An intra-abdominal small round cell neoplasm with features of primitive neuroectodermal and desmoplastic round cell tumor and a EWS/FLI-1 fusion transcript

Primary Desmoplastic Small Round Cell Tumor of the Femur: Case Report and Review of a Rare Intraosseous Malignancy

Background: Desmoplastic small round cell tumors (DSRCT) are malignant neoplasms of young males arising most commonly in the abdominopelvic cavity, with a subset originating from extra-abdominal soft tissues. As either primary or metastatic lesions, they are rare in intraosseous sites. Case Presentation: We describe the fifth report of primary DSRCT of bone. A healthy 18-year old male presented with a blastic, 17 cm lesion within the left distal femur, suspicious for osteosarcoma or Ewing sarcoma. Subsequent biopsy revealed nests of small round blue cells infiltrating through a desmoplastic stroma. These cells were diffusely positive for epithelial markers, with paranuclear staining for desmin and focal reactivity with NSE. Break-apart FISH revealed a rearrangement in EWSR1, and RNA fusion panel confirmed WT1 as its partner in the pathognomonic t(11;22)(p13;q12) rearrangement. PET/CT showed widespread metastatic disease to visceral and bony sites. Conclusions: Due to their rarity as well as clinicopathologic and immunomorphologic overlap, primary intraosseous DSRCT can create diagnostic challenges with the more frequently encountered tumors of bone.

Desmoplastic small round cell tumor of the kidney: a case report

Background

Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive neoplasm seen in children and young adults, usually manifested by involvement of abdominal serosa. Here, we present an unusual case of primary DSRCT of kidney.

Case presentation

The patient was an 8-year-old girl with a large renal mass which was confused with primitive neuroectodermal tumor (PNET) in the needle biopsy. The tumor had a variegated histology revealing frequent pseudo-rosette formations, pseudopapillary architecture, rhabdoid, clear or pleomorphic cells in addition to typical small round cell morphology and desmoplasia. It showed immunohistochemical features of DSRCT, and EWSR1 re-arrangement.

Conclusions

Proffering this diagnosis is particularly difficult for tumors of viscera because of the incognizance of the entity in these locations. Moreover, DSRCT is a great mimicker and may get easily confused with more common kidney malignancies of childhood such as Wilms tumor, PNET/EWS, rhabdoid tumor, clear cell sarcoma, and other small round cell tumors as well as renal cell carcinomas. The distinction is critical as the accurate therapeutic approach will require correct diagnosis.

Ewing Sarcoma and the History of Similar and Possibly Related Small Round Cell Tumors: From Whence Have We Come and Where are We Going?

The diagnosis of small round cell tumors always has been extremely difficult, and our current classification systems continue to evolve. Since its initial discovery by Dr James Ewing, the historical context of what is acceptably included under the designation "Ewing sarcoma" has changed. Although Ewing sarcoma and primitive neuroectodermal tumor were both initially described in the early 20th century, these tumors were considered likely distinct entities until the end of that same century, almost 75 years later. With modern immunohistochemistry and more recent advances in molecular techniques, the understanding of Ewing sarcoma and Ewing-like tumors has improved dramatically but also raises new questions and challenges. We now know that this category of tumors is remarkably more heterogenous than initially thought, especially in regards to its cytogenetics and molecular properties, and some of these differences likely have prognostic relevance. Whether we are now expanding the spectrum of Ewing sarcoma or simply recognizing new entities is controversial. Therapeutic approaches to address these new categories and/or entities need further focus and attention. Herein, we provide a comprehensive historical perspective on Ewing sarcoma, Ewing-like tumors (CIC and BCOR-rearranged sarcomas), and related and/or similar small round cell tumors, often included in the differential diagnosis, including mesenchymal chondrosarcoma, desmoplastic small round cell tumor, and small cell osteosarcoma. We also seek to provide updates and insights into the evolving classification and clinical relevance of the Ewing family of tumors.

INI1-deficient tumors: diagnostic features and molecular genetics

Significant progress has been made in understanding the molecular genetic alterations involved in sarcomagenesis. Cytogenetic and molecular studies have identified nonrandom genetic abnormalities, including tumor suppressor gene inactivation. Mutations, deletions, and other somatic alterations in the tumor suppressor gene INI1 (hSNF5; SMARCB1), which encodes a subunit of the SWI/SNF chromatin remodeling complex, were first described in the malignant rhabdoid tumor of infancy. Since then, INI1 has also been implicated in the pathogenesis of additional tumor types including renal medullary carcinomas and epithelioid sarcomas and a subset of epithelioid malignant peripheral nerve sheath tumors, myoepithelial carcinomas, and extraskeletal myxoid chondrosarcomas. As varied as this group appears, they all show loss of INI1 protein expression, a propensity for rhabdoid cytomorphology, and sometimes other overlapping immunohistochemical and histologic findings. We will review the clinicopathologic features of these tumor types and emphasize the clinical utility of INI1 immunohistochemistry in differential diagnosis.

Uncommon presentation of rare disorder-duodenal ulcer secondary to invasive pancreatic primitive neuroectodermal tumor: case report and review of the literature

The authors report an unusual presentation of a rare tumor in childhood, a pancreatic primitive neuroectodermal tumor invading the duodenum leading to anemia. A review of intra-abdominal primitive neuroectodermal tumors is discussed.

Pathobiologic markers of the ewing sarcoma family of tumors: state of the art and prediction of behaviour

Over the past three decades, the outcome of Ewing sarcoma family tumor (ESFT) patients who are nonmetastatic at presentation has improved considerably. The prognosis of patients with metastatic disease at the time of diagnosis and recurrence after therapy remains dismal. Drug-resistant disease at diagnosis or at relapse remains a major cause of mortality among patients diagnosed with ESFT. In order to improve the outcome for patients with potential relapse, there is an urgent need to find reliable markers that either predict tumor behaviour at diagnosis or identify therapeutic molecular targets at the time of recurrence. An improved understanding of the cell of origin and the molecular pathways that regulate tumorigenicity in ESFT should aid us in the search for novel therapies for ESFT. The purpose of this paper is thus to outline current concepts of sarcomagenesis in ESFT and to discuss ESFT patterns of differentiation and molecular markers that might affect prognosis or direct future therapeutic development.

