Updates on the cytogenetics and molecular genetics of bone and soft tissue tumors: congenital (infantile) fibrosarcoma and mesoblastic nephroma

From oncogenes to tumor suppressors: The dual role of ncRNAs in fibrosarcoma

Fibrosarcoma is a challenging cancer originating from fibrous tissues, marked by aggressive growth and limited treatment options. The discovery of non-coding RNAs (ncRNAs), including long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and small interfering RNAs (siRNAs), has opened new pathways for understanding and treating this malignancy. These ncRNAs play crucial roles in gene regulation, cellular processes, and the tumor microenvironment. This review aims to explore the impact of ncRNAs on fibrosarcoma's pathogenesis, progression, and resistance to treatment, focusing on their mechanistic roles and therapeutic potential. A comprehensive review of literature from databases like PubMed and Google Scholar was conducted, focusing on the dysregulation of ncRNAs in fibrosarcoma, their contribution to tumor growth, metastasis, drug resistance, and their cellular pathway interactions. NcRNAs significantly influence fibrosarcoma, affecting cell proliferation, apoptosis, invasion, and angiogenesis. Their function as oncogenes or tumor suppressors makes them promising biomarkers and therapeutic targets. Understanding their interaction with the tumor microenvironment is essential for developing more effective treatments for fibrosarcoma. Targeting ncRNAs emerges as a promising strategy for fibrosarcoma therapy, offering hope to overcome the shortcomings of existing treatments. Further investigation is needed to clarify specific ncRNAs' roles in fibrosarcoma and to develop ncRNA-based therapies, highlighting the significance of ncRNAs in improving patient outcomes in this challenging cancer.

EGFR internal tandem duplications in fusion-negative congenital and neonatal spindle cell tumors

Next-generation sequencing (NGS) assays can sensitively detect somatic variation, and increasingly can enable the identification of complex structural rearrangements. A subset of infantile spindle cell sarcomas, particularly congenital mesoblastic nephromas with classic or mixed histology, have structural rearrangement in the form of internal tandem duplications (ITD) involving EGFR. We performed prospective analysis to identify EGFR ITD through clinical or research studies, as well as retrospective analysis to quantify the frequency of EGFR ITD in pediatric sarcomas. Within our institution, three tumors with EGFR ITD were prospectively identified, all occurring in patients less than 1 year of age at diagnosis, including two renal tumors and one mediastinal soft tissue tumor. These three cases exhibited both cellular and mixed cellular and classic histology. All patients had no evidence of disease progression off therapy, despite incomplete resection. To extend our analysis and quantify the frequency of EGFR ITD in pediatric sarcomas, we retrospectively analyzed a cohort of tumors (n = 90) that were previously negative for clinical RT-PCR-based fusion testing. We identified EGFR ITD in three analyzed cases, all in patients less than 1 year of age (n = 18; 3/18, 17%). Here we expand the spectrum of tumors with EGFR ITD to congenital soft tissue tumors and report an unusual example of an EGFR ITD in a tumor with cellular congenital mesoblastic nephroma histology. We also highlight the importance of appropriate test selection and bioinformatic analysis for identification of this genomic alteration that is unexpectedly common in congenital and infantile spindle cell tumors.

Unusual Case of Concurrent Retroperitoneal Congenital Infantile Fibrosarcoma and Cellular Type Congenital Mesoblastic Nephroma

BACKGROUND

Although congenital infantile fibrosarcoma (cIFS) is a rare soft tissue sarcoma among children, it constitutes one of the most common soft tissue sarcomas during the first year of life. Congenital mesoblastic nephroma (CMN) is the most common benign renal tumor usually developing during the first 3 months of life. cIFS and cellular type CMN (cCMN) share not only similar histopathologic features but identical molecular genetic abnormality including the ETV6/NTRK3 fusion gene. Here, we report an unusual case of cIFS occurring with cCMN.

CASE PRESENTATION

An 18-month-old girl presented with a 1-month history of abdominal distension and a few days' history of a palpable abdominal mass. A large heterogenous mass sized 9.0×11.2×11.6 cm on the right side of the abdomen and an isolated heterogenous lesion sized 4×4.5 cm within the right kidney were noted from the imaging study. Pathologic findings were consistent with cIFS and cCMN of the right kidney. In addition, both pathologic specimens contained the ETV6/NTRK3 fusion gene.

CONCLUSION

Although cIFS and cCMN share similar histopathologic features and molecular genetic abnormality, simultaneous occurrence of these 2 types of tumor is exceedingly rare. To our knowledge, this is the first unusual case report of concurrent cIFS and cCMN.

