignant neoplasms, notably AAT-positive hyaline globules in ovarian tumors, and AFP-positive globules in yolk sac tumors. Identification and immunohistochemical characterization of hyaline globules in metastases may be helpful in determining the origin of occult primary tumors.

Juxtaglomerular cells tumor of the kidney: a case report with electron microscopic and flow cytometric investigation

A juxtaglomerular cell tumor (JGCT) was found in the right kidney of a 17-year-old female who had suffered from a headache of 1-year duration and hypertension. CT and US were diagnostic in association with determination of plasma renin activity. Light and electron microscopic, immunohistochemical, and flow cytometric investigation of the resected tumor confirmed the diagnosis of JGCT with demonstration of ultrastructural features and distribution pattern of characteristic secretion granules of various sizes and shapes, coexistence of mast cells within the tumor (JGCT cells/mast cells = 10), and perivascular architecture.

Ultrastructure of streptozotocin-induced renal tumours in mice

Streptozotocin-induced tumours in the kidneys of experimental animals have been shown to be histologically similar to human renal cell carcinoma. We report the ultrastructural features of renal tumours induced in 15 mice by a single intravenous bolus of 2.5% streptozotocin administered in a dose of 250 mg streptozotocin/kg mouse body weight. Animals were sacrificed 232-361 days after the administration of streptozotocin. On examination both kidneys from each animal contained 1-4 dysplastic tubules and 1-3 discrete tumours per kidney. Twelve dysplastic proximal convoluted tubules showing varying degrees of epithelial atypia and nine tumours exhibiting either a papillary or solid architecture were examined. Dysplastic epithelial cells and tumours of papillary and solid type exhibited complex cell borders with well-developed junctional complexes. The majority of cells contained surface microvilli, and in some cells microvilli-lined intracytoplasmic lumina were observed. Occasional dysplastic epithelial cells and tumour cells contained double-membrane vesicles 120-200 nm in diameter. These were similar to the intracytoplasmic vesicles characteristic of human chromophobe renal cell carcinoma. Intracytoplasmic collections of glycogen granules and flocculant protein were identified in both dysplastic and neoplastic cells, and where prominent they resulted in compression of cytoplasmic organelles. Coated vesicles were commonly observed. These were free within the cytoplasm and were also seen budding from strands of rough endoplasmic reticulum. The distribution of these vesicles suggested a role in protein transport from the rough endoplasmic reticulum. It is concluded that while streptozotocin-induced renal tumours have some ultrastructural features in common with human chromophobe renal cell carcinoma, the overall ultrastructural morphology differs significantly from that described for the various histological types of human renal cell carcinoma.

Diagnosis and management of malignant perirenal schwannoma

Malignant retroperitoneal schwannoma is an extremely rare tumor, with only six cases previously reported occurring in the perirenal space. We herein report the seventh case. A 50-year-old woman presented with an abdominal mass suggestive of renal cell carcinoma by standard preoperative evaluation. The tumor required surgical exploration and pathologic evaluation for diagnosis. The final histologic diagnosis was made with the aid of electron microscopy and immunohistochemical staining with antibodies for S-100 protein.

[Multicystic renal dysplasia and Wilms tumor]

We review a case of multicystic right dysplasia containing nodular renal blastema in a 3-year-old girl with left Wilms tumor. In relation to this finding the management of the asymptomatic multicystic dysplastic kidney in discussed.

The t(1;12)(p36;q13) in a renal oncocytoma

A new chromosome rearrangement, t(1;12)(p36;q13), is added to the cytogenetic changes found in renal oncocytomas. The breakpoint in 12q is cytogenetically different from those of the MAR region, and molecularly HMGIC located in 12q15 on the basis of 3' RACE experiments does not seem to be directly involved.