Impact of abdominopelvic CT on Ewing sarcoma management

RATIONALE AND OBJECTIVES

Abdominopelvic computed tomography (APCT) is often performed in patients with skeletal Ewing sarcoma family of tumors during initial staging and for subsequent clinical indications, such as metastasis surveillance; however, its clinical impact is unknown. The purpose of this study was to evaluate whether these computed tomographic examinations alter oncologic management and therefore patient outcomes.

MATERIALS AND METHODS

One hundred eight consecutive patients with skeletal Ewing sarcoma family of tumors seen from 1985 to 2008 were retrospectively reviewed to identify imaging workup, pathology, primary site, evidence of metastatic disease, and patient outcomes. Data were analyzed using Wilcoxon's rank sum tests.

RESULTS

Sixty-five of the 108 patients (60%) underwent 342 abdominopelvic computed tomographic examinations during a mean follow-up period of 8.9 years. During this time period, only one of the 65 patients (1.5%) who underwent APCT was discovered to have abdominal metastatic disease. There was no significant difference in the incidence of metastatic disease to the skeleton or chest between the groups without and with APCT (P = .10). There were 26 pelvic and lumbosacral primaries (24%) and 82 limb primaries (76%). Subgroup analysis performed on the 82 patients with limb primaries without (n = 36) and with (n = 46) APCT showed no significant differences in metastatic incidence to the skeleton or chest (P = .14).

CONCLUSIONS

This study indicates that APCT, associated with increased radiation exposure and health expenditure, has a limited role in initial staging and follow-up in patients with skeletal Ewing sarcoma, particularly in patients with limb primaries.

Modern Diagnosis of Small Cell Malignancies of Children

Small cell malignancies of children constitute a continuing diagnostic challenge for surgical pathologists, although modern methods of ancillary diagnosis provide powerful tools that resolve most difficult cases. Current techniques range from identification of DNA alternations, including gene fusions, chromosome translocations, and genetic deletions, to recognition of characteristic patterns of protein expression, usually visualized with immunohistochemistry. In spite of these advances, recognition of key cellular and histologic features remains the keystone of diagnosis but requires adequately fixed and carefully stained histologic sections. Cytologic features now suffice for diagnosis if confirmed by appropriate testing. This article outlines key histologic features of pediatric small cell neoplasms and the algorithms that allow diagnostic confirmation and the initiation of appropriate therapy.

Soft tissue tumors associated with EWSR1 translocation

The Ewing sarcoma breakpoint region 1 (EWSR1; also known as EWS) represents one of the most commonly involved genes in sarcoma translocations. In fact, it is involved in a broad variety of mesenchymal lesions which includes Ewing's sarcoma/peripheral neuroectodermal tumor, desmoplastic small round cell tumor,clear cell sarcoma, angiomatoid fibrous histiocytoma, extraskeletal myxoid chondrosarcoma, and a subset of myxoid liposarcoma. The fusion products between EWSR1 and partners usually results in fusion of the N-terminal transcription-activating domain of EWSR1 and the C-terminal DNA-binding domain of the fusion partner, eventually generating novel transcription factors. EWSR1 rearrangement can be visualized by the means of fluorescence in situ hybridization (FISH). As soft tissue sarcomas represent a diagnostically challenging group, FISH analysis is an extremely useful confirmatory diagnostic tool. However, as in most instances a split-apart approach is used, the results of molecular genetics must be evaluated in context with morphology.

[Cystic desmoplastic small round cell tumor: tumor development from cystic-"mesothelioblastic" areas?]

A 7-cm cystic lesion in the upper left abdomen and additional smaller solid tumor nodules were diagnosed incidentally in a 15-year-old boy without tumor symptoms. The main tumorous cystic lesion showed a flattened single-cell tumor cell component in gradual transition to stratified, papillary and truly "invasive" typical desmoplastic areas of a desmoplastic small round-cell tumor (DSRCT). The Ki-67-proliferation index gradually increased within three histologic tumor patterns up to about 70% in the typical desmoplastic (infiltrating) component. Using microdissection techniques, EWS-WT1-gene fusion transcripts were detected in the cystic (single-cell-layered), the papillary and the solid tumor proliferations (exon 7 of EWS on chromosome 22 with exon 8 of WT1 on chromosome 11). The presented case illustrates a predominant cystic growth pattern of DSRCT, in which a stepwise development in the pathogenesis of DSRCT from cystic (-"mesothelioblastic") towards a more papillary proliferation and finally typical "infiltrative" desmoplastic tumor pattern might be discussed. The cystic pattern could represent an initial stage in the development of the neoplasia. The presence of specific EWS-WT1-gene fusion transcripts in all tumor growth patterns in this respect would indicate an early event in t(11;22)(p13;q12) translocation in the pathogenesis of DSRCT.

Desmoplastic small round cell tumor of the central nervous system: report of two cases and review of the literature

Desmoplastic small round cell tumor (DSRCT) is a malignant tumor often involving the abdominal and/or pelvic peritoneum. Only one fully documented example has arisen in the central nervous system (CNS). Herein, we describe two additional examples, fulfilling the morphologic, immunohistochemical, and molecular criteria (EWS/WT1 translocation) of DSRCT. Both arose in the cerebellopontine angle (CPA) and underwent spinal dissemination. Patient 1, a 37-year-old male, underwent a subtotal resection, and 2 years later died of recurrent disease with spinal dissemination. Patient 2, a 39-year-old man, presented with cerebellar and CPA lesions as well as spinal leptomeningeal deposits. After 27 months of adjuvant therapy, he is alive with progressive disease. In conclusion, CNS DSRCT follows a similar aggressive course as do peritoneal examples. Although rare, DSRCT warrants consideration in the differential diagnosis of "malignant small blue cell tumors" of the CNS.