Infantile fibrosarcoma-like tumor driven by novel RBPMS-MET fusion consolidated with cabozantinib

Infantile fibrosarcoma (IFS) is nearly universally driven by gene fusions involving the NTRK family. ETV6-NTRK3 fusions account for ∼85% of alterations; the remainder are attributed to NTRK-variant fusions. Rarely, other genomic aberrations have been described in association with tumors identified as IFS or IFS-like. We describe the utility of genomic characterization of an IFS-like tumor. We also describe the successful treatment combination of VAC (vincristine, actinomycin, cyclophosphamide) with tyrosine kinase inhibitor (TKI) maintenance in this entity. This patient presented at birth with a right facial mass, enlarging at 1 mo to 4.9 × 4.5 × 6.3 cm. Biopsy demonstrated hypercellular fascicles of spindle cells with patchy positivity for smooth muscle actin (SMA) and negativity for S100, desmin, myogenin, and MyoD1. Targeted RNA sequencing identified a novel RBPMS-MET fusion with confirmed absence of ETV6-NTRK3, and the patient was diagnosed with an IFS-like tumor. A positron emission tomography (PET) scan was negative for metastatic disease. VAC was given for a duration of 10 mo. Resection at 13 mo of age demonstrated positive margins. Cabozantinib, a MET-targeting TKI, was initiated. The patient tolerated cabozantinib well and has no evidence of disease at 24 mo of age. We describe a novel RBPMS-MET driver fusion in association with a locally aggressive IFS-like tumor. MET functions as an oncogene and, when associated with the RNA binding protein RBPMS, forms an in-frame fusion product that retains the MET kinase domain. This fusion is associated with aberrant cell signaling pathway expression and subsequent malignancy. We describe treatment with cabozantinib in a patient with an IFS-like neoplasm.

The impact of local control in the treatment of children with advanced infantile and adult-type fibrosarcoma: Experience of the cooperative weichteilsarkom studiengruppe (CWS)

BACKGROUND AND OBJECTIVES

This study aims at examining the potential survival benefits of primary versus secondary surgery of children diagnosed with advanced infantile (iFS) and adult-type fibrosarcoma (aFS).

METHODS

Treatment and outcome of 89 children with FS treated within prospective Cooperative Studiengruppe (CWS) trials (1981-2016) were analyzed retrospectively.

RESULTS

Localized disease (LD) was diagnosed in 87 patients: 64/66 patients with iFS (≤2 years) and 23 with aFS (>2 ≤ 18 years). Two patients (iFS) had metastatic disease. Resection was the mainstay of therapy of patients with LD resulting in microscopically complete (R0, IRS group I) (n = 29/87, 33%), microscopically incomplete (R1, IRS group II) (n = 17/87, 20%) and macroscopically incomplete (R2, IRS group III) (n = 41/87, 47%). Advanced LD (IRS group III) was present in 32/64 (50%) patients with iFS and in 9/23 (39%) with aFS. Chemotherapy was added predominantly in patients with advanced disease and an assessable objective response to CHT was seen in 71% iFS and 75% aFS. The 5-year event-free survival (EFS) of patients with iFS and aFS was 81% (±10, 95% CI) and 70% (±19, 95% CI) (p = 0.24); the 5-year overall survival (OS) was 98% (±3, 95% CI) and 82% (±16, 95% CI) (p = 0.02). Primary resection was no prognostic factor. Secondary R0/ R1 resection in patients with advanced disease improved 5-year EFS and OS in aFS (p = 0.002 and p = 0.000) but not in infants.

CONCLUSIONS

Secondary resection improves outcome in advanced aFS but not in infants. Mutilating surgery in infants should be avoided.

TYPE OF STUDY AND LEVEL OF EVIDENCE

Treatment study: patients were enrolled in five prospective studies and one registry, prognosis study: retrospective study.

LEVEL OF EVIDENCE

II/ III.

MINI-ABSTRACT

Fibrosarcoma is a very rare malignant tumor. Little is known about differences of local treatment of advanced infantile and adult-type. Data of 89 patients registered in five prospective trials and one registry of the Cooperative Weichteilsarkom Studiengruppe (CWS) (1981-2016) were analyzed.

Recurrent EGFR alterations in NTRK3 fusion negative congenital mesoblastic nephroma

Objectives

To identify oncogenic driver mutations in congenital mesoblastic nephroma (CMN) cases lacking ETV6-NTRK3 fusion and discuss their diagnostic value.

Design

The institutional pathology database was queried for cases with a morphologic diagnosis of CMN. Cases positive for ETV6 rearrangement or with unavailable blocks were excluded. Four cases met the inclusion criteria and were sequenced by next-generation sequencing. Three additional cases were contributed by our collaborators.

Results

Three of four internal cases harbor an EGFR kinase domain duplication (KDD), which is known to be oncogenic yet exceedingly rare in other histologies. All three outside cases are positive for EGFR alterations, including KDD in two and a splicing site mutation in one. The splicing site mutation is predicted to be EGFR activating. One of the outside cases was a retroperitoneal mass without a clear site of origin. A diagnosis of CMN is suggested based on exclusion of differential diagnoses by expert consultation and detection of EGFR KDD.

Conclusions

EGFR activation, predominantly via EGFR KDD, is a common recurrent genetic alteration in CMN lacking NTRK3 fusions. CMN can be molecularly classified into NTRK3 fusion type, EGFR activation type and others.

