Sclerosing rhabdomyosarcoma in adults: report of four cases of a hyalinizing, matrix-rich variant of rhabdomyosarcoma that may be confused with osteosarcoma, chondrosarcoma, or angiosarcoma

Adult and pediatric orbital rhabdomyosarcoma: comparison of characteristics and outcomes

INTRODUCTION

Rhabdomyosarcoma (RMS) is a common pediatric orbital malignancy but is extremely rare in adults. This study assesses clinical and radiographic features, management, and outcomes in adult orbital RMS patients with comparison to pediatric patients.

METHODS

A retrospective chart review from 2000-2023 at Bascom Palmer Eye Institute was conducted evaluating patients aged 0 to 100-years-old with biopsy-confirmed orbital RMS. Medical records were reviewed for demographics, clinical features, imaging, histopathology, management, and outcomes. Statistical analysis was conducted with Mann-U Whitney and chi-squared testing.

RESULTS

Twenty-four patients were included, 15 children (mean age 6.4 ± 4.4 years) and 9 adults (35.7 ± 12.4 years). Patients in both groups presented with eyelid edema followed by proptosis with similar symptom duration (p = 0.31). Lesions were frequently located medially and inferiorly in both groups. At presentation, adults had significantly more metastatic disease in addition to bone, extraocular muscle, intracranial, and parameningeal involvement. The most common pediatric RMS subtype was embryonal (80%), whereas most adults were alveolar (77.8%, p = 0.001). Treatment in both groups frequently included chemoradiation. Both groups demonstrated similar local recurrence (p = 0.72), overall survival (p = 0.86), and ophthalmologic sequelae (p = 0.45), although pediatric follow-up duration was notably longer.

CONCLUSIONS

To our knowledge, this study is the largest report of adult orbital RMS from a single institution, highlights key comparisons in features and outcomes between adult and pediatric orbital RMS, and provides an updated literature review. While pediatric and adult orbital RMS clinical presentations are similar, adult disease more often demonstrates aggressive features, including alveolar subtype, local structure involvement, and lower disease-free survival.

Rhabdomyosarcoma: Updates on classification and the necessity of molecular testing beyond immunohistochemistry

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and adolescents under the age of 20. The current World Health Organization (WHO) classification for soft tissue and bone tumors recognizes 4 distinct subtypes of RMS based on clinicopathological and molecular genetic features: embryonal, alveolar, spindle cell/sclerosing and pleomorphic subtypes. However, with the increased use of molecular techniques, the classification of rhabdomyosarcoma has been evolving rapidly. New subtypes such as osseus RMS harboring TFCP2/NCOA2 fusions or RMS arising in inflammatory rhabdomyoblastic tumor have been emerging within the last decade, adding to the complexity of diagnosing skeletal muscle tumors. This review article provides an overview of classically recognized distinctive subtypes as well as new, evolving subtypes and discusses important morphologic, immunophenotypic and molecular genetic features of each subtype including recommendations for a diagnostic approach of malignant skeletal muscle neoplasms.

Multifaceted Spindle Cell/Sclerosing Rhabdomyosarcoma With Role of Immunohistochemistry in Avoiding Misdiagnosis: A Multi-Institutional Study of 45 Distinct Tumors

Background. Spindle cell/sclerosing rhabdomyosarcoma is a rare neoplasm and has an aggressive clinical course. Because of its rarity, we performed a multi-institutional collaboration to comprehend the overarching clinical, histopathological, and immunohistochemical characteristics of a cohort of spindle cell/sclerosing rhabdomyosarcoma. Materials and Methods. Forty-five patients with spindle cell/sclerosing rhabdomyosarcoma were identified. Demographics, clinical, histopathological, and immunohistochemistry data were reviewed and recorded. Results. The patients' age ranged from 1 to 85 years with a male to female ratio of 1.2:1. There were 15 children/adolescents and 30 adults. Eighteen (40%) tumors were located in the head and neck region. Twenty-four (53%) tumors displayed a bimorphic cellular arrangement with hypercellular areas having short, long, and sweeping fascicular and herringbone pattern, and hypocellular areas with stromal sclerosis and associated hyalinized and/or chondromyxoid matrix. Histomorphological differentials considered were leiomyosarcoma, malignant peripheral nerve sheath tumor, fibrosarcoma, nodular fasciitis, liposarcoma, synovial sarcoma, sarcomatoid carcinoma, solitary fibrous tumor, dermatofibrosarcoma protuberans, and schwannoma. Six tumors exhibited marked stromal sclerosis. The myogenic nature was confirmed by immunohistochemistry. Positivity for at least one skeletal muscle-associated marker (MyoD1 and/or myogenin) was observed. Conclusion. Spindle cell/sclerosing rhabdomyosarcoma diagnosis can be challenging as a number of malignant spindle cell neoplasm mimic this entity. Thus a correct diagnosis requires immunohistochemical work up with a broad panel of antibodies. In view of rarity of this neoplasm, further studies on a large cohort of patients with clinical follow-up data are needed for a better understanding of this tumor.