Immunophenotyping of Tumours

BACKGROUND

Immunophenotyping has added a new dimension to improve the diagnostic accuracy of malignant diseases. The emphasis is on its usefulness in planning and institution of specific therapy besides helping in prognostication.

METHODS

The study included 83/1385 biopsies of cancer patients over an 18 month period on which immunohistochemical staining (IHC) with monoclonal antibodies were performed. The technique was used to establish the histogenetic origins/expression of the tumours. The study excluded haematolymphoid malignancies.

RESULT

Eighty three cases on whom IHC was performed included poorly differentiated tumours (15), metastatic tumours (16), soft tissue tumours (35), central nervous system tumours (9) and miscellaneous (6). Two cases could not be typed. The clinicopathological correlation in terms of the management and the problems related to its misinterpretation are discussed.

CONCLUSION

Immunophenotyping of tumours in an oncology set up is significant in the 'Final Diagnosis'.

Primary primitive neuroectodermal tumor of the uterus: a case report

Neuroendocrine carcinomas primitive neuroectodermal tumor (PNET) arise from Kulchitsky cells and are frequently seen in gastrointestinal tract and lungs. But they are unusual in gynecology practice. We presented a case of PNET arising in the uterine corpus of a 22-year-old woman. To our knowledge, this is the first description of small-cell carcinoma of the uterine corpus with a pseudocyst formation within the myometrium without endometrial invasion.

Intra-abdominal desmoplastic small round cell tumor: an analysis of 4 cases

AIM: To investigate the clinical features of intra-abdominal desmoplastic small round cell tumor (IDSRCT).

METHODS: We retrospectively analyzed 4 cases of IDSRCT in our hospital from June 1996 to October 2006.

RESULTS: All the 4 cases were admitted with symptoms of ascites and/or abdominal mass. The patients underwent exploratory laparotomy, revealing multiple peritoneal and mesenteric masses with an extensive seeding. The diagnosis was made by pathology after operation.

CONCLUSION: IDSRCT is a very rare peritoneal malignant neoplasm, and it is a disease with high metastasis and poor prognosis.

Differentiating Ewing's sarcoma from other round blue cell tumors using a RT-PCR translocation panel on formalin-fixed paraffin-embedded tissues

Ewing's sarcoma is a common malignancy of bone and soft tissue that occurs most often in children and young adults. Differentiating Ewing's sarcoma from other round blue cell tumors can be a diagnostic challenge because of their similarity in histology and clinical presentation. Thus, ancillary molecular tests for detecting disease-defining translocations are important for confirming the diagnosis. We analyzed 65 round blue cell tumors, including 53 Ewing's sarcoma samples from 50 unique cases. Samples were processed for RNA from archived formalin-fixed paraffin-embedded tissue blocks. Real-time RT-PCR assays specific for Ewing's sarcoma (EWS-FLI1, EWS-ERG, EWS-ETV1, EWS-ETV4, and EWS-FEV), synovial sarcoma (SYT-SSX1 and SYT-SSX2), and rhabdomyosarcoma (PAX3-FKHR and PAX7-FKHR) were tested across the samples. The translocation panel had a sensitivity of 81% (43 out of 53 samples) for diagnosing Ewing's sarcoma when using the histological criteria as the 'gold' standard. None of the Ewing's specific translocations were found in the non-Ewing's samples (100% specificity). Of the 43 samples with translocations detected, 26 (60%) had an EWS-FLI1 type 1 translocation, 13 (30%) had an EWS-FLI1 type 2 translocation, 3 (7%) had an EWS-ERG translocation, 1 had an EWS-ETV1 translocation, and 1 sample had both an EWS-FLI1 type 1 and type 2 translocation. Our real-time RT-PCR assay for detecting sarcoma translocations has high sensitivity and specificity for Ewing's sarcoma and has clinical utility in differentiating small round blue cell tumors in the clinical lab.

Metastatic primitive neuroectodermal tumor of the ovary in pregnancy

Primitive neuroectodermal tumor (PNET) is a small round tumor belonging to the PNET/Ewing's sarcoma family. We hereby report a case of PNET of the ovary, which was detected at the second trimester of pregnancy. Chemotherapy was administered and a healthy baby was delivered by cesarean section. After the pregnancy, the mother was found to have metastatic disease. Chemotherapy was continued, but she died due to progressive disease 13 months after the initial diagnosis. In this case report, we discuss chemotherapy options during pregnancy and the importance of multidisciplinary approach to unusual presentations of rare tumors.

Type 1 (11; 22)(q24: q12) translocation is common in Ewing’s sarcoma/ peripheral neuroectodermal tumour in south Indian patients

The Ewing's sarcoma family can present diagnostic difficulties. In the past the basis of diagnosis has been a exclusion. Identification of a specific translocation especially t(11;22) (EWS-FLI 1 fusion gene), which is seen in nearly 85 percent of Ewing's sarcoma cases can help in precise diagnosis. We have carried out a study on twenty patient samples diagnosed to have Ewing's sarcoma/peripheral neuroectodermal tumour (PNET)/small round cell malignant tumour. The study involved RT-PCR analysis for the fusion transcript, followed by sequencing to identify the specific type of fusion. Ninety percent (18/20) of the samples tested were found to be t(11;22) translocations involving EWS-FLI 1 genes. Sixty-one percent (11/18) were found to be type 1 fusion and seven were type 2 (39 percentage). This is the first study in India with quantitative information about the types of EWS-FLI 1 translocations present in Ewing's family of tumours in south Indian patients.