Metanephric adenoma of the kidney: ultrastructural, immunohistochemical and lectin histochemical studies

A case of metanephric adenoma, a rare benign tumor of the kidney is reported, and the results of ultrastructural, immunohistochemical, and lectin histochemical studies are presented. The patient was a 47 year old Japanese man presenting with a left renal tumor by ultrasonography. The nephrectomy material revealed a well-demarcated tumor with medullary appearance, and on histological examination the tumor was composed of cuboidal cells forming regular small tubules with hyalinous stroma. Incomplete glomeruloid structures were formed in a few elongated tubules composed of columnar cells. Metanephric blastema was not observed in the tumor or in the normal kidney. By electron microscope, the tumor cells were observed to be immature cells with microvilli at the apical surfaces. The neoplastic tubules were surrounded by basal lamina. The tumor cells were immunoreactive for Leu 7, epithelial membrane antigen, vimentin, and low molecular weight cytokeratin, and were weakly immunoreactive for S-100 protein. Peanut agglutinin, soybean agglutinin, and Dolichos biflorus agglutinin were bound to the apical surfaces of the tumor cells.

Ultrastructure of cellular congenital mesoblastic nephroma

A detailed ultrastructural description of the cellular variant of congenital mesoblastic nephroma (CMN) is presented and compared to the classical form. Studied were 9 cases of the cellular variant, 6 mixed (cellular/classical) tumors, and 1 classical CMN. The occurrence of a broad selection of ultrastructural features was assessed using a semiquantitative scoring system. The results indicate that cellular CMNs are composed mainly of primitive mesenchymal cells, but also usually contain varying numbers of differentiating fibroblasts and myofibroblasts. This entity thus bears a closer resemblance at the ultrastructural level of organization to infantile fibrosarcoma than to conventional fibrosarcoma. Electron microscopy can be useful in distinguishing this relatively benign entity from the several malignancies with which it is sometimes confused.

Ultrastructural evaluation of renal cell oncocytomas

The utility of ultrastructural evaluation of eosinophilic renal cell neoplasms is illustrated by two case studies. The differential diagnosis between granular renal cell carcinoma and renal cell oncocytoma may be difficult. Ultrastructural demonstration of the presence of abundant mitochondria is useful in the definitive diagnosis of fine-needle aspiration specimens, those neoplasms with nuclear pleomorphism, or in patients requiring renal parenchymal sparing surgery.

A comparison between histological grade and nuclear morphometry for predicting the clinical outcome of localized renal cell carcinoma

OBJECTIVES

To determine the interrelationship of histological grade and nuclear morphometry and to compare their prognostic significance in patients with localized renal cell carcinoma (RCC).

PATIENTS AND METHODS

A retrospective prognostic study of 39 patients with localized (pT1, pT2) RCC was performed. Conventional histological grade and nuclear morphometry were assessed independently and the correlation between these grading systems and their impact on the patients' outcome were evaluated.

RESULTS

Histological grade and the nuclear morphometric variables were significantly correlated: the strongest association was that between grade and the nuclear regularity factor. The best predictor of disease-free interval and survival (by univariate analysis) was the combination of nuclear area and nuclear elongation factor, followed by conventional tumour grade, nuclear elongation factor, nuclear regularity factor and nuclear area. However, a multivariate analysis showed that the only independent prognosticator for survival was the combination of nuclear area and nuclear elongation factor.

CONCLUSIONS

This study indicates that nuclear morphometry is prognostically superior to histological grade in patients with localized RCC.

Overexpression of the met/HGF receptor in renal cell carcinomas

The c-met oncogene encodes the receptor for hepatocyte growth factor/scatter factor (HGF/SF), a multifunctional cytokine able to mediate morphogenesis as well as mitogenesis, motogenesis and invasiveness of epithelial cells. HGF/SF has been implicated in branching tubulogenesis of the developing kidney and in regeneration after renal injury and nephrectomy. We have examined the expression of the met/HGF receptor in normal human kidney and tissues of the genito-urinary tract, and in 50 kidney neoplasms of different histotypes, using monoclonal antibodies (MAbs) against the met/HGF receptor and immunohistochemistry. In normal kidneys, weak staining restricted to the distal tubules was observed. Transitional cell carcinomas were consistently negative, whereas increased expression at various levels was found in 87% of renal cell carcinomas with different cytological features and histological patterns. Western blot analysis of samples showed that the met/HGF receptor found in the malignant cells exhibits features of the normal receptor. The met/HGF receptor is also overexpressed in a renal cell carcinoma cell line, whose motility is triggered by HGF/SF. Our data suggest that expression of the met/HGF receptor may be involved in the onset and progression of renal cell carcinomas.