Biological Role and Clinical Implications of MYOD1L122R Mutation in Rhabdomyosarcoma

Major progress in recent decades has furthered our clinical and biological understanding of rhabdomyosarcoma (RMS) with improved stratification for treatment based on risk factors. Clinical risk factors alone were used to stratify patients for treatment in the European Pediatric Soft Tissue Sarcoma Study Group (EpSSG) RMS 2005 protocol. The current EpSSG overarching study for children and adults with frontline and relapsed rhabdomyosarcoma (FaR-RMS NCT04625907) includes FOXO1 fusion gene status in place of histology as a risk factor. Additional molecular features of significance have recently been recognized, including the MYOD1^L122R gene mutation. Here, we review biological information showing that MYOD1^L122R blocks cell differentiation and has a MYC-like activity that enhances tumorigenesis and is linked to an aggressive cellular phenotype. MYOD1^L122R mutations can be found together with mutations in other genes, such as PIK3CA, as potentially cooperating events. Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, ten publications in the clinical literature involving 72 cases were reviewed. MYOD1^L122R mutation in RMS can occur in both adults and children and is frequent in sclerosing/spindle cell histology, although it is also significantly reported in a subset of embryonal RMS. MYOD1^L122R mutated tumors most frequently arise in the head and neck and extremities and are associated with poor outcome, raising the issue of how to use MYOD1^L122R in risk stratification and how to treat these patients most effectively.

Molecular assessment of paratesticular rhabdomyomas demonstrates recurrent findings, including a novel H3C2 p.K37I mutation

Rhabdomyomas are benign tumors with skeletal muscle differentiation that are broadly divided into cardiac and extracardiac types. The latter demonstrate a predilection for head and neck and genital locations and are further subclassified into adult-type rhabdomyoma (ATRM), fetal-type rhabdomyoma (FTRM) and genital rhabdomyoma (GRM). Most extracardiac rhabdomyomas that arise in paratesticular tissues have a somewhat distinctive morphology and have been termed sclerosing rhabdomyomas (SRM). Therefore, we hypothesized that these tumors may harbor recurrent genetic alterations. In this study, we assessed 15 paratesticular rhabdomyomas (11 initially classified as SRM, 2 cellular FTRM and 2 ATRM) using massively parallel DNA and RNA sequencing. Five of 14 successfully sequenced cases harbored a novel H3C2 p.K37I mutation (4 SRM and 1 ATRM). This mutation replaced a highly conserved lysine residue that is a target for epigenetic modifications and plays a role in regulation of DNA replication. Moreover, 4 tumors (2 cellular FTRM, 1 case initially diagnosed as SRM and 1 ATRM) had complex copy number profiles characterized by numerous chromosome-level and arm-level copy number gains, consistent with a ploidy shift. Rereview of the SRM with copy number gains demonstrated that it was significantly more cellular and had a more prominent fascicular architecture than the rest of the SRMs included in this series. Therefore, it was retrospectively reclassified as a cellular FTRM. In conclusion, this study demonstrated that paratesticular rhabdomyomas harbor recurrent somatic H3C2 p.K37I mutations and ploidy shifts.

Cytomorphology of spindle cell/sclerosing rhabdomyosarcoma, including MYOD1 (LI22R) mutation result

Spindle cell/sclerosing rhabdomyosarcoma (RMS), characterized by MYOD1 (L122R) mutation in a subset of cases is a newly described subtype of RMS. Presently, there is no documentation of cytomorphological features, especially of sclerosing RMS. Case 1: A 24-year-old male presented with pain and swelling in his wrist for a one-year duration. MRI revealed a well-defined soft tissue lesion measuring 5.3 cm, encasing the lower end of the ulna. Fine-needle aspiration cytology (FNAC) smears revealed clusters of tumor cells with round to oval to spindle-shaped nuclei, scant to moderate amount of cytoplasm with the wisps of the metachromatic stroma. Histopathological examination revealed a malignant tumor comprising cells with polygonal to spindle-shaped nuclei, arranged in a sclerotic stroma. Immunohistochemically, the tumor cells were positive for desmin, myogenin, and MYOD1. A diagnosis of sclerosing RMS was offered. Furthermore, the tumor revealed MYOD1 (L122R) mutation. Case 2: A 43-year-old male presented with a 4-month history of "nasal stuffiness" and pressure. Imaging revealed a poorly defined infiltrative lesion in his nasal cavity. FNAC smears revealed loose and tightly cohesive clusters of malignant cells with oval to spindle-shaped nuclei, a moderate amount of ill-defined bluish to finely vacuolated cytoplasm, and focal streak artifact with interspersed stromal fragments. Histopathological examination revealed a malignant tumor composed of oval to spindle-shaped nuclei, embedded in a variably hyalinized stroma. Immunohistochemically, the tumor cells were positive for desmin, and myogenin. Diagnosis of spindle cell/sclerosing RMS was offered. The present study constitutes one of the first documentation of cytomorphological features of two rare cases of spindle cell/sclerosing RMS. The differential diagnoses and treatment-related implications are presented.