Immunohistochemical findings in embryonal small round cell tumors with molecular diagnostic confirmation

The diagnosis of pediatric tumors relies heavily on immunohistochemical staining of small tissue biopsies, since many entities share a "small blue cell" phenotype. More recently, molecular genetic analysis for detection of specific gene fusion products has become available. With the increased use of such molecular techniques, the authors have noted that tumors with proven molecular diagnoses can exhibit unusual patterns of immunohistochemical staining. This study examines pediatric tumors with a "small blue cell" phenotype in which molecular diagnoses were available where applicable. A panel of immunohistochemical stains was performed (S100, CD56, NB84, CD99 [MIC2], Bcl-2, CD117, CD34, desmin, MNF116, and WT1). In the 370 sections from 37 cases, all primitive neuroectodermal tumors, with and without the presence of t(11;22), demonstrated uniform membranous membrane staining with CD99 (MIC2) and focal staining with CD56, NB84, MNF116, and WT1. All rhabdomyosarcomas, both alveolar and embryonal, demonstrated uniform desmin, CD56, and cytoplasmic WT1 immunostaining. Desmoplastic small round cell tumors showed positive cytokeratin staining, with half having "dot-like" cytoplasmic desmin and WT1 positivity; some showed focal positivity for NB84, CD99, and Bcl-2. The "undifferentiated" sarcomas showed the widest range of staining, with no marker staining all cases. Neuroblastomas exhibited uniform strong staining for CD56 and NB84 and marked cytoplasmic Bcl-2 positivity, and some cases showed cytoplasmic WT1 expression. Blastematous Wilms' tumors showed uniform strong membranous staining for CD56, uniform cytoplasmic staining for Bcl-2, and nuclear expression of WT1. Embryonal pediatric malignancies can demonstrate apparently nonspecific expression patterns for several antigens, which may reflect developmental immaturity rather than specific differentiation pathways.

Primary desmoplastic small round cell tumor of bone: report of a case with cytogenetic confirmation

We report a case of desmoplastic small round cell tumor occurring in the right ilium of a 13-year-old boy. Morphologically, the neoplasm consisted of small round cells of primitive appearance with a diffuse growth pattern replacing marrow space and eroding bone. Immunohistochemical staining was positive for vimentin, synapsin, CD99 (MIC2 protein), and FLI-1, prompting an initial diagnosis of Ewing sarcoma/primitive neuroectodermal tumor. However, a diagnosis of desmoplastic small round cell tumor was rendered after the detection by cytogenetic analysis of the reciprocal chromosomal translocation, t(11;22)(p13;q12), which is uniquely associated with this tumor. This is the first documented instance of desmoplastic small round cell tumor arising in bone.

Peripheral primitive neuroectodermal tumor of the stomach in a 14-year-old boy: a case report

Although PNETs are rare malignancies, they should be considered in the differential diagnosis of submucosal gastric tumours in adolescents with clinical alarm symptoms.NET was confirmed by detection of the characteristic EWS/FLI-1 fusion gene, resulting in a reciprocal translocation t(11;22)(q24;q12). Three distinct liver metastases were detected by CT, MRI, and PET. The tumour failed to respond to neoadjuvant polychemotherapy with vincristine, etoposide, doxorubicin, and ifosfamide. Subtotal gastrectomy was performed and, surprisingly, we found diffuse metastatic infiltration of the liver that had not been detected by preoperative staging. Due to the diffuse metastatic disease the young patient's prognosis has to be considered very poor. Because of the tumour's intense expression of CD117 (c-kit), the patient is now treated with the tyrosine kinase inhibitor imatinib (STI571).

Ewing sarcoma/peripheral primitive neuroectodermal tumor: adult abdominal tumors with an Ewing sarcoma gene rearrangement demonstrated by fluorescence in situ hybridization in paraffin sections

The differential diagnosis of small round cell tumors is exhaustive and requires ancillary studies. Relatively recently, fluorescence in situ hybridization (FISH) using probes for specific gene rearrangements has gained wide acceptance. This technique is particularly useful in the differential diagnosis of Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET) and desmoplastic small round-cell tumor (DSRCT). In ES/PNET, the EWS gene is juxtaposed to the FLI-1 gene in 85% of cases and to the ERG gene in another 7% of cases; the EWS gene is juxtaposed to the WTI gene in DSRCT. Documentation of the EWS gene rearrangements in EWS/PNET has previously been demonstrated in frozen tissue. We report 2 unusual cases of EWS/PNET diagnosed in abdominal tumors in adults. Although the immunohistochemical results supported a diagnosis of ES/PNET, 1 case morphologically resembled DSRCT. The diagnosis in these 2 cases was confirmed by the FISH demonstration of EWS/FLI-1 gene fusion in paraffin-embedded tissue. Thus, the usefulness of FISH demonstration of an EWS gene rearrangement with these specific probes in such unusual cases is supported and is demonstrated in paraffin-embedded tissue.

Practical application of molecular genetic testing as an aid to the surgical pathologic diagnosis of sarcomas: a prospective study

The strong correlation of specific reciprocal translocations with individual tumor types and the demonstration that polymerase chain reaction (PCR)-based methods can detect translocations in tissue samples have stimulated interest in the role of molecular genetic testing in diagnostic surgical pathology. To evaluate the clinical utility of PCR-based molecular analysis of soft tissue neoplasms in routine surgical pathology, 131 consecutive soft tissue tumors submitted for molecular genetic testing at a tertiary care teaching hospital were prospectively analyzed over a 36-month period. RT-PCR was used to test tumor RNA for fusion transcripts characteristic of malignant round cell tumors (including Ewing sarcoma/primitive neuroectodermal tumor, desmoplastic small round cell tumor, and alveolar rhabdomyosarcoma), spindle cell tumors (including synovial sarcoma and congenital fibrosarcoma), and fatty tumors (myxoid liposarcoma). DNA sequence analysis was used to confirm the identity of all PCR products, and the PCR results were compared with the histopathologic diagnosis. We found that sufficient RNA for RT-PCR-based testing was recovered from 96% of the 131 cases and the percentage of tumors that tested positive for the associated characteristic fusion transcript was in general agreement with those reported in the literature. DNA sequence analysis of PCR products identified both variant transcripts and spurious PCR products, underscoring the value of product confirmation steps when testing formalin-fixed, paraffin-embedded tissue. Only in rare cases did testing yield a genetic result that was discordant with the histopathologic diagnosis. We conclude that PCR-based testing is a useful adjunct for the diagnosis of malignant small round cell tumors, spindle cell tumors, and other miscellaneous neoplasms in routine surgical pathology practice.

