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PubMed1998

Rhabdomyosarcoma mimicking acute leukemia in an adult: report of a case with histologic, flow cytometric, cytogenetic, immunohistochemical, and ultrastructural studies.

A case of a 25-year-old man who presented with low back, knee, and hip pain with bruising, leukocytosis, and thrombocytopenia is reported. Histopathologic and flow cytometric studies revealed a malignant neoplasm, which was thought to be consistent with an unusual type of acute leukemia. Subsequent immunohistochemical studies revealed diffuse bone marrow involvement by rhabdomyosarcoma, demonstrated by positivity for desmin and muscle-specific actin. In addition, the diagnosis of metastatic rhabdomyosarcoma was confirmed with cytogenetic and ultrastructural studies. The incidence of rhabdomyosarcoma, a disease usually seen in childhood, presenting with extensive bone marrow involvement and mimicking acute leukemia in an adult is extremely rare. This case highlights the need to consider rhabdomyosarcoma in the differential diagnosis in patients who present with a leukemic picture and atypical blasts that lack the usual hematopoietic markers.

Actins↗
PubMed1998

Up-regulation of MET but not neural cell adhesion molecule expression by the PAX3-FKHR fusion protein in alveolar rhabdomyosarcoma.

The 2;13 chromosomal translocation in alveolar rhabdomyosarcoma generates the chimeric protein PAX3-FKHR, which is a powerful transcriptional activator. We hypothesize that PAX3-FKHR regulates downstream effector genes involved in rhabdomyosarcoma tumorigenesis. We evaluated alterations in expression of MET and neural cell adhesion molecule that were proposed previously as downstream targets of wild-type PAX3. We used a myogenic tumor cell culture system and rhabdomyosarcoma tumor specimens to assess candidate gene expression in relationship to various PAX3-FKHR expression levels. We demonstrate that the expression of MET, but not neural cell adhesion molecule, correlates significantly with PAX3-FKHR expression. These findings indicate that MET, which encodes a receptor involved in growth and motility signaling, is a downstream target of PAX3-FKHR in alveolar rhabdomyosarcoma.

Cells, Cultured↗
PubMed1976

[Embryonal rhabdomyosarcoma of the urinary bladder in childhood. Report of five own cases].

Malignant lesions of the bladder in infancy and early childhood arise from mesenchymal tissue. Among the mesenchymal tumors embryonal rhabdomyosarcoma is more common in young children than in adults. The gross appearance of rhabdomyosarcoma of the bladder is typically that of polypoid grapelike clusters of tissue, termed "sarcoma botryoides". Histologically, the lesion is consistent with embryonal rhabdomyosarcoma. The growths originate in the submucosal layer of the trigone and the internal urethral orifice. Rhabdomyosarcoma (RMS) of the bladder in children tends to remain within the disease. Deep extension and metastasis to regional lymph nodes and to distant sites is a relatively late occurrence. The symptoms are characteristically those of obstruction and strangury. Hematuris is uncommon. The intravenous urogram shows characteristic lobulated filling defects. Treatment of choice is almost always total cystectomy. Suprapubic cystotomy must be prohibited both as a method of drainage and as an approach for biopsy since tumors ulcerating through the abdominal wall after cystotomy and local excision have been observed. With concomitant administration of radiation therapy in selected cases and the combination of surgery with multiple drug chemotherapy, promising results have been obtained in the therapy of embryonal RMS of the bladder in children.

Age Factors↗
PubMed1994

Primary chemotherapy for children with rhabdomyosarcoma of the 'special pelvic' sites: is preservation of the bladder possible?

Twenty-one children with rhabdomyosarcoma involving the "special pelvic" sites, defined as such occurring in the bladder, prostate, vagina and uterus, were treated with primary surgery between 1969 and 1977, and with primary chemotherapy beginning in 1978. Among 11 patients in the latter group who were placed in Clinical Group III (according to the classification of the US Intergroup Rhabdomyosarcoma Study (IRS), six showed partial response (PR) and underwent tumorectomy by radical surgery an average of 6 months after the start of treatment, and three showed complete response (CR) and were treated with further chemotherapy in the hope that cystectomy could be avoided. However, in the latter group, the tumor recurred (39 months, 35 months, and 27 months later), and all eventually underwent total cystectomy. Seven of the nine long-term survivors underwent total cystectomy and have premanent urinary-cutaneous stomas. Two had tumor-free bladders, but function was impaired in one because of the effect of irradiation. Normal function was preserved in only one patient in the series, whose tumor was located at the dome of the bladder. To preserve bladder function in children with rhabdomyosarcoma in these sites, more effective forms of chemotherapy will be required.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

Rhabdomyosarcoma of the nose and paranasal sinuses in adults and children.