An Integrative Morphologic and Molecular Approach for Diagnosis of Rhabdomyosarcoma and Subclassification of Rhabdomyosarcoma

CONTEXT.—

Rhabdomyosarcoma, the most common soft tissue sarcoma of children, is currently classified into the following 4 subtypes: embryonal rhabdomyosarcoma, alveolar rhabdomyosarcoma, spindle cell/sclerosing rhabdomyosarcoma, and pleomorphic rhabdomyosarcoma, based on recent molecular genetic knowledge and morphologic features.

OBJECTIVE.—

To highlight the most recent advances of molecular genetic alterations, and to familiarize pathologists with most recent genotype and phenotype correlation in rhabdomyosarcoma.

DATA SOURCES.—

Data were derived from the World Health Organization Classification of Soft Tissue and Bone Tumors, fifth edition, recently published literature (PubMed), and clinical practice experience.

CONCLUSIONS.—

Current classification has been significantly impacted by genotype and phenotype correlation, especially with PAX-FOXO1 fusion-positive rhabdomyosarcoma versus fusion-negative rhabdomyosarcoma, and with emergence of 3 distinct new subtypes of spindle cell/sclerosing rhabdomyosarcoma. Although all rhabdomyosarcomas were considered to be a single diagnostic entity in the past, they are now considered to be a group of histologically similar but biologically diverse entities because their clinical behavior and underlying molecular alterations dramatically differ. This review outlines recent molecular genetic developments, corresponding morphologic features, and current challenges faced by pathologists in daily practice.

Evolving classification of rhabdomyosarcoma

Rhabdomyosarcomas comprise the single largest category of soft tissue sarcomas in children and adolescents in the United States, occurring in 4.5 million people aged below 20 years. Based on the clinicopathological features and genetic abnormalities identified, rhabdomyosarcomas are classified into embryonal, alveolar, spindle cell/sclerosing and pleomorphic subtypes. Each subtype shows distinctive morphology and has characteristic genetic abnormalities. This review discusses the evolution of the classification of rhabdomyosarcoma to the present day, together with a discussion of key histomorphological and genetic features of each subtype and the diagnostic approach to these tumours.

Rhabdomyosarcoma: How Advanced Molecular Methods Are Shaping the Diagnostic and Therapeutic Paradigm

For the past 40 years, progress in rhabdomyosarcoma (RMS) has been focused on understanding its molecular basis and characterizing the mutations that drive its tumorigenesis and progression. Genetic predisposition to RMS has allowed discovery of key genetic pathways and driver mutations. Subclassification of RMS into embryonal (ERMS) and alveolar (ARMS) subtypes has shifted from histology to PAX-FOXO1 fusion status, and new driver mutations have been found in spindle cell RMS. Comprehensive molecular profiling leveraging genome-scale next-generation sequencing (NGS) indicates that the RAS/RAF/PI3K axis is mutated in the majority of ERMS and modulated by downstream effects of PAX-FOXO1 fusions in ARMS. Because of the continued poor outcome of high-risk RMS, a variety of molecular targets have been or are now being tested in current or recent therapy trials. New techniques such as single cell sequencing, spatial multi-omics, and CRISPR/Cas9 genome editing offer potential for further discovery, but a need for clinically annotated specimens persists.

Tongue Spindle Cell Rhabdomyosarcoma: A Rare Case Report and Literature Review

Rhabdomyosarcoma (RMS) is a malignant soft tissue neoplasm with its origin in the skeletal muscle and is extremely rare in adults. By the World Health Organization (WHO), a new variant of RMS has been classified, i.e. the spindle cell (Sc) and sclerosing (S) RMS. While the Sc-RMS shows intersecting fascicles of nonpleomorphic spindle cells, the S-RMS is characterized by a marked hyalinization in a pseudovascular growth pattern associated with round-to-spindled tumour cells. According to the analysed data, the Sc/S-RMS variant has a worse outcome than other variants. The new classification of the Sc/S-RMS variant is valuable to the clinical practice. There are not many oral Sc/S-RMS cases reported. The aim of this paper is to demonstrate that an early diagnosis, an adequate treatment and a multidisciplinary approach have a positive effect on the prognosis of the patient. In this study, we analyse a new case of Sc-RMS variant in a young adult with an early diagnosis and a favourable outcome as a result of an appropriated multidisciplinary treatment: early surgery, radiotherapy and chemotherapy treatment.

