Transmission Electron Microscopy: A Surgical Pathology Tool for Neuroblastoma.

Pediatric small round blue cell tumors (PSRBCT) are an intriguing and challenging collection of neoplasms. Light microscopy of small round blue cell tumors identifies small round cells. They harbor a generally hyperchromatic nucleus and relatively scanty basophilic cytoplasm. Pediatric small round blue cell tumors include several entities. Usually, they incorporate Wilms tumor, neuroblastoma, rhabdomyosarcoma, Ewing sarcoma, retinoblastoma, lymphoma, and small cell osteosarcoma, among others. Even using immunohistochemistry, the differential diagnosis of these neoplasms may be controversial at light microscopy. A faint staining or an ambiguous background can deter pathologists from making the proper diagnostic decision. In addition, molecular biology may provide an overwhelming amount of data challenging to distinguish them, and some translocations may be seen in more than one category. Thus, transmission electron microscopy (TEM) can be extremely valuable. Here we emphasize the modern protocol for TEM data of the neuroblastoma. Tumor cells with tangles of cytoplasmic processes containing neurosecretory granules can diagnose neuroblastoma.

Impact of Wilms' tumor 1 expression on outcome of patients undergoing allogeneic stem cell transplantation for AML.

The monitoring of the minimal residual disease by Wilms' tumor 1 expression (MRDWT1) is a standardized test, which can be used in over 80% of patients with AML. To investigate the prognostic value of MRDWT1 in patients undergoing allogeneic stem cell transplantation (allo-SCT) for AML, MRDWT1 was monitored 3 months after transplantation in 139 patients. MRDWT1 positivity did not lead to any therapeutic intervention. Median follow-up was 39.3 (6.4-99.8) months. Patients with positive MRDWT1 at 3 months experienced more often post-transplant relapse (27/30, 90%) than those with negative MRDWT1 (16/109, 14.7%) (P<0.0001). Similarly, a shorter 3-year event-free survival (EFS) was observed in MRDWT1-positive patients (10% vs 72.3% in MRDWT1-negative patients, P<0.0001). The correlation between relapse and MRDWT1 was stronger in blood than in bone marrow samples. Multivariate analysis confirmed the detrimental role of 3-month positive MRDWT1 for relapse (hazard ratio (HR): 15.42; 95% confidence interval (CI): 7.53-31.59; P<0.0001) and EFS (HR: 10.71; 95% CI: 5.41-21.21; P<0.0001). Interestingly, 3-month chimerism was less predictive of relapse than positive MRDWT1. In conclusion, our results demonstrate the usefulness of peripheral blood MRDWT1 monitoring in identifying very high-risk patients, who could benefit from an early preemptive treatment, and those who do not need such an intervention.

Diagnostic utility of cyclin D1 in the diagnosis of small round blue cell tumors in children and adolescents.

Small round blue cell tumors (SRBCTs) of children and adolescents are often diagnostically challenging lesions. With the increasing diagnostic approach based on small biopsies, there is the need of specific immunomarkers that can help in the differential diagnosis among the different tumor histotypes to assure the patient a correct diagnosis for proper treatment. Based on our recent studies showing cyclin D1 overexpression in both Ewing sarcoma/primitive peripheral neuroectodermal tumor (EWS/pPNET) and peripheral neuroblastic tumors (neuroblastoma and ganglioneuroblastoma), we immunohistochemically assessed cyclin D1 immunoreactivity in 128 cases of SRBCTs in children and adolescents to establish its potential utility in the differential diagnosis. All cases of EWS/pPNET and the undifferentiated/poorly differentiated neuroblastomatous component of all peripheral neuroblastic tumors exhibited strong and diffuse nuclear staining (>50% of neoplastic cells) for cyclin D1. In contrast, this marker was absent from rhabdomyosarcoma (regardless of subtype) and lymphoblastic lymphoma (either B- or T-cell precursors), whereas it was only focally detected (<5% of neoplastic cells) in some cases of Wilms tumor (blastemal component) and desmoplastic small round cell tumor. Our findings suggest that cyclin D1 can be exploitable as a diagnostic adjunct to conventional markers in confirming the diagnosis of EWS/pPNET or neuroblastoma/ganglioneuroblastoma. Its use in routine practice may also be helpful for those cases of SRBCT with undifferentiated morphology that are difficult to diagnose after application of the conventional markers.