OBJECTIVE: To determine the biologic behavior, risk factors for recurrence, and influence of multimodality therapy on outcome for children and adults with rhabdomyosarcoma of the nose and paranasal sinuses. DESIGN: Retrospective review of medical records. PATIENTS: During a 36-year period 37 patients (median age, 23.0 years) with histologically confirmed rhabdomyosarcoma of the nose and paranasal sinuses were treated for cure. Median follow-up was 28 months (range, 1 to 260 months). Histologic subtypes included embryonal, 16; alveolar, 15; mixed, 1; and unclassified, 5. Cervical metastases were present in 38%. Patients were treated with surgery, 4; radiotherapy, 3; chemotherapy, 3; surgery and radiotherapy, 1; surgery and chemotherapy, 1; chemotherapy and radiotherapy, 24; and chemotherapy, radiotherapy, and surgery, 1. RESULTS: The overall 5-year survival was 44%. For patients treated with chemotherapy and radiotherapy or chemotherapy, radiotherapy, and surgery, the 5-year survival was 60%, compared with 19% for patients treated with the other forms of therapy. Factors associated with poorer survival were adult onset of disease, alveolar histology, and treatment with systemic chemotherapy for less than 1 year. Patients receiving chemotherapy for greater than 1 year had a 5-year survival of 82%, compared with 71% for those with less than 1 year of treatment. Improved survival was associated with a lower incidence of distant metastasis. CONCLUSIONS: A combination of chemotherapy and radiotherapy may provide the best means of obtaining local-regional control for rhabdomyosarcoma arising in the nose and paranasal sinuses. The risk of regional disease is high, requiring comprehensive radiotherapy to the neck in addition to the primary site. Surgical resection should be reserved for patients with residual disease after chemotherapy and radiotherapy. Administration of chemotherapy for more than 1 year is associated with improved survival because of a decreased incidence of metastatic disease.

Adolescent↗
PubMed1994

Histopathological features and grading in rhabdomyosarcomas of childhood.

Rhabdomyosarcoma represents a large group of soft tissue sarcomas displaying heterogeneous histopathological features. In addition to their histopathological classification, the variable expression of a number of histopathological features may contribute to the heterogeneity and may be related to prognosis. Tissue sections of 113 well-documented, protocol-treated patients with long term follow-up (mean 6 years) were analysed by a panel of four paediatric pathologists. The following features were assessed: presence of rhabdomyoblasts, degree of maturation of rhabdomyoblasts, heterogeneous maturation patterns, mitotic activity, tumour necrosis, myxoid component, and septa. A scoring system was allocated to each index. High degree of maturation (amount of cytoplasm greater than surface area of the nucleus), absence of tumour necrosis (< 10% of tumour surface), and absence of septa (< 10% of tumour surface) significantly correlated with a favourable clinical course. Reproducibility in the assessment of these three features was good: mean kappa varying from 0.53 to 0.64. A rhabdomyosarcoma score function for survival was defined by: (-0.27 x degree of maturation score) + (0.007 x percentage septated area) + (0.031 x percentage tumour necrosis). Based on the score a two-grade system was elaborated, i.e. grade I (score < -0.20) v. grade II (score > or = -0.20). Rhabdomyosarcoma grade appeared to be the best factor in predicting patients survival: 69% long-term survival in patients with grade I v. 33% in patients with grade II (P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Cellular expression of adhesion factors in childhood rhabdomyosarcoma.

Tumor invasion and metastasis are believed to involve the adhesive interaction of tumor cells with extracellular matrix (ECM). This study reports the expression of laminin, fibronectin, thrombospondin, tenascin, and CD44 in rhabdomyosarcoma cells taken from tumors derived from 12 pediatric patients. Twelve paraffin-embedded rhabdomyosarcomas consisting of five alveolar, six embryonal, and one botryoid subtype were examined. All tumors demonstrated positive staining for tenascin and thrombospondin, 10 were positive for fibronectin, 5 positive for laminin, and 4 positive for CD44. Both specimens without cellular staining for fibronectin were of embryonal subtype and no alveolar rhabdomyosarcomas were positive for CD44. No association of the expression of the studied ECM proteins and receptor with the presence of metastatic disease at clinical presentation or with the level of tumor differentiation was found.