Establishment of two human renal cell carcinoma cell lines with different chemosensitivity

Two cell lines, SKR1 and NKK1, were established from renal cell carcinomas (RCC) with different histopathologic characteristics: SKR1 from grade 3, solid type, pleomorphic cell type carcinoma in a 66-year-old male and NKK1 from grade 2, alveolar type, clear cell carcinoma in a 49-year-old female. Electron microscopic study showed the presence of microvilli on cell surface and desmosome-like structures between cells in both lines. Doubling time and plating efficiency of SKR1 were 28 h and 37%, respectively, whereas those of NKK1 were 45 h and 22%, respectively. The chromosome number of both cell lines was 100% aneuploid with a mode of 74 chromosomes for SKR1 and 84 for NKK1. Both SKR1 and NKK1 induced tumors at the site of subcutaneous injection of nude mice. The morphologic characteristics of the tumor were similar to those of each original tumor. NKK1 was about 20 times more resistant to doxorubicin and vinblastine as compared to SKR1. Expression of P-glycoprotein was considered to be one of the factors responsible for such multidrug resistant phenotype of NKK1 cells. These two lines with different chemosensitivity may be a useful model for developing new therapeutic strategies for RCC.

Immunohistochemical and cytogenetic findings in malignant rhabdoid tumor

BACKGROUND

The histogenesis of malignant rhabdoid tumor (RT) remains a matter of controversy. From published reports it appears that some extrarenal RT (ERRT) exhibit neural or neuroectodermal features. Systematic investigation of renal RT (RRT) for neural differentiation has not yet been published. In this study, two RRT and two ERRT were investigated by light and electron microscopy, immunocytochemistry, and cytogenetic analysis.

RESULTS

All four cases exhibited similar morphology and a largely consistent immunohistochemical staining profile. Both tumor types showed immunoreactivity for various cytokeratins, epithelial membrane antigen (EMA), vimentin, neurofilaments, S100 protein, neuron specific enolase, Leu7, CD34, p53, MB2, MIC2, VS38c, laminin and fibronectin. Reactivity was usually confined to a small proportion of the tumor cells, especially in the case of antibodies against neurofilaments, NSE, S100 proteins Leu7, CD34 and p53. Only a few of the antibodies (anti-vimentin, MB2, MIC2, anti-EMA, and VS38c) stained the majority of the tumor cells. Chromosome analysis revealed a discrete aberration in 11p (most probably a paracentric inversion in 11p15) in the one RRT investigated. One ERRT had a normal karyotype, but the other one exhibited various structural abnormalities on chromosomes 18 and 22.

CONCLUSIONS

The immunohistochemical investigations revealed many similarities between RRT and ERRT, and all four tumors investigated exhibited neuroectodermal differentiation. As far as histogenetic classification is concerned, our findings point in the direction of the group of tumors that includes Ewing's sarcoma and primitive neuroectodermal tumors.

Renal oncocytoma. Pathological evaluation and clinical implications

Renal oncocytoma is a benign tumour of renal tubular origin; oncocytes are transformed epithelial cells rich in mitochondria, probably representing senescent degenerative cellular changes. Most of renal oncocytomas usually follow a benign clinical course and partial nephrectomy or enucleation has been advocated as curative. By immunohistological staining of tissue sections using monoclonal antibodies (DBA, SBA, PNA, UEA, Cytocheratine), we can suppose the histogenetic origin of renal oncocytomas from a region other than the proximal tubular epithelium, and in particular from the collecting duct epithelium. We believe that it is most important to perform flow cytometry to study the chromosomal pattern of the tumour, once intra-operative frozen sections have advanced the suspicion of renal oncocytoma; if oncocytic cells show a diploid pattern, and the tumour mass is well circumscribed and has not an excessive diameter, we favour renal sparing surgery.