Desmoplastic small round cell tumor: a clinicopathologic, immunohistochemical, and molecular study of 32 tumors

Desmoplastic small round cell tumor is a rare, aggressive neoplasm that mainly affects young male patients and is characterized by a reciprocal translocation t(11;22)(p13;q12) associated with the EWS-WT1 gene fusion transcript. Clinical, histopathologic, immunohistochemical, and molecular genetics features were reviewed for 32 tumors. There were 29 male and three female patients, with ages from 6 to 54 years (mean, 25 years). The main clinical signs and symptoms included abdominal pain (eight patients), weight loss (five patients), and presence of umbilical hernia (four patients). Two tumors primarily involved the ethmoid sinus and the soft tissues of the scalp; the other tumors (mean size, 10 cm) involved the abdominal cavity (88%). One patient presented initially with an axillary lymph node metastasis. Generally, all tumors showed the typical histologic findings of variably sized clusters of small, round, or spindled cells lying in a desmoplastic stroma. The neoplastic cells in formalin-fixed, paraffin-embedded tissue sections were positive for desmin (dot pattern) (81% of the cases), WT1 (91%), keratin (87%), neuron-specific enolase (84%), CD99 (23%), and actin (3%). The EWS-WT1 gene fusion transcript was detected in 29 of 30 tumors. One tumor with typical clinicopathologic and immunohistochemical features did not show the gene fusion. Follow-up for 27 patients showed that 19 patients (70%) died of uncontrolled, local, or widespread metastatic disease 3-46 months (mean, 20 months) after diagnosis, and eight patients were alive with known evidence of disease. Occasionally, desmoplastic small round cell tumor lacks the classic clinical, histologic, and immunohistochemical features. This study emphasizes the utility of analysis of the EWS-WT1 gene fusion transcript, which was performed on paraffin-embedded tissues, to confirm the diagnosis.

Magnetic resonance imaging of nongynecologic pelvic masses in children

Pelvic neoplasms can arise from the genitourinary tract, gonads, soft tissues, or bone. The role of imaging is to confirm the presence of tumor, determine the site of origin, delineate the extent for staging and treatment planning, and serve as a baseline for monitoring response to therapy. MR imaging is well suited for the characterization and staging of pediatric pelvic tumors. This article reviews the imaging findings and staging evaluation of the common nongynecologic neoplasms in children. Prostatic, bladder, gonadal, and sacrococcygeal tumors are discussed. Gynecologic tumors are discussed elsewhere in this issue.

Molecular genetic analysis of a small bowel primitive neuroectodermal tumor

We present a pediatric peripheral primitive neuroectodermal tumor (pPNET) localized exclusively to the small bowel. The tumor presented in an adolescent male and the diagnosis was confirmed by electron microscopy, CD99 immunopositivity, and molecular genetic analysis that demonstrated an EWS-FLI1 type 2 fusion transcript. This case report and a review of the literature underscore the considerable phenotypic overlap in EWS-related tumors in this site and the necessity for molecular genetic analysis to permit accurate classification.

Transdifferentiation of neoplastic cells

Transdifferentiation is a process in which a stable cell's phenotype changes to that of a distinctly different cell type. It occurs during certain physiological processes and leads to transition of tumor cell phenotypes. The latter process includes neoplastic epithelial-epithelial transition, neoplastic epithelial-mesenchymal transition, neoplastic mesenchymal-epithelial transition and transition between non-neural and neural neoplastic cell. This phonomenon is exemplified in some origin-debated tumors, such as carcinosarcoma, pleomorphic adenoma, synovial sarcoma, Ewing's/pPNET, and malignant fibrohistiocytoma. We propose that differentiation disturbance of cancer cells should include not only undifferentiation and dedifferentiation, but also transdifferentiation as well. Tumor cell transdifferentiation may be influenced or determined by cellular genetic instabilities, proliferation and apoptosis, as well as by extracellular matrix and growth factors.

Molecular genetic aspects of solid tumors in childhood

Advances in molecular genetic research in the past 2 decades have led to an increased understanding of the genetic events in the pathogenesis and progression of human malignancies, including those of childhood. A number of pediatric malignancies have served as models for the molecular genetic approach to patients with cancer. These have highlighted the utility of molecular analysis for a variety of purposes including diagnosis, risk stratification and treatment planning, understanding of syndromes associated with cancer and genetic screening, genetic counseling and prophylactic treatment including surgery. It is likely that there soon will be individualized treatment regimens based on the molecular biologic profile of a patient's tumor. In addition, molecular profiling will lead to new drug development designed to induce differentiation of tumor cells, block dysregulated growth pathways, or reactivate silenced apoptotic pathways. This review discusses the molecular genetic aspects of some of the more common pediatric tumors as well as tumors whose pathogenetic mechanisms are particularly instructive.

Primitive neuroectodermal tumors of the biliary and gastrointestinal tracts: clinicopathologic and molecular diagnostic study of two cases

Primitive neuroectodermal tumor (PNET) is a prototypic malignant small round cell tumor of childhood that is characterized in most cases by t(11;22) resulting in an EWS-FLI1 gene fusion. Once thought to be uncommon, PNET now accounts for almost 20% of malignant soft tissue tumors in children. Increased recognition of PNET is partly due to advances in immunohistochemistry and molecular diagnostics, which have led to the identification of the tumor in non-classical sites. We report the clinical, histologic, immunohistochemical, and molecular findings of two visceral PNETs of the digestive system--one involving the small intestine and the other involving the hepatic duct. Histologically, each tumor was composed of malignant small cells growing in sheets, nests, and lobules; the tumor cells of both cases showed characteristic immunoreactivity for vimentin and O13 (CD99). Reverse transcription-polymerase chain reaction (RT-PCR) analysis for t(11;22) using nested primers was performed with RNA extracted from paraffin-embedded, formalin-fixed tissue and demonstrated an EWS exon 7 to FLI1 exon 5 fusion in both cases, confirmed by Southern blot hybridization and DNA sequence analysis. These results illustrate the expanded clinicopathologic profile of PNET, and demonstrate that visceral PNETs, despite their unusual sites of presentation, maintain the characteristic immunohistochemical and genetic features of PNETs at more conventional sites.