Adolescent↗
PubMed1999

Expression of neural cell adhesion molecules and neurofilament protein isoforms in Ewing's sarcoma of bone and soft tissue sarcomas other than rhabdomyosarcoma.

In a previous study, it was shown that rhabdomyosarcomas widely express "neural" markers, such as neural cell adhesion molecules (N-CAM) and neurofilament protein isoforms. In the current study, a series of Ewing's sarcomas of bone and soft tissue sarcomas other than rhabdomyosarcoma was probed for the same antigens. It was found that N-CAM was widely expressed in the various sarcoma types, except Ewing's sarcomas, though less than in rhabdomyosarcomas. Similar to rhabdomyosarcomas, neurofilament isoforms were found throughout all sarcoma types but were largely restricted to those expressed early in neurogenesis, that is, poorly phosphorylated medium-weight isoforms. Neurofilament expression was most extensive in Ewing's sarcomas. It was concluded that the expression of "neural" markers (N-CAM, neurofilaments) is widespread in sarcomas and does not signify a neural tumor. The absence of N-CAM expression in Ewing's sarcoma may be helpful in its distinction from other sarcomas.

Adolescent↗
PubMed1997

Rhabdomyosarcoma of Parameningeal Sites.

Rhabdomyosarcoma arising in the skull base has a feature of its natural history that is unique in oncology: by virtue of parameningeal location and invasive behavior, it can extend intracranially and produce neoplastic meningitis. The four anatomic sites with this potential are the nasopharynx/nasal cavity, the middle ear, the paranasal sinuses, and the infratemporal fossa/pterygopalatine space. Patients with these primary sites comprise 41% of patients with head and neck sites and 15% of all patients with rhabdomyosarcoma. Most are under 10 years old at diagnosis (72%) and are Intergroup Rhabdomyosarcoma Study (IRS) Clinical Group III (76%). IRS protocols over the last 20 years have lead to a gradual improvement in outcome while refining radiation treatment parameters to allow for restricted indications for (and then the elimination of) whole cranial radiotherapy ports. The current guidelines (Group III) are for a dosage of 1.8 Gy/d up to a total of 50.4 Gy using 2-cm margins around the gross tumor volume at diagnosis. The timing of radiotherapy in relation to combination chemotherapy is based on assessment of three risk factors that predict tumor access to the cranial subarachnoid space: skull base erosion, cranial nerve palsy, and intracranial extension. Patients with one or more factors begin radiotherapy concurrently with chemotherapy. The remaining one third of patients begin radiotherapy after induction chemotherapy (week 9). The 5-year failure-free survival rate for patients with Group III parameningeal rhabdomyosarcoma on IRS-III was 71%. In the absence of the three risk factors, 5-year survival was 97%. The local failure rate was 15%. Among patients who achieved a compete or partial response (IRS-III), 5% had contiguous ((nonhematogenous) central nervous system failure. Late effects of radiotherapy in these young patients are protean and include growth inhibition, cataracts, impaired dentition and hearing, and facial bone asymmetry. The promise of improvement of the therapeutic ratio may be realized from treatment refinements, which include chemotherapy response-based portal reduction, hyperfactionation, and conformal radiation therapy.

Journal Article↗
PubMed2006

Postauricular congenital alveolar rhabdomyosarcoma- a case report of an unusual entity.

BACKGROUND: Congenital alveolar rhabdomyosarcoma is an extremely uncommon and invariably fatal tumor with the current therapy. Less than 25% of patients present with evidence of cutaneous metastasis. CASE PRESENTATION: We report a case of congenital alveolar rhabdomyosarcoma in an 18-month-old male who presented with a progressively increasing mass lesion in the left post-auricular region since birth. Radiological examination did not show any intracranial involvement of the mass lesion. Upon resecting the mass that was 10-cm in largest dimension, the gross, microscopic, and ultrastructural findings were consistent with congenital alveolar rhabdomyosarcoma. CONCLUSION: The suspicion of alveolar subtype on histological grounds and proper evaluation of this tumor by immunostain and ultrastuctural examination is necessary. In the Medline literature search, there is no report of large congenital alveolar rhabdomyosarcoma in the post-auricle region.