Diagnostic Value of TLE1 in Synovial Sarcoma: A Systematic Review and Meta-Analysis

Background

Synovial sarcoma can present morphologically in multiple forms, including biphasic and monophasic subtypes. As a result, the histological diagnosis can sometimes be challenging. Transducin-Like Enhancer 1 (TLE1) is a transcriptional corepressor that normally is involved in embryogenesis and hematopoiesis but is also expressed in certain tumors. This systematic review examines the potential role of TLE1 as a diagnostic biomarker for the synovial sarcoma. Materials and Methods. A literature review and meta-analysis were conducted using the electronic databases Pubmed, the Cochrane Library, and Google Scholar. Thirteen studies met our eligibility criteria and were selected for in-depth analysis.

Results

The mean sensitivity and specificity of TLE1 in detecting synovial sarcoma were 94% (95% CI 91%-97%) and 81% (95% CI 72%-91%), respectively, when all studies were aggregated together. The mean positive predictive value (PPV) of TLE1 was 75% (95% CI 62%-87%), whereas the negative predictive value (NPV) was 96% (95% CI 93%-98%).

Conclusion

TLE1 is a sensitive and specific marker for synovial sarcoma that can aid in its diagnosis. Due to its involvement in several relevant signaling pathways, TLE1 might have direct relevance to the pathophysiology of the disease.

Congenital mesoblastic nephroma: a single-centre series

BACKGROUND

Congenital mesoblastic nephroma is a rare disease. Treatment is surgical in the first instance. Chemotherapy has traditionally been thought not to have a role. Recent literature suggests a 50% mortality rate for recurrent/metastatic disease.

MATERIALS AND METHODS

This study is a retrospective case review of prospectively collected data. Demographics, histopathology, treatment, outcomes and follow up were reviewed.

RESULTS

Nine patients, 6 male and 3 female, were included. The median age at presentation was one month (range 0-7 months); follow-up was for a median of 21.5 months (range 16-79 months). Two patients had mixed and classical subtypes and the other five had the cellular subtype. Surgery was completed by an open procedure in eight patients and laparoscopically in one. There were three recurrences; two were local and one was pulmonary. Recurrences were treated with a combination of chemotherapy, radiotherapy and surgery. One patient with recurrent disease died from acute-on-chronic respiratory failure secondary to lung irradiation but was disease free. The other eight are disease free, alive and well with no sequelae at latest follow-up.

CONCLUSIONS

Surgery remains the mainstay of management with chemo- and radiotherapy reserved for unresectable tumours or adjuvant management of recurrent disease. Specimen-positive margins are not an indication for instituting chemotherapy. The tyrosine kinase pathway seems to be a potential target for future chemotherapeutic agents although it is too early to assess how that will impact on the management of congenital mesoblastic nephroma.

Metanephric stromal tumor: An unusual presentation of a rare paediatric renal neoplasm

A 2-year-old boy with prenatal diagnosis of a malformation uropathy was referred to paediatric surgery department. On systemic examination, there were no palpable masses. An ultrasonography of abdomen with color Doppler, a renal artery angiographic and scintigraphy revealed a preostial aneurysm at the left renal artery. The patient had a left nephrectomy. Grossly, the specimen measured 75 mm × mm 50 × 20 mm with renal artery aneurysm measuring 30 mm × 35 mm. On cut section, the renal parenchyma contained a whitish tumor that measured 35 mm × 10 mm. Histopathologically, this tumor was diagnosed as metanephric stromal tumor.

Infantile NTRK-associated Mesenchymal Tumors

Pediatric fibroblastic/myofibroblastic lesions are a relatively common group of tumors with varying morphologies, for which the molecular mechanisms are becoming increasingly well characterized. Congenital infantile fibrosarcoma (CIFS), perhaps the most well studied of these lesions is characterized by a recurrent ETV6-NTRK3 gene fusion. However, a notable subset of locally aggressive congenital/infantile soft tissue lesions with similar morphologic features to CIFS, have not to-date, shown evidence of any canonical molecular aberration. We describe 6 patients with mesenchymal tumors composed of infiltrative fibroblastic/myofibroblastic tumor cells and showing a morphologic spectrum of features much analogous to that previously described in CIFS but without ETV6 fusion transcripts. These tumors lacked a uniform immunoprofile, but showed variable expression of CD34, S100, smooth muscle actin, and CD30. All patients first developed a mass in infancy (≤2 months of age). Using next-generation DNA sequencing, TMP3-NTRK1 fusions were identified in 4 cases, an LMNA-NTRK1 fusion in one case, and a variant EML4-NTRK3 fusion in one case. Similar to infantile fibrosarcoma, these tumors were locally aggressive (with local recurrences if incompletely excised) and rarely metastasized (lung metastases in one patient). Proper identification of these tumors including investigation for NTRK family gene rearrangements is essential for diagnostic accuracy, as well as for clinical management decisions. Given the morbidity associated with radical resection of large soft tissue tumors, children with unresectable, recurrent, and/or metastatic disease may benefit from treatment with NTRK targeted therapies.

Recurrent and metastatic congenital mesoblastic nephroma: where does the evidence stand?