Metanephric adenoma: histology, immunophenotype, cytogenetics, ultrastructure

Metanephric adenoma is a rare renal neoplasm that is histologically and clinically unique. We found this neoplasm in a 54-year-old woman. This large, well-circumscribed, solid, tan tumor showed histologic similarity to developing metanephric tubular epithelium. It is composed of uniformly small epithelial cells forming tubules. Immunohistochemical evaluation showed that the tumor cells express proximal tubule marker URO-2 and wt1 gene protein product, commonly expressed in Wilms' tumors. Ultrastructurally, the epithelial cells were characterized by the presence of cilia on the luminal side and were resting on an abundant basement membrane. Cytogenetic analysis showed normal female karyotype. The unique features of metanephric adenoma should be clinically and pathologically recognized because of its invariably benign course.

Primary small cell neuroendocrine carcinoma of the kidney

The histological, immunohistochemical, and ultrastructural features of a primary small cell neuroendocrine carcinoma of the renal parenchyma are described. Tumor cells were positive for cytokeratin, neuron-specific enolase, and Leu 7, but Grimelius- and chromogranin-negative. They also exhibited positivity with anti-MIC2 antibody. By electron microscopy, tonofibrils, primitive desmosomes, and dense-core granules with a neuroendocrine appearance were present. This is only the 7th recorded example of such a tumor at this site, which showed an aggressive course characterized by widespread bony metastases.

A nude mouse Wilms' tumor line (KCMC-WT-1) derived from an aniridia patient with monoalleleic partial deletion of chromosome 11p

BACKGROUND

A candidate tumor suppressor gene, WT-1, is believed to have an important role in the pathogenesis of Wilms' tumor, especially that occurring in patients with congenital aniridia.

METHODS

To obtain a stable tumor line to work with, Wilms' tumor tissue was serially transplanted in athymic nude mice. Biopsied Wilms' tumor tissue, derived from an aniridia patient, was transplanted subcutaneously to an athymic nude mouse, and then transplanted serially. Histopathologic and molecular biologic studies were performed on the xenotransplants.

RESULTS

The aniridia patient showed partial deletion in one short arm of chromosome 11, which bears the WT-1 gene. The tumor was successfully transplanted in the nude mouse. Although the tumor contained blastemic, organoid, and stromal histologic elements, the organoid element began to decrease after more than 20 passages. Cytogenetic analysis revealed an additional abbreviation of one long arm of chromosome 6. Dot blot analysis showed that the copy number of WT-1 gene was decreased to half the amount in the tumor, in spite of the WT-1 transcript with normal size detected by Northern blotting.

CONCLUSIONS

The tumor is expected to bear one WT-1 gene with minute abnormalities as well as one congenitally deleted gene. This tumor line is useful when examining the effect caused by introduction of WT-1 gene to Wilms' tumor in vivo.

[Renal cell carcinomas in children. Apropos of two cases]

The authors report two cases of renal cell carcinoma in children. A tumor occurring in a eight-year-old girl was composed of granular and oncocytic cells with obvious nuclear atypia. The other renal neoplasm, occurring in a nine-year-old boy, had a papillary pattern and was composed of small cells with mild nuclear atypia. In both patients, the tumor was confined to the kidney; radical nephrectomy was performed and patients were free of disease-with a follow-up of four years and one year, respectively.

[Electron microscopic analysis of eosinophilic renal cell carcinoma]

Renal cell carcinoma with cytoplasmic eosinophilic globules visualized on routine histologic preparations was analyzed. Eosinophilic globules in cytoplasm of the cells in renal cell carcinoma are very rate and till today we have not heard or found in the literature an attempt to analyze and describe them and that was the aim of our study. By electron microscopy, the globules most closely resembled non-membrane bound filamentous material that normally constitutes the cytoskeleton of normal and neoplastic renal epithelium.