Journal Article↗
PubMed2000

Pediatric rhabdomyosarcoma of the head and neck: is there a place for surgical management?

OBJECTIVE: To review and evaluate the place of surgical treatment in the management of rhabdomyosarcoma of the head and neck in children. DESIGN: Retrospective analysis of patient charts from January 1, 1972, to December 31, 1998. SETTING: Tertiary pediatric referral center. PATIENTS: Twenty-nine consecutive children with nonorbital head and neck rhabdomyosarcoma. INTERVENTIONS: Surgery, chemotherapy, and radiotherapy. MAIN OUTCOME MEASURES: Disease-free survival and long-term morbidity from treatment. RESULTS: Twenty patients had parameningeal and 9 had nonparameningeal head and neck tumors. All were treated with chemotherapy. For 18 patients, diagnostic biopsies were performed and they received radiotherapy. Eleven patients underwent surgery as definitive therapy. Using the Intergroup Rhabdomyosarcoma Study (IRS) staging system, 5 of these 11 patients had complete resection of tumor (IRS group I) and avoided radiotherapy. The other 6 patients required radiation because of compromised, regional, or incomplete resection of tumor. One had undergone regional resection with nodal involvement, and 2 had compromised resections with microscopic residual disease (IRS group II). Three had incomplete resections with gross residual tumor (IRS group III). Only 1 patient who underwent surgery ultimately died from recurrence at 2.7 years after an incomplete resection. The other 10 patients were relapse free at a median follow-up of 3.7 years (range 0.8-21.0 years). Long-term surgical morbidity was seen in 36% (4/11) of the patients and included facial nerve paralysis, trismus, and cosmetic deformity. CONCLUSIONS: Children with localized disease of the head and neck are able to undergo complete surgical resection, with low long-term surgical morbidity. By undergoing complete surgical resection, these children are able to avoid radiotherapy and its long-term complications, with no compromise in survival.

Child, Preschool↗
PubMed1996

Analysis of cyclin-dependent kinase inhibitor genes (CDKN2A, CDKN2B, and CDKN2C) in childhood rhabdomyosarcoma.

p16INK4A, p15INK4B, and p18 proteins are highly specific inhibitors of cyclin-dependent serine/threonine kinase (CDK) activities required for GI-S transition in the eukaryotic cell division cycle. Mutations, mainly homozygous deletions, of the CDKN2A (p16INK4A/MTSI) gene have been recently found in tumor cell lines and in many primary tumors. We looked for homozygous deletions of CDKN2A, CDKN2B (p15INK4B), and CDKN2C (p18) in 12 primary rhabdomyosarcoma (RMS) specimens and in five cell lines established from this cancer type. By means of polymerase chain reaction (PCR) and PCR-single strand conformation polymorphism (PCR-SSCP), we analyzed the presence of biallelic gene deletion or point mutation causing gene function loss. All the examined tumor cell lines (100%) and three of 12 (25%) primary tumors showed homozygous deletion of CDKN2A. Furthermore, no aberrant bands in primary tumors were detected via SSCP, suggesting the absence of mutations in the coding region. In all cases the deleted area at 9p21 also involved the CDKN2B gene. Conversely, no homozygous deletion or point mutations were detected when CDKN2C was analyzed. Our results strongly indicate that the p16INK4A (and/or p15INK4B) protein plays a key role in the development and/or progression of childhood rhabdomyosarcoma and suggest that this CDK-inhibitor protein might control proliferation and/or differentiation of human muscle cells. Moreover, alteration of CDKN2C does not appear to be involved in the genesis of rhabdomyosarcoma.

Adolescent↗
PubMed1995

Differentiation of a human rhabdomyosarcoma cell line after antineoplastic drug treatment.

The feasibility of treating solid tumours with differentiation therapy using antineoplastic drugs is currently being investigated, but the emergence of multidrug resistance remains the major limitation to this therapeutic approach. A rhabdomyosarcoma cell line resistant to actinomycin D (RD-DAC) has been used as an in vitro model to investigate, with light and electron microscopy, the degree of differentiation in multidrug-resistant cells. The parental cell line (RD), derived from a human embryonic-type rhabdomyosarcoma, is undifferentiated, with no evidence of specific ultrastructural markers. Examination of resistant cells by transmission electron microscopy revealed myofilaments arranged parallel to the long axis of the cell, which was considered clear evidence of myogenic differentiation. These observations suggest that actinomycin D, the drug of choice in the treatment of rhabdomyosarcoma, induces differentiation in the cell line RD. It is postulated that multidrug resistance can interfere with cellular differentiation.