PURPOSE

Fifty years ago, Bolande described Congenital Mesoblastic Nephroma (CMN) as a benign lesion. Unexpected aggressive clinical behaviors prompted a sub-classification based on histology. Recent molecular genetic evidence has identified the aggressive cellular variant to be the renal manifestation of congenital infantile fibrosarcoma. We submit a reappraisal and analysis of the available literature on recurrent and metastatic CMN.

METHODS

An electronic search of PubMed, MEDLINE, EMBASE, and Scopus yielded 38 children with local recurrence and/or metastases.

RESULTS

Of the 38 children with local recurrence and/or metastasis, 59% were girls. Median time to recurrence was 6 months (range 1-12 months). The commonest sites of metastases were the lung (39%) and liver (29%). Fifty percent of these children died of disease. The outcome of additional chemotherapy (p = 0.5) did not differ from that of surgery alone. The choice of chemotherapy did not influence the outcome (p = 0.6).

CONCLUSIONS

Recurrence and metastasis in cellular CMN are much more common than described earlier and carry a high mortality. Children with cellular and mixed CMN require close clinical and radiological follow-up for a minimum of 12 months after primary surgery. Surgery is the mainstay of the treatment of recurrent and metastatic lesions. Neoadjuvant chemotherapy is recommended only if the lesion is inoperable. Targeted therapy may be an option in treatment of refractory cases.

Identification of SETD2-NF1 fusion gene in a pediatric spindle cell tumor with the chromosomal translocation t(3;17)(p21;q12)

Spindle cell tumors are clinically heterogeneous but morphologically similar neoplasms. The term refers to the tumor cells' long and slender microscopic appearance. Distinct subgroups of spindle cell tumors are characterized by chromosomal translocations and also fusion genes. Other spindle cell tumors exist that have not yet been found to have characteristic, let alone pathognomonic, genetic or pathogenetic features. Continuous examination of spindle cell tumors is likely to reveal other subgroups that may, in the future, be seen to correspond to meaningful clinical differences and may even be therapeutically decisive. We analyzed genetically a pediatric spindle cell tumor. Karyotyping showed the tumor cells to carry a t(3;17)(p21;q12) chromosomal translocation whereas RNA sequencing identified a SETD2-NF1 fusion gene caused by the translocation. RT-PCR together with Sanger sequencing verified the presence of the above-mentioned fusion transcript. Interphase FISH analysis confirmed the existence of the chimeric gene and showed that there was no reciprocal fusion. The fusion transcript codes for a protein in which the last 114 amino acids of SETD2, i.e., the entire Set2 Rpb1 interacting (SRI) domain of SETD2, are replaced by 30 amino acids encoded by the NF1 sequence. The result would be similar to that seen with truncating SETD2 mutations in leukemias. Absence of the SRI domain would result in inability to recruit SETD2 to its target gene locus through binding to the phosphor-C-terminal repeat domain of elongating RNA polymerase II and may affect H3K36 methylation. Alternatively, loss of one of two functional SETD2 alleles might be the crucial tumorigenic factor.

Pediatric genitourinary oncology

Tumors of the kidney, bladder, prostate, testis, and adrenal represent a large part of the adult urologic practice, but are relatively infrequent in children. The natural history and management of these tumors in the pediatric age is different from that of the adults. As result of the successful work of several clinical trial groups in recent decades, there has been a significant improvement in their cure rates. The aim of this article is to review their most significant clinical aspects, as well as to present an update in their management.

Clinical, histologic, and genetic features of mesothelioma in a 7-year-old child

Malignant mesothelioma (MM) is a highly aggressive malignancy that is extremely rare in children. This case report documents a 7-year-old male without previous asbestos exposure with peritoneal MM that initially responded to chemotherapy with cisplatin and gemcitabine but ultimately metastasized to his chest. He was diagnosed with MM based on histology, extensive immunohistochemical analyses, and an elevated serum CA-125 level. Cytogenetics and comparative genomic hybridization (CGH) analysis of his tumor identified a single extra copy number of chromosome 11 with few other changes noted.

Recurrent congenital fibrosarcoma with heart metastases

Congenital fibrosarcomas are malignant tumors that arise in soft tissues. In infants this unique tumor does not commonly metastasize, even though there may be local recurrences. We report here a boy who had congenital fibrosarcoma in his right foot, which was completely excised at the age of 3 days. Four months later, a solitary encapsulated metastasis emerged in thoracic chest wall, which was operated. During adjuvant chemotherapy he developed histologically confirmed fibrosarcoma metastases in the heart. After extended treatment with cyclophosphamide/topotecan and gemcitabine/docetaxel, the heart tumors disappeared and he has been in complete remission for 3 years.