Comparison of ureteropelvic transitional cell carcinoma with bladder transitional cell carcinoma using an image analyzer

To elucidate whether a significant difference in malignant potential between ureteropelvic transitional cell carcinoma (TCC) and bladder TCC is present, the argyrophilic nucleolar organizer region (AgNOR), nuclear DNA content and mean nuclear area (MNA) were evaluated in 32 ureteropelvic TCCs and 60 bladder TCCs, and were also compared with histological grade and stage. The parameters used were the mean AgNOR count (C-AgNOR), the percentage of cells exhibiting more than 3 AgNOR dots within nuclei (P-AgNOR), 2c deviation index (2cDI), 5c exceeding rate (5cER) and MNA. No significant difference in these 5 parameters was found between ureteropelvic and bladder TCCs. In addition, within each histological grade of tumor, no significant difference in each parameter between ureteropelvic and bladder TCCs was noted. Similarly, within pTa or pT1 TCCs, there was no significant difference in the parameters between ureteropelvic and bladder TCCs. On the other hand, invasive TCCs (pT2 and higher), the C-AgNOR and P-AgNOR were significantly higher in ureteropelvic than in bladder TCC (p < 0.05), while no significant difference in 2cDI, 5cFR and MNA was noted. These findings suggest that: (i) as a whole, the difference in malignant potential between ureteropelvic and bladder TCCs appears to be less significant, and (ii) factors other than the malignant potential of a tumor might contribute to the unfavorable clinical outcome in patients with ureteropelvic TCC.

The value of ultrastructural evaluation in the diagnosis of renal tumors: a general overview

The understanding of renal neoplasia has advanced significantly in the last 20 years. New challenges have arisen as a consequence of prolonged dialysis and renal transplantation becoming the therapeutic modes to deal with chronic renal disease. Immunosuppression resulting from primary disease processes or as a result of clinical intervention has resulted in an increase in neoplasia in general and changes in manifestations and clinical behavior of tumors. Special techniques such as immunocytochemistry and electron microscopy have provided information that has resulted in refinement of diagnostic and conceptual issues. The variable gross and histological manifestation of many of the renal neoplasms can be explained at least in part by reflecting on the new fundamental knowledge that has been acquired regarding renal developmental biology. A more aggressive approach from a therapeutic point of view placing emphasis on specific treatment protocols for the various nosologic entities further emphasizes the need to understand the advances that have taken place in the field. This article provides an overview of the subject, with emphasis on an overall conceptual understanding, to serve as a practical framework. The articles that follow address the specific current role of ultrastructure in the diagnosis and understanding of renal neoplasms.

The role of ultrastructural pathology in the diagnosis of epithelial and unusual renal tumors

The electron microscopic and immunohistochemical features of epithelial and unusual renal tumors are reviewed. Ultrastructural and immunohistochemical features of diagnostic value are highlighted. An attempt is made to address histogenesis/differentiation issues that would help in understanding morphologic findings, with an emphasis placed on the role that ultrastructural evaluation has played in demonstrating these.

Renal cell carcinoma with unusual differentiation

A 4-cm tumor in the kidney of a 67-year-old male was focally a classical renal cell carcinoma with a papillary architecture and clear cells, but most of the tumor had an unusual pattern composed of paired sheets of cuboidal to flattened cells reminiscent of the loop of Henle.

Renal cell carcinoma: histological findings in peritumoral tissue after organ-preserving surgery

OBJECTIVE AND METHOD

This study assessed the involvement of peritumoral renal cell carcinoma tissue and evaluated the efficacy of partial resection versus enucleation by an anatomopathological investigation into the resection margins in 28 cases of partial nephrectomy.

RESULTS

Histological findings showed no peritumoral infiltration in 91.6% of elective partial resections (24 patients) and resection margin involvement in 75% of necessary partial resections (4 patients).

CONCLUSION

Although the debate between organ-preserving and radical surgery remains open, the conservative approach can undoubtedly be recommended in selected patients.