Actin Cytoskeleton↗
PubMed2002

Actin isoform pattern expression: a tool for the diagnosis and biological characterization of human rhabdomyosarcoma.

The diagnosis and characterization of rhabdomyosarcoma requires the use of combined histological and immunohistochemical criteria due to the variety of its histological patterns. The identification of actin isoform expression is accepted as a useful adjunct to the diagnosis and classification of soft tissue tumors. Using a new antibody specific for alpha-cardiac actin, obtained according to a recently described strategy for the production of polyclonal antibodies against actin isoforms [9], we have analyzed a series of 17 rhabdomyosarcomas, including all histological subtypes. In addition, we have evaluated the presence in these tumors of alpha-skeletal and alpha-smooth muscle actins. All specimens examined revealed a positive immunostaining for alpha-cardiac actin. Tumoral cells of eight cases also expressed alpha-smooth muscle actin and only three cases (all embryonal subtypes) were positive for alpha-skeletal actin. Our results indicate that immunohistochemical screening for alpha-cardiac actin expression is a useful tool for the diagnosis of rhabdomyosarcoma. They also suggest that the expression of alpha-skeletal actin is valuable in determining the subtype and possibly the state of differentiation of these tumors.

Actins↗
PubMed2002

Cell division cycle control in embryonal and alveolar rhabdomyosarcomas.

In this study, we investigated the mRNA level of several genes involved in cell cycle regulation in alveolar (ARMS) and embryonal rhabdomyosarcomas (ERMS). p21(Cip1), Cyclin D1, Cyclin D2, Cyclin D3, CDK2, and CDK4 were evaluated by RT-PCR. All (13 out of 13) ERMS expressed the p21(Cip1) gene compared with only 40% (4 out of 10) of the ARMS. Moreover, the amount of p21(Cip1) mRNA was noticeably higher in the ERMS samples than in the positive ARMS specimens. p27(Kip1) protein were analysed by immunohistochemical and immunoblotting. A noticeable difference was observed, in that ERMS had higher amounts of the cell cycle inhibitor compared with the ARMS. Finally, treatment of two rhabdomyosarcoma cell lines, RH-30 and RD, with butyrate, resulted in complete growth inhibition and in the upregulation of the p21(Cip1) and p27(Kip1) levels. Our results demonstrate that ERMS have a much higher level of p27(Kip1) and p21(Cip1) than the alveolar types, explaining, at least in part, the distinct features and outcomes (i.e. a poor prognosis of the alveolar type) of the two forms of this childhood solid cancer. Moreover, the data on butyrate-treated cell lines suggest that the two genes are potential novel therapeutic targets for the treatment of rhabdomyosarcomas.

CDC2-CDC28 Kinases↗
PubMed2001

Detection of the PAX3-FKHR fusion gene in paediatric rhabdomyosarcoma: a reproducible predictor of outcome?

Rhabdomyosarcoma has 2 major histological subtypes, embryonal and alveolar. Alveolar histology is associated with the fusion genes PAX3-FKHR and PAX7-FKHR. Definition of alveolar has been complicated by changes in terminology and subjectivity. It is currently unclear whether adverse clinical behaviour is better predicted by the presence of these fusion genes or by alveolar histology. We have determined the presence of the PAX3/7-FKHR fusion genes in 91 primary rhabdomyosarcoma tumours using a combination of classical cytogenetics, FISH and RT-PCR, with a view to determining the clinical characteristics of tumours with and without the characteristic translocations. There were 37 patients with t(2;13)/PAX3-FKHR, 8 with t(1;13) PAX7-FKHR and 46 with neither translocation. One or other of the characteristic translocations was found in 31/38 (82%) of alveolar cases. Univariate survival analysis revealed the presence of the translocation t(2;13)/PAX3-FKHR to be an adverse prognostic factor. With the difficulties in morphological diagnosis of alveolar rhabdomyosarcoma on increasingly used small needle biopsy specimens, these data suggest that molecular analysis for PAX3-FKHR will be a clinically useful tool in treatment stratification in the future. This hypothesis requires testing in a prospective study. Variant t(1;13)/PAX7-FKHR appears biologically different, occurring in younger patients with more localised disease.