Fibroblastic and myofibroblastic tumors in children and adolescents

Fibroblastic and myofibroblastic tumors in children and adolescents are a relatively common group of soft tissue proliferations that range from reactive to hamartomatous to neoplastic, with a full spectrum of benign, intermediate, and malignant neoplasms. These lesions are diagnostically challenging because of morphologic and immunohistochemical overlap, despite significant clinical, genetic, and prognostic differences. The fibromatoses are a major subgroup, and all types of fibromatoses can occur in the 1st 2 decades of life. Intermediate and malignant fibroblastic-myofibroblastic tumors are an important group that includes variants of fibrosarcoma and other tumors with recurrent cytogenetic or molecular genetic abnormalities and low metastatic potential. Pathologic examination is enhanced by adjunct techniques, such as immunohistochemistry, cytogenetics, and molecular genetics, although morphology provides the ultimate criteria for a specific diagnosis. This article reviews the clinicopathologic features of fibroblastic and myofibroblastic tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents, the use of diagnostic adjuncts, and differential diagnoses.

[Fibrosarcoma in children and adolescents: different entities for the same name]

Fibrosarcomas (FS) are rare malignant tumors in pediatrics, classified in the heterogeneous non-rhabdomyosarcomas group of malignant mesenchymal tumors. Infantile FS are found typically in children less than 2 years of age, and include congenital FS usually occurring in infants in the first 3 months of life. Histological diagnosis can be difficult; and confirmed with detection by molecular biology of the ETV6-NTRK3 fusion protein. FS is most often a localized disease at diagnosis, with involvement of an extremity. The management of these patients must be multidisciplinary, to define the different phases of treatment and avoid mutilating surgery. Cellular or atypical mesoblastic nephroma (MN) is a subtype of malignant pediatric renal tumors, most often present in children of less than 3 months. Histopathological characteristics of the cellular MN are very close to the congenital FS due to a fusion transcript common to both diseases. Treatment schedule is defined by initial local stage of the disease. FS called "adult-type" found exceptionally in childhood occur most often after 10 years old. Adult FS differ from infantile FS in their clinical presentation because of a strong local aggressiveness and problematic appearance of metastasis in 50% of cases, sometimes late. These three diseases present therefore histological similarities. Both have a common name but different clinical presentation and outcome: infantile FS and adult FS. Two have different names and initial location but similar histology, chromosomal rearrangement, sensitivity to chemotherapy and outcome: the congenital FS and cellular mesoblatic nephroma. Authors present a review of the literature of these entities.

p53-Independent, normal stem cell sparing epigenetic differentiation therapy for myeloid and other malignancies

Cytotoxic chemotherapy for acute myeloid leukemia (AML) usually produces only temporary remissions, at the cost of significant toxicity and risk for death. One fundamental reason for treatment failure is that it is designed to activate apoptosis genes (eg, TP53) that may be unavailable because of mutation or deletion. Unlike deletion of apoptosis genes, genes that mediate cell cycle exit by differentiation are present in myelodysplastic syndrome (MDS) and AML cells but are epigenetically repressed: MDS/AML cells express high levels of key lineage-specifying transcription factors. Mutations in these transcription factors (eg, CEBPA) or their cofactors (eg., RUNX1) affect transactivation function and produce epigenetic repression of late-differentiation genes that antagonize MYC. Importantly, this aberrant epigenetic repression can be redressed clinically by depleting DNA methyltransferase 1 (DNMT1, a central component of the epigenetic network that mediates transcription repression) using the deoxycytidine analogue decitabine at non-cytotoxic concentrations. The DNMT1 depletion is sufficient to trigger upregulation of late-differentiation genes and irreversible cell cycle exit by p53-independent differentiation mechanisms. Fortuitously, the same treatment maintains or increases self-renewal of normal hematopoietic stem cells, which do not express high levels of lineage-specifying transcription factors. The biological rationale for this approach to therapy appears to apply to cancers other than MDS/AML also. Decitabine or 5-azacytidine dose and schedule can be rationalized to emphasize this mechanism of action, as an alternative or complement to conventional apoptosis-based oncotherapy.

Myofibroma, Myopericytoma, Myoepithelioma, and Myofibroblastoma of Skin and Soft Tissue

The authors address a group of loosely associated, characteristically benign soft tissue neoplasms that exhibit partial myoid differentiation. The entities share similarities in morphology and in nomenclature that have historically created confusion. The authors attempt to clarify the distinct architectural patterns and the corresponding immunophenotypic and ultrastructural features that distinguish myofibroma, myopericytoma, myoepithelioma, and myofibroblastoma.

Unusual presentation of congenital infantile fibrosarcoma in seven infants with molecular-genetic analysis

Congenital infantile fibrosarcoma (CIFS) is a rare mesenchymal tumor that primarily presents in the soft tissue of the distal extremities and occasionally in unusual locations such as the lung and retroperitoneum. Herein, we report seven cases of unusual presentations of CIFS. These cases include three in the lungs, one in the retroperitoneum with cord compression, one in the posterior trunk, one in the heart, and one infratemporal involving the sphenoid bone. All tumors demonstrated CIFS's characteristic t(12;15)(p13;q25) and associated ETV6-NTRK3 gene fusion. One of the three lung cases was previously reported as primary bronchopulmonary fibrosarcoma (PBPF), but molecular analysis of the paraffin embedded tissue revealed the ETV6-NTRK3 gene fusion consistent with CIFS. We show that CIFS may occur in unusual sites including visceral locations, and we propose that neoplasms displaying the ETV6-NTRK3 gene fusion represent the visceral components of CIFS.