Wilms tumor 1 mutations in the pathogenesis of acute myeloid leukemia.

Wilms tumor 1 (WT1) has long been implicated in acute myeloid leukemia. It has been described to be both overexpressed and mutated in different forms of acute myeloid leukemia, and overexpression has been reported to play a prognostic role in this disease. However, the precise mechanism through which WT1 may play a role in leukemogenesis has remained elusive. In recent years, new evidence has emerged that points towards a novel role of WT1 mutations in the deregulation of epigenetic programs in leukemic cells through its interaction with TET proteins. Herein we review the current status of the field and its therapeutic and prognostic implications in acute myeloid leukemia.

Diagnostic pitfalls of differentiating desmoplastic small round cell tumor (DSRCT) from Wilms tumor (WT): overlapping morphologic and immunohistochemical features.

Desmoplastic small round cell tumor (DSRCT) and blastemal-predominant Wilms tumor (WT) share overlapping histologic features, yet accurate distinction is critical because of differing prognosis and treatment. We encountered a neck mass in a young adult with a concomitant abdominal mass. The neck mass was initially concerning for DSRCT on the basis of the poorly differentiated morphology, desmoplastic stroma, and immunoreactivity for desmin and cytokeratin. However, focal triphasic elements and glomeruloid bodies were identified on deeper sections, WT1 immunoreactivity was seen with antibodies to both the amino-terminus and carboxy-terminus, and EWSR1-WT1 rearrangement studies were negative, supporting the ultimate diagnosis of WT. On the basis of the overlapping histologic features of DSRCT and blastemal-predominant WT, we undertook a comparison study of desmin and cytokeratin reactivity patterns. We found that, whereas desmin reactivity was more frequent in DSRCT (11 of 12) than in WT blastema (11 of 22, P=0.024), dot-like perinuclear reactivity was seen with equal frequency in desmin-reactive DSRCT (10 of 11) and WT blastema (10 of 11), illustrating an important diagnostic pitfall. Moreover, we demonstrate coexpression of desmin and cytokeratin in both DSRCT (9 of 12) and WT blastema (11 of 22). Importantly, although dot-like desmin reactivity and coexpression of desmin and cytokeratin are historically associated with DSRCT, we demonstrate that these features can be seen in either DSRCT or blastemal-predominant WT. In these challenging cases, detection of an EWSR1-WT1 rearrangement and selective WT1 carboxy-terminus immunoreactivity (characteristic of DSRCT) or dual immunoreactivity for the WT1 amino-terminus and carboxy-terminus (characteristic of WT) remain the most discriminating diagnostic tools.

Association of E2F3 expression with clinicopathological features of Wilms' tumors.

PURPOSE: The transcription factor E2F3 plays an important role in controlling cell cycle progression and proliferation, and is overexpressed in various human cancers. The present study was undertaken to examine the expression of E2F3 and investigate its relevance in clinical and pathological features of pediatric Wilms' tumors. METHODS: Twenty-six Wilms' tumor samples collected at the First Affiliated Hospital of Harbin Medical University underwent immunohistochemical staining for E2F3 protein expression by measuring the percentage of E2F3-positive cells and integrated optical density (IOD), and quantitative real-time polymerase chain reaction (qRT-PCR) for E2F3 mRNA expression. RESULTS: The expression of E2F3 protein and mRNA was detectable in all the Wilms' tumor samples with big variations (The average percentage of positive cells was 30.2%±23.5%, range 0.3%-75.6%; average IOD was 6.61×10(4)±3.92×10(4), range 2.32×10(4)-13.84×10(4); average relative mRNA unit was 0.54±0.38, range 0.03-1.31), but not in fetal kidney tissues. Wilms' tumors with aggressive features, such as higher stage, unfavorable histology and higher risk level, expressed higher levels of E2F3 protein and mRNA. CONCLUSIONS: The preliminary data indicate that E2F3 is frequently expressed in pediatric Wilms' tumors examined in the present study. E2F3 expression may be associated with Wilms' tumors, particularly those that have more aggressive features. However, further studies are needed to validate these pilot observations and to clarify the functional and mechanistic significance of this association.

Differential expression of STAT1 and IFN-γ in primary and invasive or metastatic wilms tumors.