Adolescent↗
PubMedDate not supplied

Soft-tissue sarcomas of the diaphragm: a report from the Intergroup Rhabdomyosarcoma Study Group from 1972 to 1997.

PURPOSE: To describe clinical details and outcome of children and adolescents with primary sarcomas of the diaphragm treated on Intergroup Rhabdomyosarcoma Studies (IRS) I through IV. PATIENTS AND METHODS: We reviewed the records of 15 patients with sarcoma of the diaphragm who were entered on IRS Group protocols between 1972 and 1997. Patient ages at diagnosis ranged from 0.5 to 20 years (median, 13 yrs), and 10 were girls. Patients had chest pain, dyspnea, and/or coughing, decreased breath sounds, and occasionally hepatomegaly. RESULTS: Localized, gross residual disease after initial surgery was present in 10 patients, and five had metastases at diagnosis (pleura, 3; pericardium, 1; lungs and bones, 1). Tumor subtypes were alveolar rhabdomyosarcoma (RMS) in five cases, embryonal RMS in three, undifferentiated sarcoma in three, extraosseous Ewing sarcoma in three, and unclassified sarcoma in one. Treatment consisted of radiation therapy to the primary tumor and metastases when feasible, and combination chemotherapy with vincristine, actinomycin D, and cyclophosphamide with or without doxorubicin, ifosfamide, cisplatin, and etoposide. Ten patients achieved complete remission (67%), four obtained a partial remission, and one was improved. Five patients (33%) are continuously failure-free and alive at a median of 8.8 years from diagnosis (range, 1.1-15 yrs). However, the other 10 patients experienced relapse at 0.3 to 2 years from start of therapy (median, 1 yr). Sites of relapse were local in five, distant in three, and combined in two. Death after relapse occurred at 0.39 to 2.6 years (median, 1.6 yrs) from diagnosis. CONCLUSIONS: Sarcomas of the diaphragm are generally deemed unresectable at diagnosis and/or are metastatic. Most of them are not embryonal rhabdomyosarcomas. Treatment with more effective primary chemotherapy to shrink the tumor, followed-up by surgical resection and radiation therapy, should improve the prognosis for patients with sarcomas arising in the diaphragm, especially for the majority who have localized tumors.

Adolescent↗
PubMed2002

The expression of WT1 in the differentiation of rhabdomyosarcoma from other pediatric small round blue cell tumors.

The WT1 gene encodes a transcription factor implicated in normal and neoplastic development. The purpose of this study was to evaluate the diagnostic utility of a commercial WT1 antibody on a variety of pediatric small round blue cell tumors (SRBCT). A mouse monoclonal antibody (clone: 6F-H2, DAKO) raised against the N-terminal amino acids 1-181 of the human WT1 protein was tested. Microscopic sections from 66 specimens were stained using an antigen retrieval protocol with trypsin. The tumors included peripheral neuroectodermal tumors (PNET/Ewing's), neuroblastomas, desmoplastic small round cell tumors (DSRCT), lymphomas, Wilms' tumors, and rhabdomyosarcomas (RMS). One RMS case was investigated by Western blot analysis and RT-PCR to confirm the antibody specificity. A strong cytoplasmic staining was demonstrated in all RMS (11/11). The Western blot analysis confirmed the WT1 protein in the tissue, and the RT-PCR confirmed the presence of WT1 mRNA in the peripheral blood and tissue of one RMS patient. The Wilms' tumors had a variable nuclear and/or cytoplasmic positivity in most (17/24) cases. All PNET/Ewing's were negative. The nuclei of two lymphoblastic lymphomas stained strongly. A weak nuclear or cytoplasmic staining was reported in a few DSRCT (3/5), lymphomas (2/10), and neuroblastomas (2/8). This is a useful antibody in the differentiation of RMS from other SRBCTs. A strong cytoplasmic staining favors an RMS, and a strong nuclear staining is suggestive of a Wilms' tumor. A role for WT1 in the pathogenesis of rhabdomyosarcomas is raised. The limited sampling precludes any conclusions regarding the value of tissue or peripheral blood analysis for WT1 mRNA in patients with rhabdomyosarcoma.

Animals↗