Pleomorphic Sarcoma as a Mimicker of Sarcomatous Carcinoma

The fourth case of a poorly differentiated sarcoma histologically mimicking a sarcomatous carcinoma is reported. The tumor was focally weakly positive for keratin, moderately focally positive for epithelial membrane antigen, muscle-specific actin, smooth muscle actin, and calponin, and strongly diffusely positive for vimentin. The neoplastic cells were closely apposed, often without intervening intercellular matrix; the cell membranes were straight and contained desmosome-like junctions. The cytoplasm contained a moderate number of mitochondria, rough endoplasmic reticulum, ribosomes, and many vesicles. The karyotype was complex and many chromosomal rearrangements were present. The diagnostic term carcinomatoid sarcoma is proposed for these interesting, insufficiently studies, tumors.

The Spectrum of Pediatric Fibroblastic and Myofibroblastic Tumors

Fibroblastic and myofibroblastic tumors in neonates, infants, and children provide a diagnostic dilemma in surgical pathology due to their relative rarity and similarity in appearances. These tumors may be congenital or occur early during the first years of life or later during the first and second decades of life. The morphologic, immunocytochemical, ultrastructural, cytogenetic, and molecular features of the more "common" pediatric fibroblastic and myofibroblastic tumors are reviewed. In addition, the importance of a multimodal approach to tumor diagnosis is emphasized, with correlation with treatment and outcome differences among these unique fibroblastic and myofibroblastic tumors. The importance of providing an accurate diagnosis with pediatric fibroblastic and myofibroblastic tumors cannot be overstated, because treatment, prognosis, follow-up, and outcome are based on the initial assessment of these fascinating, but oftentimes, perplexing tumors.

Infantile fibrosarcoma: clinical and histologic responses to cytotoxic chemotherapy

BACKGROUND

Infantile fibrosarcoma (IF) is a rare soft tissue sarcoma that presents either at birth or in the first year of life. Complete surgical resection is usually curative but chemotherapy may shrink the tumor to facilitate complete resection. This report describes the histologic changes and outcomes in four patients with IF treated with chemotherapy and surgical resection.

PROCEDURE

A retrospective review was performed of patients treated between 2000 and 2007.

RESULTS

All four patients are alive with excellent functional outcomes. The patients were diagnosed from birth up to 7 months of age; three had lower extremity tumors and one had a neck tumor. All patients received vincristine, cyclophosphamide, and actinomycin; one patient also received ifosfamide and etoposide after tumor progression. One tumor, arising from the neck, had rapid shrinkage. Two lower extremity tumors had only modest changes in dimensions but upon resection, the tumor bed contained fibrous tissue with exaggerated small caliber vessels. The fourth infant developed metastatic lesions in the central nervous system, orbits, lungs, and kidney after complete removal of the primary tumor. The metastatic lesions responded to chemotherapy and have remained stable for over 3 years.

CONCLUSIONS

IF is a chemosensitive tumor. In patients where a clinical response is not apparent, cytoreduction of the tumor and replacement with fibrotic and fibrovascular tissue may facilitate gross-total resection. The chemotherapy-responsiveness of this tumor may abrogate unfavorable features such as metastatic or residual tumor.

Pediatric Renal Neoplasms

Renal tumors in childhood consist of a diverse group of tumors ranging from the most common Wilms' tumor, to the uncommon and often fatal rhabdoid tumor. Diagnosis is based on morphologic features and aided by ancillary techniques such as immunohistochemistry and cytogenetics. Molecular techniques have helped identify a group of pediatric renal cell carcinomas that have specific translocations, called translocation-associated carcinomas. Differential diagnosis of the various tumors is discussed. Pathogenesis and nephroblastomatosis, the precursor lesions of Wilms tumor, also are discussed briefly, as are the handling of these tumor specimens and prognostic factors.

Congenital fibrosarcoma with a novel complex 3-way translocation t(12;15;19) and unusual histologic features

Congenital mesenchymal tumors are diagnostically challenging as they are rare and may feature overlapping patterns between several benign, low-grade, and tumors of intermediate malignancy, including myofibromatosis, myofibroma/hemangiopericytoma, congenital fibrosarcoma, and inflammatory myofibroblastic tumor. Their immunophenotype is either silent or minimally expressive, and their ultrastructural features are generically consistent with "fibroblastic/myofibroblastic" differentiation. Cytogenetic analysis allows refined diagnoses, improved classifications, and bettering of our therapeutic armamentarium. However, genotype/phenotype correlations continue rendering novel findings that must be examined for their potential value in diagnosis and treatment. We describe a retroperitoneal congenital fibrosarcoma with an unusually bland histopathology and novel 3-way t(12;15;19) translocation involving chromosome bands 12p13.2, 15q25.3, and 19p13.1, associated with trisomies 8, 11, and 20. Fluorescence in situ hybridization showed one fusion signal in the normal chromosome 12p13.2 and break-apart 3'ETV6 and 5'ETV6 signals in the rearranged 12p13.2 and 15q25.3, respectively. The importance of molecular diagnosis and genotype-phenotype correlations is emphasized.