Sclerosing Epithelioid Fibrosarcoma: A Distinct Sarcoma With Aggressive Features

Since its original description in 1995, the concept of sclerosing epithelioid fibrosarcoma (SEF) as a distinctive tumor has evolved in the literature. Subsequent studies suggested that the presence of low grade fibromyxoid sarcoma (LGFMS)-like zones, occasional FUS gene rearrangements, and immunoreactivity for MUC4 all pointed to a close inter-relationship with LGFMS; however, more recent studies showed that SEF is genetically distinct from LGFMS with predominantly EWSR1-CREB3L1 fusion and complex secondary genomic alterations. To better understand the relationship between these tumors, we studied 51 cases of SEF, the largest reported series to date, and directly compared them to a previously published series of LGFMS from the same institution. The male-to-female ratio was 1.4:1 with a median age of 45 years. Tumors occurred primarily in the lower extremity (12), intra-abdominal area/visceral organs (9) and chest wall/paraspinal region (9) with a median size of 8.2 cm. The median follow-up was 49 months in 45 patients: 12 developed local recurrences and 36 developed metastases, mainly to lung and bone. Molecular studies showed EWSR1 gene rearrangement in 13 cases, 3' deletion of EWSR1 in 6, monosomy for EWSR1 in 2; FUS gene rearrangements in 3; EWSR1-CREB3L1 fusion in 7; EWSR1-CREB3L2 fusion in 1; and YAP1-KMT2A fusion in 2. Overall survival of SEF was significantly less compared with LGFMS (P≤0.0001). These results indicate that SEF is a distinct sarcoma that behaves more aggressively than LGFMS with a shorter survival, higher metastatic rate, and greater propensity to involve deep soft tissue and bone.

Pathology of childhood rhabdomyosarcoma: A consensus opinion document from the Children's Oncology Group, European Paediatric Soft Tissue Sarcoma Study Group, and the Cooperative Weichteilsarkom Studiengruppe

The diagnosis and classification of rhabdomyosarcoma (RMS) has undergone several shifts over the last 30 years. While the main diagnostic categories remained the same, changes in the histologic criteria necessary for diagnosis, as well as varied reliance on immunohistochemical and molecular data over time, have created confusion, particularly regarding how these shifts impacted risk stratification and enrollment onto clinical trials. The goal of this report is to review the evolution and current status of RMS diagnosis, focusing on diagnostic criteria in the Children's Oncology Group (COG), the European Paediatric Soft Tissue Sarcoma Group (EpSSG), and the Cooperative Weichteilsarkom Studiengruppe (CWS). In addition, we emphasize research tools used to classify RMS and address biological questions within current clinical trials run by each group. The INternational Soft Tissue SaRcoma ConsorTium (INSTRuCT) initiative will maximize potential to optimize risk stratification by recognizing and accounting for differences in historical data and current practices.

Challenges in the Diagnosis of Pediatric Spindle Cell/Sclerosing Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma, representing approximately 40% of all pediatric soft tissue sarcomas. The spindle cell/sclerosing subtype of RMS (SSRMS) accounts for roughly 5% to 10% of all cases of adult and pediatric RMS. Historically, SSRMS were described as paratesticular tumors with an excellent outcome. However, more recent studies have identified unique molecular subgroups of SSRMS, including those with MYOD1 mutations or VGLL2/NCOA2 fusions, which have widely disparate outcomes. The goal of this article is to better describe the biological heterogeneity of SSRMS, which may allow the pathologist to provide important prognostic information.

Histiocyte-rich rhabdomyoblastic tumor: a report of two cases and a review of the differential diagnoses

Histiocyte-rich rhabdomyoblastic tumor is a recently described skeletal muscle neoplasm of uncertain malignant potential, characterized by slow growth, a fibrous capsule containing peripheral lymphoid aggregates, spindle-to-epithelioid cells with a rhabdomyoblastic immunophenotype, and a dense histiocytic infiltrate. It most commonly arises within the muscles of the lower legs and trunk in young-to-middle-aged men, and initial reports suggest indolent behavior. In this paper, we present two additional cases of histiocyte-rich rhabdomyoblastic tumor with similar clinicopathologic features and discuss the differential diagnosis including its overlap with inflammatory leiomyosarcoma.

Establishment and characterization of NCC-ssRMS1-C1: a novel patient-derived spindle-cell/sclerosing rhabdomyosarcoma cell line

Spindle-cell/sclerosing rhabdomyosarcoma (ssRMS) is a rare subtype of rhabdomyosarcoma, characterized by unique pathological features. Although distinctive molecular backgrounds such as frequent mutations in MyoD1 have been reported, optimized therapy has not been fully developed, and further investigations are required. Patient-derived cancer models are critical tools for basic and pre-clinical studies. However, there is no model for ssRMS. Thus, this study aimed to develop a novel cell line from the tumor tissue of a patient with ssRMS. Using surgically resected tissue, we successfully established this cell line, named NCC-ssRMS1-C1. These cells exhibited spindle-shape morphology, consistent with the pathological observations of the original tumor tissue. Genetic studies demonstrated that NCC-ssRMS1-C1 cells retained original copy number alterations and the typical point mutation in MyoD1. Malignant phenotypes such as proliferation, spheroid formation, and invasion were confirmed in vitro by studying NCC-ssRMS1-C1 cells. Upon screening an anti-cancer agent library, sensitivity to conventional chemotherapeutic agents such as actinomycin D was revealed. We conclude that the NCC-ssRMS1-C1 cell line will be a useful resource for basic and pre-clinical studies.