Targeted deletion of the gene encoding iron regulatory protein-2 causes misregulation of iron metabolism and neurodegenerative disease in mice

In mammalian cells, regulation of the expression of proteins involved in iron metabolism is achieved through interactions of iron-sensing proteins known as iron regulatory proteins (IRPs), with transcripts that contain RNA stem-loop structures referred to as iron responsive elements (IREs). Two distinct but highly homologous proteins, IRP1 and IRP2, bind IREs with high affinity when cells are depleted of iron, inhibiting translation of some transcripts, such as ferritin, or turnover of others, such as the transferrin receptor (TFRC). IRPs sense cytosolic iron levels and modify expression of proteins involved in iron uptake, export and sequestration according to the needs of individual cells. Here we generate mice with a targeted disruption of the gene encoding Irp2 (Ireb2). These mutant mice misregulate iron metabolism in the intestinal mucosa and the central nervous system. In adulthood, Ireb2(-/-) mice develop a movement disorder characterized by ataxia, bradykinesia and tremor. Significant accumulations of iron in white matter tracts and nuclei throughout the brain precede the onset of neurodegeneration and movement disorder symptoms by many months. Ferric iron accumulates in the cytosol of neurons and oligodendrocytes in distinctive regions of the brain. Abnormal accumulations of ferritin colocalize with iron accumulations in populations of neurons that degenerate, and iron-laden oligodendrocytes accumulate ubiquitin-positive inclusions. Thus, misregulation of iron metabolism leads to neurodegenerative disease in Ireb2(-/-) mice and may contribute to the pathogenesis of comparable human neurodegenerative diseases.

Immunohistochemical detection of FLI-1 protein expression: a study of 132 round cell tumors with emphasis on CD99-positive mimics of Ewing's sarcoma/primitive neuroectodermal tumor

The histologic and immunohistochemical differentiation of Ewing' s sarcoma/primitive neuroectodermal tumor (ES/PNET) from other small, blue, round cell tumors may be difficult. Despite initial promise, CD99 (MIC2) has not proven to be a specific marker. Approximately 90% of ES/PNET have a specific t(11; 22)(q24;q12) that results in fusion of the EWS and FLI-1 genes, and overexpression of FLI-1 protein. A recent study has shown immunohistochemical FLI-1 expression in five of seven of the ES/PNET cases tested. We evaluated FLI-1 expression in 132 well-characterized small, blue, round cell tumors. All tumors were immunostained for FLI-1 (1:40, Sc 356 polyclonal, Santa Cruz Biotechnology) using steam heat for epitope retrieval. Only nuclear staining was accepted as positive. Endothelial cells were strongly positive in all cases and served as an internal control. In many cases, a subset of lymphocytes also stained positive. No staining was seen in any other normal tissue. FLI-1 expression was seen in 29 of 41 (71%) ES/PNET, 7 of 8 (88%) lymphoblastic lymphomas, 0 of 8 poorly differentiated synovial sarcomas (PDSS), 0 of 32 rhabdomyosarcoma (RMS), 0 of 30 neuroblastomas, 0 of 8 esthesioneuroblastomas, 0 of 3 Wilms' tumors, 0 of 1 mesenchymal chondrosarcoma, and in 1 of 1 desmoplastic round cell tumor. This last case was known to have an EWS/WT-1 fusion. Although the EWS/FLI-1 fusion gene is specific for ES/PNET, FLI-1 protein expression is not. Significantly, the great majority of lymphoblastic lymphomas (also CD99-positive) are strongly FLI-1-positive. Immunohistochemical detection of FLI-1 may be valuable in confirming the diagnosis of ES/ PNET in cases in which molecular genetic evaluation is not feasible. FLI-1 protein expression is also helpful in distinguishing ES/PNET from other tumors that may be CD99-positive, such as PDSS and RMS. It is not surprising that some ES/ PNET are FLI-1-negative, because not all ES/PNET have the classic EWS/FLI-1, and some cases of ES/PNET may produce either low levels of protein or idiotypically different protein.

A novel zinc finger gene is fused to EWS in small round cell tumor

Ewing sarcoma family of tumors share recurrent translocations that fuse EWS from 22q12 to five different members of transcription factors namely FLI-1, ERG, ETV1, E1AF and FEV. Different classes of DNA binding proteins, ATF1, WT1 and CHOP are fused to EWS generating distinct tumor phenotypes: clear cell sarcoma, desmoplastic small round cell tumor, and myxoid liposarcoma, respectively. We have cloned a novel gene located at 22q12 fused to EWS by a submicroscopic inversion of 22q in a small round cell sarcoma showing a translocation (t(1;22)(p36.1;q12). The gene, designated ZSG (Zinc finger Sarcoma Gene), is a putative Cys2-His2 zinc finger protein which contains a POZ transcriptional repressor-like domain at the N-terminus. The rearrangement involves intron 8 of EWS and exon 1 of ZSG creating a chimeric sequence containing the transactivation domain of EWS fused to zinc finger domain of ZSG. This product lacks the transcriptional repressor domain at the N-terminus of ZSG. A rearrangement of the second ZSG allele was also found in tumor cells. This is the first example of an intra-chromosomal rearrangement of chromosome 22, undetectable by cytogenetics, activating EWS in soft tissue sarcoma.