The spectrum of pediatric tumors in infancy, childhood, and adolescence: a comprehensive review with emphasis on special techniques in diagnosis

The spectrum of pediatric tumors varies considerably, from those derived from blastemal cells in various organ systems to proliferations of soft tissue supporting cells to hamartomatous processes that mimic malignant tumors. Small round cell tumors are often undifferentiated or poorly differentiated, making it difficult sometimes to provide a definitive diagnosis. Both benign and malignant tumors require a coordinated method for diagnosis, and need a comprehensive evaluation to provide the most appropriate diagnosis for designing therapy and predicting prognosis. Pediatric tumors require the integration of routine histopathologic examination with histochemical, immunocytochemical, ultrastructural, cytogenetic, and diagnostic molecular pathology techniques. This review provides updated guidelines with respect to the application of these special techniques in this rapidly evolving diagnostic arena.

[Prenatal diagnosis of congenital mesoblastic nephroma. A case report]

Antenatal ultrasounds allow the detection of renal tumors, especially renal mesoblastic nephromas, but only the pathological analysis of the surgical specimen can confirm this diagnosis postnatally.

OBSERVATION

We report the prenatal discovery of a mesoblastic nephroma because of premature labour. Postnatal early surgery was decided because of possible complications in this premature infant. Histology revealed mesoblastic nephroma.

COMMENTS

We point out the diagnostic elements of congenital mesoblastic nephroma, especially in what is related to arterial hypertension and hypercalcemia, histology and cytogenetics.

KIT expression in fetal, normal adult, and neoplastic renal tissues

BACKGROUND

KIT is a transmembrane tyrosine kinase receptor, expressed in high amounts in various normal cells. In addition, c-kit mutation or activation is a major pathogenetic event in certain tumours (such as gastrointestinal stromal tumours). There are only limited data in the literature on the expression of KIT in normal and neoplastic renal tissues.

AIMS

To investigate KIT expression in normal and neoplastic renal tissues.

METHODS

KIT expression was evaluated by means of immunohistochemistry in paraffin wax embedded sections from 67 tissue samples.

RESULTS

Eight of eight fetal kidneys, and 10 of 10 normal adult kidneys revealed cytoplasmic staining of renal tubules. The three cases of renal dysplasia studied expressed KIT in their normal and aberrant tubules. Two of 13 conventional renal cell carcinomas (RCCs), two of seven papillary type RCCs, four of seven chromophobe type RCCs, none of six nephroblastomas, seven of seven oncocytomas, two of two mesoblastic nephromas, and two of four angiomyolipomas were positive.

CONCLUSION

KIT is expressed in normal fetal and adult renal tubules, and in a subset of renal tumours. The expression of KIT in these renal tumours may prove to have diagnostic relevance and/or therapeutic implications.

Mechanisms of sarcoma development

Sarcomas are a rare and diverse group of tumours that are derived from connective tissues, including bone, muscle and cartilage. Although there are instances of hereditary predisposition to sarcomas, the overwhelming majority of such tumours are sporadic. In the past decade, we have gained much insight into the genetic abnormalities that seem to underlie the pathogenesis of these tumours. This information has already led to new classification of many sarcomas, as well as to successful therapies that are targeted at specific genetic abnormalities. It is likely that this approach will lead to continued refinements in classification and treatment of these tumours.

Genetics of dermatofibrosarcoma protuberans family of tumors: from ring chromosomes to tyrosine kinase inhibitor treatment

Dermatofibrosarcoma protuberans (DP) is a rare, slow-growing, infiltrating dermal neoplasm of intermediate malignancy, made up of spindle-shaped tumor cells often positive for CD34. The preferred treatment is wide surgical excision with pathologically negative margins. At the cytogenetic level, DP cells are characterized by either supernumerary ring chromosomes, which have been shown by using fluorescence in situ hybridization techniques to be derived from chromosome 22 and to contain low-level amplified sequences from 17q22-qter and 22q10-q13.1, or t(17;22), that are most often unbalanced. Both the rings and linear der(22) contain a specific fusion of COL1A1 with PDGFB. Similar to other tumors, the COL1A1-PDGFB fusion is occasionally cryptic, associated with complex chromosomal rearrangements. Although rings have been mainly observed in adults, translocations have been reported in all pediatric cases. DP is therefore a unique example of a tumor in which (i) the same molecular event occurs either on rings or linear translocation derivatives, (ii) the chromosomal abnormalities display an age-related pattern, and (iii) the presence of the specific fusion gene is associated with the gain of chromosomal segments, probably taking advantage of gene dosage effects. In all DP cases that underwent molecular investigations, the breakpoint localization in PDGFB was found to be remarkably constant, placing exon 2 under the control of the COL1A1 promoter. In contrast, the COL1A1 breakpoint was found to be variably located within the exons of the alpha-helical coding region (exons 6-49). No preferential COL1A1 breakpoint and no correlation between the breakpoint location and the age of the patient or any clinical or histological particularity have been described. The COL1A1-PDGFB fusion is detectable by multiplex RT-PCR with a combination of forward primers designed from a variety of COL1A1 exons and one reverse primer from PDGFB exon 2. Recent studies have determined the molecular identity of "classical" DP, giant cell fibroblastoma, Bednar tumor, adult superficial fibrosarcoma, and the granular cell variant of DP. In approximately 8% of DP cases, the COL1A1-PDGFB fusion is not found, suggesting that genes other than COL1A1 or PDGFB might be involved in a subset of cases. It has been proposed that PDGFB acts as a mitogen in DP cells by autocrine stimulation of the PDGF receptor. It is encouraging that inhibitory effects of the PDGF receptor tyrosine kinase antagonist imatinib mesylate have been demonstrated in vivo; such targeted therapies might be warranted in the near future for treatment of the few DP cases not manageable by surgery.