The expanding morphological and genetic spectrum of MYOD1-mutant spindle cell/sclerosing rhabdomyosarcomas: a clinicopathological and molecular comparison of mutated and non-mutated cases

AIMS

Spindle cell/sclerosing rhabdomyosarcomas (SC/SRMS) feature spindled and/or rounded rhabdomyosarcomatous cells within variably hyalinised stroma. Only 30-67% of SC/SRMSs harbour neomorphic MYOD1 p.L122R mutations, indicating heterogeneity in this RMS type. We compared MYOD1-mutant and non-mutant cases to characterise the histological and genetic spectrum of mutated SC/SRMS.

METHODS AND RESULTS

Seventeen RMSs with spindled, sclerosing or hybrid histology were sequenced to identify MYOD1 and PIK3CA mutations and reappraised to assess histological features and myogenic immunophenotypes. Twelve SC/SRMSs harboured MYOD1 mutations, including homozygous p.L122R (n = 8), heterozygous p.L122R (n = 3) and heterozygous p.E118K (n = 1). MYOD1-mutant tumours affected nine females and three males aged 8-64 years (median = 22.5), had a median size of 4.2 cm (range = 2-22) and involved the head and neck (n = 7), extremities (n = 4) and mediastinum (n = 1). Fascicular/spindle histology was predominant in four cases, including one with heterologous lipoblasts in focally myxoid stroma. Four sclerosing cases mainly comprised rounded cells, including one with multinucleated tumour cells. Four cases were histologically hybrid. The only PIK3CA (p.H1047R) mutation was detected in a predominantly spindled MYOD1-p.L122R-mutated case, but not in its laser-microdissected lipoblast-containing area. All MYOD1-mutant cases exhibited diffuse MYOD1 expression but patchy myogenin reactivity. At final follow-up (median = 13.5 months), recurrences (n = 4), metastases (n = 2) or both (n = 1) occurred in seven MYOD1-mutant cases; one had died of disease. Five non-mutated cases were reclassified as spindle embryonal (n = 3), dense embryonal (n = 1) and unclassifiable (n = 1) RMSs.

CONCLUSION

MYOD1-mutant RMSs are uncommonly mutated with PIK3CA and behave aggressively with an expanded morphological and genetic spectrum, including lipoblastic differentiation, multinucleated cells and the alternative p.E118K mutation.

Histiocyte-rich rhabdomyoblastic tumor: rhabdomyosarcoma, rhabdomyoma, or rhabdomyoblastic tumor of uncertain malignant potential? A histologically distinctive rhabdomyoblastic tumor in search of a place in the classification of skeletal muscle neoplasms

Skeletal muscle tumors are traditionally classified as rhabdomyoma or rhabdomyosarcoma. We have identified an unusual adult rhabdomyoblastic tumor not clearly corresponding to a previously described variant of rhabdomyoma or rhabdomyosarcoma, characterized by a very striking proliferation of non-neoplastic histiocytes, obscuring the underlying tumor. Ten cases were identified in nine males and one female with a median age of 43 years (range 23-69 years). Tumors involved the deep soft tissues of the trunk (N = 4), lower limbs (N = 4), and neck (N = 2). Tumors were well-circumscribed, nodular masses, frequently surrounded by a fibrous capsule containing lymphoid aggregates and sometimes calcifications. Numerous foamy macrophages, multinucleated Touton-type giant cells, and sheets/fascicles of smaller, often spindled macrophages largely obscured the underlying desmin, MyoD1, and myogenin-positive rhabdomyoblastic tumor. Cases were wild type for MYOD1 and no other mutations or rearrangements characteristic of a known subtype of rhabdomyoma or rhabdomyosarcoma were identified. Two of four cases successfully analyzed using a next-generation sequencing panel of 170 common cancer-related genes harbored inactivating NF1 mutations. Next-generation sequencing showed no gene fusions. Clinical follow (nine patients; median 9 months; mean 23 months; range 3-124 months) showed all patients received wide excision; four patients also received adjuvant radiotherapy and none received chemotherapy. At the time of last follow-up, all patients were alive and without disease; no local recurrences or distant metastases occurred. We hypothesize that these unusual tumors represent rhabdomyoblastic tumors of uncertain malignant potential. Possibly over time they should be relegated to a new category of skeletal muscle tumors of intermediate (borderline) malignancy.