BACKGROUND AND OBJECTIVES: IFN/STAT1 signaling has been found to be not only associated with an aggressive tumor phenotype but also activated and functional during metanephric development. This study was undertaken to evaluate STAT1 and IFN-γ expression and its relation to histopathological features of primary and invasive/metastatic Wilms tumors. METHODS: Immunohistochemistry was used to determine the expression and cellular distribution of STAT1 and IFN-γ in 18 pairs of primary and corresponding invasive/metastatic Wilms tumors and 40 primary tumors without invasion or metastasis. RESULTS: Positive rate of STAT1/IFN-γ expression was 66.7%/61.1% and 72.2%/77.8% in 18 pairs of primary and associated invasive/metastatic Wilms tumor tissues, while 35.0%/27.5% in 40 primary tumors without invasion or metastasis. The expression of STAT1 and IFN-γ was significantly associated with invasion/metastasis (P = 0.025; P = 0.015). There was a positive correlation between STAT1 and IFN-γ expression in all Wilms tumor tissues (χ(2) = 23.408, P = 0.05, r = 0.555). The expression of STAT1 and IFN-γ between primary and matched invasive/metastatic tissues was concordance, respectively (P = 0.710 and P = 0.375). CONCLUSIONS: These results suggest that IFN-γ/STAT1 signaling might have clinical potential as a promising predictor to identify individuals with poor prognostic potential and as a possible novel target molecule of therapy for Wilms tumor.

p53 Immunohistochemistry expression in Wilms tumor: a prognostic tool in the detection of tumor aggressiveness.

PURPOSE: We studied whether immunohistochemical expression of p53 in Wilms tumors correlates with tumor aggressiveness. We also examined whether preoperative chemotherapy results in any alteration of p53 expression. MATERIALS AND METHODS: A total of 18 patients underwent preoperative chemotherapy and 30 underwent immediate surgery for Wilms tumor. All children were younger than 10 years and had histologically confirmed disease. Patients with a bilateral tumor or a syndrome related to Wilms tumor were excluded. All pathology slides were uniformly stained for p53 protein, and p53 staining density and intensity were scored. The p53 scoring was then compared to the clinical behavior of the Wilms tumor, ie unfavorable tumor staging, and survival and recurrence rates. RESULTS: In the direct surgery and the preoperatively treated groups p53 positivity correlated with unfavorable Wilms tumor staging (p = 0.007). In addition, a positive p53 correlation predicted poorer survival (p = 0.017). Interestingly patients who underwent preoperative chemotherapy had an increased intensity of p53 staining compared to the direct surgery group (p <0.001). CONCLUSIONS: This study provides preliminary evidence that a higher score for immunohistochemical p53 expression correlates with unfavorable Wilms tumor staging and predicts poorer survival. This test could become a useful addition to the current histopathological analysis of Wilms tumor.

B7-h1 as a biomarker for therapy failure in patients with favorable histology Wilms tumor.

PURPOSE: A minority of children with Wilms tumor will experience tumor recurrence. In a previous pilot study we found an association between expression of an immune costimulatory molecule, B7-H1, and tumor recurrence in favorable histology Wilms tumor. We sought to verify the prognostic value of B7-H1 as a biomarker in favorable histology Wilms tumor. MATERIALS AND METHODS: We performed a nested case-control study of tumors from the Fifth National Wilms Tumor Study. We randomly selected 44 children unsuccessfully treated (cases) and 49 who were successfully treated for favorable histology Wilms tumor (controls). Cases and controls were matched based on tumor stage, and the analysis was restricted to children who underwent initial resection. We excluded patients with stage IV or V disease and those treated with chemotherapy or radiation. Tumor specimens were stained for B7-H1 expression. RESULTS: Of the 93 total samples analyzed 60 (65%) demonstrated B7-H1 staining, with staining diffusely present in 13 (22%) and blastema predominant in 34 (57%). B7-H1 expression was associated with failure of initial therapy (p = 0.006). Patients with tumors showing less than 20% B7-H1 positive cells were at lower risk for treatment failure, while those with tumors exhibiting greater than 60% B7-H1 positive cells were at greater risk for treatment failure. This association appeared to be independent of tumor stage. CONCLUSIONS: B7-H1 expression by favorable histology Wilms tumor is associated with an increased risk of failure of initial therapy.

Prognostic value of survivin expression in Wilms tumor.