Biphenotypic sarcoma with characteristics of both a Ewing sarcoma and a desmoplastic small round cell tumor

BACKGROUND

The EWS gene, a transcription factor of unknown function, is involved in chromosomal translocations associated with a wide variety of tumors, particularly small round blue cell tumors such as Ewing sarcoma. It has previously been reported that desmoplastic small round blue cell tumor (DSRBCT) frequently has an associated t(11;22) abnormality resulting from fusion of the EWS and WT-1 genes.

PROCEDURE

We report a case of a small round blue cell tumor with characteristics of both Ewing sarcoma and DSRBCT with a t(11;22) translocation leading to fusion of the EWS and FLI1genes.

RESULTS

The translocation point and fusion products were confirmed by polymerase chain reaction amplification and restriction fragment mapping of the products.

CONCLUSIONS

The biphenotypic nature of this case and the apparent promiscuity of the EWS gene in tumor-associated translocations coupled with other reports of biphenotypic childhood sarcomas has potential implications for the relationship between small round blue cell tumors and the mechanism of EWS/FLI1 oncogenesis.

Immunohistochemical expression of WT1 by desmoplastic small round cell tumor: a comparative study with other small round cell tumors

Desmoplastic small round cell tumors (DSRCTs) present a reciprocal chromosomal translocation, t(11;22)(p13;q12), that results in fusion of Ewing's sarcoma and Wilms' tumor (WT1) genes. The authors evaluated 15 DSRCTs and 71 other tumors often considered in the differential diagnosis for immunoreactivity using a polyclonal antibody directed against the WT1 part of the chimeric protein resulting from this translocation. WT1 immunostaining was performed on paraffin material using the WT(C-19) antibody after heat-antigen retrieval. All the DSRCTs (15 of 15, 100%) demonstrated strong WT1 nuclear immunoreactivity. Ten of 14 nephroblastomas (71%) disclosed WT1-positive nuclei in accordance with the staining reported by others, and rare and focal nuclear positivity was detected in two of 17 rhabdomyosarcomas. WT1 immunoreactivity was not observed in Ewing's sarcoma/primitive neuroectodermal tumors (zero of 21, 0%), neuroblastomas (zero of 17, 0%), or rhabdoid tumors of the kidney (zero of two, 0%). In nephroblastoma, differential diagnosis with DSRCT was not difficult: Clinical and morphologic data are not similar for these two entities. The current study validates WT1 immunoreactivity as a useful marker to separate DSRCT from other small round cell tumors.

Cytokeratin immunoreactivity in Ewing's sarcoma: prevalence in 50 cases confirmed by molecular diagnostic studies

Ewing's sarcoma (ES) and primitive neuroectodermal tumor (PNET) are characterized by the presence of the specific t(11;22)(q24;q12) or variants thereof, producing diagnostic EWS fusion transcripts. Cytokeratin has been reported sporadically to be expressed in some cases of ES/PNET. However, its prevalence has not been assessed systematically in a series of cases with confirmatory molecular or cytogenetic evidence of a diagnostic translocation. We present in detail three index patients in whom strong cytokeratin immunoreactivity was a confounding factor in the diagnosis. To establish further the prevalence of cytokeratin immunoreactivity in a series of well-characterized ES/PNET, we then performed immunohistochemical studies with antibodies CAM5.2 and AE1/AE3 on 50 cases of ES/PNET diagnosed at Memorial Sloan-Kettering Cancer Center in which molecular evidence of a specific ES/PNET-associated translocation were available. Immunoreactivity to cytokeratin was present in 10 cases (20%), in five diffusely and five focally. There was no significant association between cytokeratin expression and the following parameters: patient age, sex, skeletal and extraskeletal primary site, and the type of EWS fusion transcript. Cytokeratin expression, a manifestation of epithelial differentiation, is present in as many as 20% of ES/PNET in either a diffuse or focal pattern.

CD99 positivity and EWS-FLI1 gene rearrangement identify a breast tumor in a 60-year-old patient with attributes of the Ewing family of neoplasms

Rearrangements of the EWS gene with ETS transcription factor genes as a result of chromosomal translocation and high expression levels of CD99MIC2 characterize the Ewing family of tumors (EFT). This group of rather undifferentiated neoplasms affects bone and soft tissue in children and young adults mostly between 5 and 30 years of age (median, 15 years). This study reports a case of a CD99MIC2 positive small round cell tumor in the breast of a 60-year-old woman in whom a t(11;22)(q24;q12) chromosomal aberration was identified by cytogenetic analysis. Reverse transcriptase (RT)-polymerase chain reaction (PCR) followed by sequence analysis revealed expression of a chimera transcript in which EWS exon 10 was fused to FLI1 exon 6. Previously, this gene fusion has been reported to occur in approximately 3% of EFT. The specific gene rearrangement of EWS intron 10 was confirmed on Southern blot of genomic DNA. This study further contributes to the growing list of unusual neoplasms in adults that carry genotypic and phenotypic traits of the EFT.

The Ewing family of tumors and the search for the Achilles' heel

The ideal cancer therapy would accomodate the specific biology of a tumor and be based upon understanding the mechanisms of malignancy. This vision has been the driving force in cancer research. However, the story of success in clinical cancer management is a story of empirie largely independent from progress in basic research. For the Ewing family of tumors (EFT) comprising Ewing's sarcoma and peripheral primitive neuroectodermal tumor, significant insights into the molecular basis have appeared recently. Some of last year's discoveries may have taken us closer to the identification of the Achilles' heel in this disease. The first clue has been obtained to the mechanism of chromosomal translocation, which constitutes a rate-limiting step in EFT pathogenesis. Also, researchers have progressed in understanding the control of EFT cell proliferation, differentiation, and death. A major role in these processes has been attributed to the EWS-ets gene rearrangement. Specific growth factor circuits appear to be involved in deregulated tumor cell growth. By analogy to heterologous cellular systems, it is possible to postulate an important functional role for CD99(MIC2) as it contributes to the malignant phenotype of EFT. In vitro, as well as the first in vivo, experimental evidence suggests that tumor cell expansion and spread can be counteracted by breaking these physiological pathways. Still, we are far from a tailored biological therapy of EFT. Before this goal may be achieved, we must seek further improvements and diversification of today's standard and intensified treatment regimens.