MYOD1-mutant spindle cell and sclerosing rhabdomyosarcoma: an aggressive subtype irrespective of age. A reappraisal for molecular classification and risk stratification

Sclerosing and spindle cell rhabdomyosarcoma is a rare histologic subtype, designated in the latest WHO classification as a stand-alone pathologic entity. Three genomic groups have been defined: an infantile subset of spindle cell rhabdomyosarcoma harboring VGLL2-related gene fusions, a MYOD1-mutant subset commonly associated with sclerosing morphology, and a subset lacking recurrent genetic abnormalities. In this study, we focus on MYOD1-mutant rhabdomyosarcoma to further define their clinicopathologic characteristics and behavior in a larger patient cohort. We investigated 30 cases of MYOD1-mutant rhabdomyosarcoma (12 previously reported and 18 newly diagnosed) with an age range of 2-94 years, including 15 children. All cases showed morphology within the spectrum of spindle cell/sclerosing rhabdomyosarcoma (8 cases showing pure sclerosing morphology, 8 cases  showing pure spindle cell morphology and 14 cases showing a hybrid phenotype of spindle, sclerosing and primitive undifferentiated areas). All tumors harbored either homozygous or heterozygous MYOD1 (p.L122R) exon 1 mutations. In 10 (33%) cases, a co-existent PIK3CA mutation was identified. Hot-spot mutations in NRAS and HRAS were each identified in a single case, respectively. Follow-up was available on 22 (73%) patients with a median duration of 28 months. Local recurrence was seen in 12 (55%) and distant recurrence in 12 (55%) cases, despite multimodality chemoradiation therapy. At last follow-up, 15 (68%) patients died of the disease, one patient was alive with disease and five had no evidence of disease. The prognosis was equally poor in pediatric and adult patients. In conclusion, MYOD1 mutation defines an aggressive rhabdomyosarcoma subset, with poor outcome and response to therapy, irrespective of age. Given that this distinct molecular subtype is characterized by an aggressive biologic behavior compared to other genetic subtypes of spindle and sclerosing rhabdomyosarcoma, the MYOD1 genotype should be used as a molecular marker in both subclassification and prognostication of rhabdomyosarcoma.

Combined Sclerosing and Spindle Cell Rhabdomyosarcoma in Previous Craniotomy Site: A Case Report and a Review of the Literature

Sclerosing rhabdomyosarcoma (RMS) is a rare subtype of RMS with unique prominent stromal hyalinization and a pseudovascular architecture. It overlaps morphologically with spindle cell RMS and poses both diagnostic and therapeutic challenges because of its rarity and aggressive clinical course. In this article, we report a case of sclerosing RMS arising from a prior craniotomy site, which demonstrated both sclerosing and spindle cell components. A literature review of RMS with sclerosing morphology identified 122 cases. Our review documents the following: sclerosing RMS occurs in both childhood and adult populations, has a predilection for the head and neck areas, and has a worse prognosis in adults. Sclerosing RMS harbors a high frequency of MYOD1 mutations, conferring a poor clinical outcome. Sclerosing RMS and spindle RMS likely represent a morphologic spectrum of one entity.

Ear and Temporal Bone Pathology: Neural, Sclerosing and Myofibroblastic Lesions

Neural, sclerosing, and myofibroblastic lesions of the ear and temporal bone present diagnostic challenges for both clinicians and pathologists due to significant overlap in their clinical presentations, histologic appearances, and immunohistochemical profiles. While some of these lesions, such as schwannomas, are relatively common, others are rendered even more difficult because they are encountered very rarely in routine surgical pathology practice. This review is intended to provide an update on the pathology of some of the most commonly encountered primary diagnostic entities for the ear and temporal bone, and includes the following neural lesions: schwannoma, meningioma, and encephalocele/meningocele. Sclerosing lesions that will be discussed include spindle cell and sclerosing rhabdomyosarcoma, sclerosing epithelioid fibrosarcoma, and sclerosing paraganglioma. Finally, myofibroblastic lesions that will be reviewed are nodular fasciitis, IgG4-related disease, and solitary fibrous tumor. For each of these lesions, the differential diagnosis and useful ancillary tests will be discussed in the context of a broad range of additional primary and secondary lesions.

Spindle cell rhabdomyosarcoma of bone with FUS-TFCP2 fusion: confirmation of a very recently described rhabdomyosarcoma subtype

AIMS

Rhabdomyosarcomas of bone are extremely rare, with fewer than 10 reported cases. A very rare subtype of spindle cell/sclerosing rhabdomyosarcoma harbouring a FUS-TFCP2 fusion and involving both soft tissue and bone locations has been reported very recently. We report only the fourth case of this unusual, clinically aggressive rhabdomyosarcoma.