PURPOSE: To determine survivin expression patterns in Wilms tumor (WT) and compare it with the expression in normal renal tissue. Also, to analyse cytoplasmic and nuclear survivin expression in relation to histological type, prognostic group and tumor stage. METHODS: Immunohistochemical expression of survivin was analysed in 59 cases of primary WT and in 10 normal kidney specimens, taken from the same patients, but distant from the tumor. RESULTS: 51 out of 59 cases of WT (86.44%) showed decreased cytoplasmic survivin expression and 4 out of 59 cases of WT (6.78%) showed nuclear overexpression of survivin. There was statistically significant difference in the frequency of decreased cytoplasmic expression of survivin in individual components of WT (p=0.005). Decreased cytoplasmic expression of survivin in epithelial, blastemal and stromal component was found significantly more often in low stage WT compared to high stage WT (Fisher exact test, p=0.0002, p=0.002, p=0.002, respectively). There was no statistically significant difference in the frequency of survivin nuclear overexpression between different stages of WT (Fisher exact test, p=0.564), histological types (Fisher exact test, p=0.915), or between different prognostic groups (Fisher exact test, p=1). CONCLUSION: Decreased survivin cytoplasmic expression or nuclear overexpression may be related to favorable prognosis of WT.

PAX2 expression in Wilms tumors and other childhood neoplasms.

PAX2 plays an important role in kidney development; although small studies have demonstrated PAX2 expression in Wilms tumors (WT), comprehensive studies on formalin-fixed tissue are lacking. Thus, we systematically evaluated PAX2 immunohistochemical staining in a retrospective study of pediatric WT, as compared with other pediatric tumors. We stained formalin-fixed, paraffin-embedded sections from 39 WT, 6 nephrogenic rests, 8 non-Wilms renal tumors, and 43 nonrenal pediatric small round cell tumors with 2 different PAX2 polyclonal antibodies. PAX2 demonstrated strong, diffuse staining of epithelial and blastema components of WT (97% of cases). PAX2 stained WT stroma in fewer cases (23%), but 80% of anaplastic foci were positive. Nephrogenic rests, 1 case of metanephric adenoma, and 1 pediatric renal cell carcinoma were also PAX2 positive; other pediatric renal tumors were negative. Neuroblastoma, primitive neuroectodermal tumor/Ewings, and T-cell acute lymphoblastic lymphoma (ALL) were PAX2 negative. However, PAX2 weakly stained some cases of B-cell ALL rhabdomyosarcoma (RMS) was also stained, especially alveolar RMS (83%), with less staining of embryonal RMS (13%). One of the antibodies also stained maturing myoid cytoplasm of WT and RMS. This study shows that PAX2 is a sensitive marker of WT (sensitivity 97%), but PAX2 shows weak-to-moderate-intensity nuclear staining of RMS and B-cell ALL, somewhat limiting its utility. However, PAX2 may be a helpful marker in certain diagnostic situations. We speculate that RMS and B-cell ALL staining could be due to antibody cross-reactivity with PAX family members with known expression in RMS and B-cell ALL.

Cytoplasmic p63 immunohistochemistry is a useful marker for muscle differentiation: an immunohistochemical and immunoelectron microscopic study.

TP63, a member of the TP53 gene family, is a nuclear marker of myoepithelial cells. Antibody against p63 is frequently used to aid in the diagnosis of prostate carcinoma, as well as in the identification of myoepithelial cells in other tissues including the breast. p63 is also a marker for squamous cell carcinoma. Recently, it was found that all p53 family members are involved in regulating the process of muscle differentiation through the retinoblastoma (RB) protein. Ablation of these p53 family functions blocks the differentiation program and promotes malignant transformation by enabling cooperating oncogenes to transform myoblasts. We therefore studied p63 expression in a number of neoplasms with myogenic differentiation. Immunohistochemical staining for p63 was performed on paraffin sections from 38 rhabdomyosarcomas, five leiomyomas, five leiomyosarcomas, five rhabdomyomas, five rhabdomyomatous Wilms tumors, three normal cardiac muscles, one medullomyoblastoma, one pleuropulmonary blastoma with rhabdomyomatous differentiation, and one teratoma with prominent rhabdomyoblasts. Each case was also stained with desmin. Unlike the nuclear staining scored in myoepithelial cells, only cytoplasmic staining for p63 was considered positive. Of 38 cases of rhabdomyosarcoma, 36 showed cytoplasmic p63 staining; 24 of these showed highlighting of cross-striations superior to that of desmin. In addition, 5/5 rhabdomyomas, 5/5 rhabdomyomatous Wilms tumors, 1/1 pleuropulmonary blastoma with rhabdomyomatous differentiation, 1/1 teratoma with atypical rhabdoblasts, and 1/1 medullomyoblastoma exhibited cytoplasmic p63 staining. Normal cardiac muscle samples (3/3) also demonstrated positive cytoplasmic staining and distinct cross-striations. Smooth muscle tumors exhibited only very focal and faint cytoplasmic staining in 5/5 leiomyomas and 4/5 leiomyosarcomas. Immunoelectron microscopic study of skeletal muscle showed p63 localization to the Z bands of sarcomeres. We conclude that p63 immunostain is a sensitive marker for skeletal muscle differentiation and highlights the cross-striations of strap cells with exceptional definition.