Malignant solitary fibrous tumor of the pleura: report of a case with cytogenetic analysis

The majority of solitary fibrous tumors (SFTs) of the pleura are benign, but 10-30% locally recur or metastasize. Pathogenic factors relevant to the determinism of their biological properties are largely unknown. Cytogenetic data on SFTs of the pleura are sparse. We report herein a case of a malignant SFT of the pleura where successful karyotyping was obtained from the primary and recurrent tumors. The initial karyotype showed two abnormal clones: 48, XY; +8; +8; del(9)(q22; q32) [19] and 46, XY, t(1;16)(q25;p12) [7]. Culture of the recurrent tumor yielded one clone identical to the dominant clone of the initial karyotype. Demonstration of a recurrent abnormal karyotype largely supports its relevance to the malignant clone and suggests a role of supernumerary chromosome(s) 8 in the determinism of malignant behavior in SFT.

Cytogenetic findings in a case of nodular fasciitis of subclavicular region

We report a case of nodular fasciitis with a reciprocal translocation involving both homologues of chromosome 15 [46,XX,t(15;15)(q13;q25)]. This is the third case of nodular fasciitis with involvement of chromosome 15. Two genes that are involved in either wound healing and/or tumorigenesis have been mapped to chromosome 15. One of the genes, the keratinocyte growth factor or fibroblast growth factor 7 (KGF or FGF7) was mapped to the 15q22 region, which was involved in a cytogenetic rearrangement in one case of nodular fasciitis. KGF is implicated in wound healing, healing lung injuries and tumorigenesis of various cancers such as breast and prostate. The second gene involved is TRKC or NTRK3 mapped to the 15q25 region. TRKC is implicated in congenital fibrosarcoma, a benign proliferation of fibroblasts. The breakpoint and overexpression of the protein in our case further suggest a possible involvement of TRKC.

Treatment of infantile fibrosarcoma with chemotherapy and surgery: results from the Dana-Farber Cancer Institute and Children's Hospital, Boston

PURPOSE

To retrospectively evaluate the treatment and outcome of patients diagnosed with infantile fibrosarcoma at the Dana-Farber Cancer Institute and Children's Hospital, Boston.

PATIENTS AND METHODS

Between 1982 and 1998, a total of 11 infants were diagnosed pathologically with infantile fibrosarcoma. A retrospective chart review was conducted to determine the extent of surgical therapy and chemotherapy required for a favorable clinical outcome. Cytogenetic findings were reviewed and archived tumor specimens were analyzed, when available, for the presence of the TEL/TRKC fusion gene.

RESULTS

Three patients had primary surgical resection with negative pathologic margins and have been lost to follow-up. Two patients received chemotherapy only after limited biopsy or subtotal resection and are alive with no evidence of disease 8 and 18 years from diagnosis. Four patients had limited biopsies followed by chemotherapy with delayed resection. One of these four patients had negative margins and received no further chemotherapy. The other three of these patients had positive microscopic margins; two of them received postoperative chemotherapy while the third did not. All four are currently alive with no evidence of disease. Two patients had progressive disease within 7 and 10 months of diagnosis while on chemotherapy after subtotal resections. One of these two patients is dead of disease; the other is alive after palliative radiotherapy. Seven patients had archived or frozen tissue available for molecular analysis. All seven had evidence of TEL gene rearrangement; six exhibited the TEL/TRKC fusion. Six patients had characteristic trisomies previously reported to be associated with infantile fibrosarcoma.

CONCLUSIONS

Previously reported series of treatment outcomes in infantile fibrosarcoma have been limited to very few patients due to the rare occurrence of this tumor. In our experience, initial chemotherapy combined with surgery has been successful for most cases. When disease progression occurred, it was within one year of diagnosis. There was no development of distant metastases in the patients with progressive disease. The role of additional chemotherapy for microscopic margins after local control is not clear. We found a high incidence of the TEL/TRKC fusion gene, confirming its utility in diagnosis. We propose a uniform approach to treatment to gather clinical and biologic information about this rare and curable disease.