MATERIAL AND RESULTS

A previously well 72-year-old male presented with a destructive lesion of the mandible. Morphological and immunohistochemical study of a needle biopsy and the subsequent resection showed a spindle cell rhabdomyosarcoma. RNA-seq, RT-PCR and FISH confirmed the presence of the FUS-TFCP2 fusion.

CONCLUSIONS

Spindle cell rhabdomyosarcomas carrying the FUS-TFCP2 fusion are very rare rhabdomyosarcoma variants with osseous predilection. The classification and differential diagnosis of this unusual molecular variant of spindle cell/sclerosing rhabdomyosarcoma are discussed.

Mesenchymal chondrosarcomas showing immunohistochemical evidence of rhabdomyoblastic differentiation: a potential diagnostic pitfall

The diagnosis of mesenchymal chondrosarcoma, a distinctive biphasic malignant neoplasm harboring the HEY1-NCOA2 gene fusion and consisting of primitive round to spindled cells admixed with foci of relatively mature hyaline cartilage, is usually straightforward by morphologic evaluation alone. However, in the setting of a limited biopsy, specimens lacking cartilage generate a broad differential diagnosis, encompassing a variety of other primitive sarcomas, including spindle cell/sclerosing rhabdomyosarcoma. Although a small number of cases of mesenchymal chondrosarcoma with aberrant skeletal muscle marker expression have been reported, pathologists are largely unaware of this potential diagnostic pitfall. We report 6 additional cases of mesenchymal chondrosarcoma showing expression of multiple skeletal muscle markers, including one case initially misdiagnosed as "spindle cell/sclerosing rhabdomyosarcoma" on needle biopsy. Awareness of this phenomenon and judicious application of molecular diagnostic testing for the HEY1-NCOA2 fusion are critical to avoid misclassification of mesenchymal chondrosarcoma as rhabdomyosarcoma, with potentially adverse patient impact.

Modern Computer Technologies Facilitate Communication with a Young Cancer Patient

Aim

The aim of this paper is to show how new technologies may help the communication process in clinical practice in a department providing supportive care to patients undergoing cancer treatment.

Method

Communication via Internet chat between the psychologist and a young man who sees chatting on the Internet as a natural and familiar mode of expression was shown to be useful.

Results

The Internet link enabled us to open a communication channel with the patient and to have a conversation that would otherwise have been impossible.

Conclusions

Although verbal communication is the most important way to communicate among people, Internet communications are certainly an opportunity worth exploring, because they may open up new channels for cancer patients whose ability to speak is restricted. We might imagine using this approach in pediatric oncology, with adolescents and preadolescents, and with young adults like the patient discussed here. The case discussed highlights the enormous difference between the mere transfer of information and genuine communication, the latter involving an encounter with the patient.

Spindle cell/sclerosing rhabdomyosarcoma with intracranial invasion without destroying the bone of the skull base: a case report and literature review

Spindle cell/sclerosing rhabdomyosarcoma (ssRMS) is a new subtype of rhabdomyosarcoma included in the World Health Organization soft tissue and bone tumor classification in 2013. Despite the increasing number of reported cases of ssRMS, the imaging characteristics of ssRMS are not established. Herein, we present the case of an elderly Japanese woman with ssRMS of the masticator space with intracranial invasion without destruction of the adjacent bone. Attention should be paid to the presence of intracranial infiltration that may indicate a worse prognosis. Tumor growth without bone destruction could be a key finding to differentiate ssRMSs from conventional subtypes of rhabdomyosarcoma.

Rhabdomyosarcoma, Spindle Cell/Sclerosing Variant: A Clinical and Histopathological Examination of this Rare Variant with Three New Cases from the Oral Cavity

Spindle cell/sclerosing rhabdomyosarcoma (S-ScRMS) was recently recognized in 2013 by the World Health Organization (WHO) as a stand-alone entity (Parham et al., WHO classification of tumours of soft tissue and bone, IARC Press, Lyon, 2013). Historically, the spindle cell and sclerosing variants were subcategorized under embryonal type rhabdomyosarcoma. Current data supports that certain S-ScRMS cases have a more aggressive clinical course with reduction of long-term survival, and those found in the head and neck region often exhibit extensive local recurrence. Furthermore, due to variable histopathologic appearances and immunohistochemical findings, misdiagnosis is common. We aim to report the variability in histopathologic patterns, immunohistochemical findings, radiographic features, and clinical data on three new cases of S-ScRMS presenting in the oral cavity of young adult males (ages 22, 24, and 39 years). The English-language literature on S-ScRMS is briefly reviewed as well.