How shall we apply the new biology to diagnostics in surgical pathology?

Molecular technology plays an ever-increasing role in academic pathology and frequent claims are made that these technical developments will revolutionize diagnostic histopathology. In reviewing the role and potential utility of molecular genetics in the clinical practice of tumour pathology, it is evident that claims have outweighed facts, at least to date, and while molecular data have helped to clarify specific small areas of tumour classification and have facilitated the diagnosis of certain relatively rare tumours (especially on limited tissue), the overall impact on cancer management has been small. In particular, molecular markers of prognosis or tumour response have yet to impact substantially on the role of conventional light microscopic examination. We believe that these shortcomings have more to do with the generally different goals of basic medical science and clinical practice. In order to optimize the benefit to patients of modern molecular pathology, these techniques need to be rigorously appraised in the clinical setting and properly analysed in terms of cost-benefit. This requires close collaboration between the basic research community and histopathologists. Suggestions that 'H&E' pathology will be superceded in the near future are both premature and unrealistic.

Desmoplastic small round cell tumor: II: an ultrastructural and immunohistochemical study with emphasis on new immunohistochemical markers

In order to investigate the histogenesis and facilitate the diagnosis of desmoplastic small round cell tumor (DSRCT), 39 cases were studied by immunohistochemical methods using a large battery of antibodies directed against a wide variety of epithelial, mesenchymal, and neural-associated proteins. Sixteen of these tumors were also studied by electron microscopy. Thirty-seven of 39 cases reacted for cytokeratin using a "cocktail" of 3 monoclonal antibodies (CAM 5.2/AE1/AE3), 39/39 for desmin, 24/25 for epithelial membrane antigen, 22/27 for vimentin, 18/25 for neuron-specific enolase, 10/15 for CD57 (Leu-7), 3/19 for synaptophysin, 1/22 for chromogranin, 3/19 for muscle-specific actin, 3/16 for alpha-smooth-muscle actin, 11/16 for CD15 (Leu-M1), 5/12 for CA-125, 6/17 for CD99, 9/10 for MOC-31, 2/6 for NB84, 5/7 for Ber-EP4, and 8/9 for the Wilms tumor (WT1) protein. No staining was obtained in any of the cases tested for cytokeratin 5/6 or 20, neurofilament proteins, glial fibrillary acidic protein, peripherin, CA19-9, thrombomodulin, alphafetoprotein, carcinoembryonic antigen, TAG-72 (B72.3), placental alkaline phosphatase, S-100 protein, HMB-45, myoglobin, or for the two myogenic regulatory proteins myogenin and MyoD1. A frequent ultrastructural finding was the presence of juxtanuclear aggregates of intermediate filaments, but microfilaments with densities or Z-band-like material suggestive of either smooth or skeletal muscle differentiation were not seen in any case. Dendritic-like processes containing microtubules and dense core granules were seen in four tumors and all of these tumors reacted for at least one of the neural markers investigated. Although ultrastructural and immunohistochemical studies confirmed previous observations that DSRCTs present epithelial, mesenchymal, and neural phenotypes, a great variation was found in the frequency of expression of the different markers used to demonstrate each line of cell differentiation. The absence of expression of cytokeratin 5/6 and thrombomodulin together with positive staining for CD15, MOC-31, and Ber-EP4 argues against the possible mesothelial origin that has been suggested for this tumor. Additionally since none of the tumors reacted for myogenin or MyoD1, desmin expression in DSRCT cannot be regarded as evidence of skeletal muscle differentiation. Although the histogenesis of DSRCT remains unknown, it is believed that this tumor originates from a progenitor cell with potential for multiphenotypic differentiation.

Intraabdominal desmoplastic small round cell tumor with EWS/ERG fusion transcript

This report describes an intraabdominal small cell tumor in a 37-year-old woman, with clinical, topographic, and morphologic features highly suggestive of the desmoplastic small round cell tumor. Immunohistochemical analysis revealed a polyphenotypic profile consistent with this tumor--positivity for keratin, epithelial membrane antigen, neuron-specific enolase, vimentin, and desmin--but, in addition, a strong membranous immunoreactivity for CD99 (MIC2 protein). Reverse transcription polymerase chain reaction revealed a EWS/ERG fusion transcript characteristic of the Ewing's sarcoma/peripheral primitive neuroectodermal tumor group of tumors, rather than the EWS/WT1 chimeric transcript typical of the desmoplastic small round cell tumor. This is the third report of a hybrid tumor with features of the desmoplastic small round cell tumor and Ewing's sarcoma/peripheral primitive neuroectodermal tumor, and the first one with the EWS/ERG fusion gene. Our case shows the existence of some overlap between these two groups of tumors, which are considered to be histogenetically different, and the need for further studies of molecular characterization of small cell tumors, especially in those with atypical morphologic or immunohistochemical features.

Molecular features in a biphenotypic small cell sarcoma with neuroectodermal and muscle differentiation

We report a case of a 13-year-old girl with soft tissue sarcoma of the hand, which showed muscle and neuroectodermal immunophenotypes. Molecular studies were performed on RNA collected from fine-needle aspiration (FNA) cytology and peripheral blood samples by nested reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blot analysis. This biphenotypic tumor showed simultaneous expression of EWS-FLI1 and PAX3-FKHR transcripts, specific of Ewing family tumors and alveolar rhabdomyosarcoma, respectively. Although childhood sarcomas with simultaneous muscle and neural differentiation have been described to have EWS-FLI1 transcripts, there are no reports of tumors with both transcripts. Cytological specimens are a good source of RNA for molecular studies.