Analysis of multiple growth regulatory proteins using dissociable staining antibody arrays on solid tumor biopsy specimens.

Growth of tumor cells is often a function of deregulated growth factor receptors and their corresponding intracellular signalling molecules. The dissociable antibody staining arrays have the versatility to rapidly identify the expression, activation, and localization of such molecules and pathways in biopsy specimens. This report describes a protocol to quantify the activity of a panel of signalling molecules in Wilms tumor biopsy specimens and surrounding nonmalignant renal cells. We propose that this technique can be used to rapidly identify multiple markers and may aid in the study of aberrant growth regulatory mechanisms and potential targets for therapeutics from pathologic specimens.

Increased tissue factor expression and poor nephroblastoma prognosis.

PURPOSE: There is potential interaction between malignant cell growth and the coagulation pathway. Recent studies suggest that tissue factor, a primary initiator of the extrinsic coagulation pathway, is expressed in various solid tumors in association with increased angiogenesis. To our knowledge we report for the first time the detection of tissue factor expression by immunohistochemistry in Wilms tumors and its correlation with clinical outcomes. MATERIAL AND METHODS: Tissue factor expression detected by immunohistochemistry was assessed in 41 formalin fixed, paraffin embedded Wilms tumor cases treated at university hospitals. We correlated findings with tumor recurrence and cancer specific survival. RESULTS: Positive immunohistochemistry detection of tissue factor was observed in 88.3% of the tumors analyzed. Tissue factor on immunohistochemistry was associated with tumor recurrence and survival (p = 0.01 and 0.02, respectively). Increased immunohistochemical detection of tissue factor was the most important risk factor for recurrence and mortality in our population on bivariate and multivariate analysis. CONCLUSIONS: Tissue factor is a promising research subject as a prognostic factor for Wilms tumor. More studies are needed to clarify the mechanisms by which tissue factor affects cancer progression and outcome, and its potential role as a therapeutic target.

PAX immunoreactivity identifies alveolar rhabdomyosarcoma.

PAX5 is a member of the paired box transcription factors involved in development and its expression has been well characterized among hematopoietic malignancies of B-cell lineage. Its expression has also been reported in a subset of neuroendocrine carcinomas, urothelial tumors, Merkel cell carcinoma, glioblastoma, and neuroblastoma cell lines. As such, we sought to assess it as a diagnostic marker in the evaluation of pediatric small round blue cell tumors. Tumors selected for evaluation included embryonal rhabdomyosarcoma (55 cases), alveolar rhabdomyosarcoma (ARMS) (51 cases), neuroblastoma (22 cases), Wilms tumor (18 cases), Ewing Family of Tumors (11 cases), lymphoblastic lymphoma (8 cases), hepatoblastoma (6 cases), and granulocytic sarcoma (3 cases) as either cores in a tissue microarray or whole mount sections. All cases were immunostained using an antibody directed toward PAX5 and immunoreactivity was scored semiquantitatively according to percentage of nuclear staining. As expected, all B-cell lymphoblastic lymphomas were strongly immunoreactive against PAX5. Additionally, all Wilms tumors showed staining of variable intensity, most intensely in the epithelial component. Of the rhabdomyosarcoma cases, 34 of 51 (67%) ARMS were immunoreactive whereas none of the 55 embryonal rhabdomyosarcoma cases stained. No other tumor type on the array was immunoreactive toward PAX5. Genetic information was available on 7 ARMS, 5 of which had characteristic translocations involving PAX genes, either t(2:13) or t(1;13). Of the translocation-positive cases, all showed nuclear reactivity toward PAX5, and both the translocation-negative cases did not. Possible explanations of PAX5 staining include aberrant expression of the PAX5 transcription factor, PAX5 expression in normal tissue at the time the tumors most closely recapitulates in development or crossreactivity with another member of the PAX family. PAX3 and PAX7 fusion genes characterize the majority of ARMS making crossreactivity with these proteins an attractive theory, and suggest that PAX5 immunoreactivity may be specific for translocation-positive ARMS. Further study in a larger series of rhabdomyosarcomas is warranted to assess the sensitivity and specificity of PAX5 immunoreactivity for the ARMS variant.

Adult extrarenal Wilms tumor of the uterus with teratoid features.

The present article reports for the first time a case of an extrarenal teratoid Wilms tumor in the uterus of a 62-year-old woman. It had triphasic histology with epithelial areas composed of metanephric tubules harboring glomerular structures, adamantine patterns, neural type rosettes, blastema, and a primitive, myxoid type stroma. Abundant heterologous elements such as cartilage, striated muscle, squamous epithelium, and an alpha fetoprotein and TTF1-positive early endodermal epithelium were also present. Immunohistochemistry in Wilms tumor areas showed positivity for markers also indicative of peripheral primitive neuroectodermal tumors such as neuron-specific enolase, CD99, and CD56. However, nuclear positivity for Wilms tumor antigen together with the presence of glomeruli and the absence of endometrioid tumor areas and the organoid arrangement of tissues excluded peripheral primitive neuroectodermal tumors, carcinosarcoma, and teratoma, respectively. Although the diagnosis of female genital tract Wilms tumors is difficult in cases where glomerular structures are lacking, it should be considered because these neoplasms have a better therapeutic response than peripheral primitive neuroectodermal tumors and carcinosarcoma.

S100 protein expression distinguishes metanephric adenomas from other renal neoplasms.

Metanephric adenoma is a benign renal neoplasm with morphologic features similar to those of malignant renal neoplasms, such as papillary renal cell carcinoma (RCC) and Wilms' tumor. Different methods have been used to distinguish between metanephric adenoma and papillary RCC and Wilms' tumor. However, some techniques are not always available, such as certain immunohistochemical stains, cytogenetics, molecular genetics, and electron microscopy. In the current study, we compared the expression of S100 protein in 15 cases of metanephric adenoma, 10 cases of Wilms' tumor, and 13 cases of papillary RCC. Our results revealed strong expression of S100 proteins in all cases of metanephric adenoma, weak expression in two cases of Wilms' tumor, and no expression in any of the cases of papillary RCC. These findings indicate that S100 could be a useful and accessible tool for the diagnosis of metanephric adenoma.

Role of DNA content analysis and immunohistochemistry in the evaluation of the risk of unfavourable outcome in Wilms' tumours.

BACKGROUND: Wilms' tumour (WT) is the most common solid tumour affecting young children. Its histological diversity leads to difficulties in predicting the outcome. MATERIALS AND METHODS: Image analysis cytometry and immunohistochemistry with a selected panel of antibodies were performed in 23 cases of WT considered of intermediate risk according to the revised International Society of Pediatric Oncology (SIOP) working classification of renal tumours of childhood. In this series, a tumour was considered aggressive according to its propensity for metastases or its recurrence. RESULTS: Out of the 14 non-aggressive WT, 4 were found to be diploid and 10 were aneuploid including 6 that were heterogeneous for DNA-ploidy. All the tumours presented a low proliferative index and were negative for p53 and p57(kip2) immunostaining. Out of the 9 aggressive tumours, all were aneuploid and 4 were found to be heterogeneous for DNA-ploidy. They all presented a high degree of cell proliferation and 7 were positive for p53 immunostaining. Only two were positive for the p57(kip2) marker. The only fatal case revealed an aneuploid-homogeneous DNA-ploidy analysis, was p53 and p57(kip2) positive and presented a high cell proliferation index. CONCLUSION: A significant correlation between the presence of focal DNA-aneuploidy in Wilms' tumours and adverse prognosis is not established, but some immunohistochemical markers may be useful for the clinical evaluation of these tumours and to help in predicting the risk of an unfavourable outcome.