Update on molecular findings in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common malignant soft tissue tumour in children and adolescents. Histologically RMS resembles developing fetal striated skeletal muscle. RMS is stratified into different histological subtypes which appear to influence management plans and patient outcome. Importantly, molecular classification of RMS seems to more accurately capture the true biology and clinical course and prognosis of RMS to guide therapeutic decisions. The identification of PAX-FOXO1 fusion status in RMS is one of the most important updates in the risk stratification of RMS. There are several genes close to PAX that are frequently altered including the RAS family, FGFR4, PIK3CA, CTNNB1, FBXW7, and BCOR. As with most paediatric blue round cell tumours and sarcomas, chemotherapy is the key regimen for RMS therapy. Currently there are no direct inhibitors against PAX-FOXO1 fusion oncoproteins and targeting epigenetic cofactors is limited to clinical trials. Failure of therapy in RMS is usually related to drug resistance and metastatic disease. Through this review we have highlighted most of the molecular aspects in RMS and have attempted to correlate with RMS classification, treatment and prognosis.

MYOD1 (L122R) mutations are associated with spindle cell and sclerosing rhabdomyosarcomas with aggressive clinical outcomes

Recurrent mutations in the myogenic transcription factor MYOD1 and PIK3CA were initially described in a subset of embryonal rhabdomyosarcomas. Recently, two independent studies demonstrated presence of MYODI (L122R) mutations as the basis to re-classify a spindle cell rhabdomyosarcoma, along with a sclerosing rhabdomyosarcoma, distinct from an embryonal rhabdomyosarcoma. We analyzed a much larger cohort of 49 primary rhabdomyosarcoma tumor samples of various subtypes, collected over a period of 9 years, for the presence of MYOD1 (L122R), PIK3CA (H1047), and PIK3CA (E542/E545) mutations, along with immunohistochemical analysis of desmin, myogenin, and MYOD1. Although activating PIK3CA mutations were absent across the sample set analyzed, we report 20% MYOD1 (L122R) mutation in rhabdomyosarcomas, found exclusively in 10 of 21 spindle cell and sclerosing rhabdomyosarcomas, occurring mostly in the head and neck region along with extremity sites (64%), than the paratesticular and intra-abdominal sites. Furthermore, while all 10 MYOD1 mutant spindle cell and sclerosing rhabdomyosarcoma samples showed diffuse and strong MYOD1 immunoexpression, 7 of 31 samples of rhabdomyosarcoma with wild-type MYOD1 were negative for MYOD1 expression. Clinically, a striking correlation was found between MYOD1 mutation and the clinical outcomes available for 15 of 21 cases: 5 of 7 patients with spindle cell and sclerosing rhabdomyosarcomas, harboring MYOD1 mutation, were alive-with-disease and 2 of 8 patients with spindle cell and sclerosing rhabdomyosarcomas, with mutant MYOD1, were free-of-disease. Taken together, we present the first report of MYOD1 (L122R) mutation in the largest cohort of 49 rhabdomyosarcomas reported so far, that are associated with a relatively aggressive clinical course. Moreover, consistent with the earlier two studies, this study further reinforces a relationship between spindle cell and the sclerosing rhabdomyosarcoma-now recognized as a single subtype, distinct from an embryonal rhabdomyosarcoma.

Head and Neck Rhabdomyosarcoma: Clinical and Pathologic Characterization of Seven Cases

Head and neck rhabdomyosarcoma occurs frequently in children and adolescents, and has been well studied in that population. In contrast, it is rare in adults and is not as well characterized clinically and pathologically. Seven cases of adult rhabdomyosarcoma occurring in head and neck were retrieved from the archives of Department of Pathology and Division of Oral Pathology at University of Washington. Radiologic findings and clinical history, as well as pathologic findings from hematoxylin and eosin slides and immunohistochemistry for myogenic markers were reviewed. A total of seven cases of rhabdomyosarcoma (two embryonal, three alveolar and two pleomorphic subtype) were reviewed. Patient ages ranged from 18 to 57 years (median 21 years). Classic and unique histologic features for each subtype, including post-treatment morphologic changes, were identified. Clinical follow-up information was available for 4 patients. 3 of 4 patients experienced recurrence, including two with distant metastasis. One patient died of disease progression 41 months after presentation. Head and neck rhabdomyosarcoma in adults can manifest both classic and unique histologic features for each subtype. In addition, recurrence and distant metastasis were observed, suggesting aggressive clinical behavior regardless of subtype.

A clinicopathologic study of head and neck rhabdomyosarcomas showing FOXO1 fusion-positive alveolar and MYOD1-mutant sclerosing are associated with unfavorable outcome

BACKGROUND

Based on their distinctive histologic and genetic features, the latest WHO classification of soft tissue tumors includes four pathologic variants of rhabdomyosarcoma (RMS): embryonal (ERMS), alveolar (ARMS), spindle cell-sclerosing (SRMS-ScRMS) and pleomorphic RMS. The aim of this study focused on a detailed clinicopathologic and survival analysis of head and neck RMS (HNRMS) using the latest pathologic and molecular criteria reflecting this new subclassification in a large cohort.

PATIENTS AND METHODS

Patients managed for HNRMS in our institution (1996-2015) were analyzed. The presence of a FOXO1 fusion was required for the classification of ARMS. MYOD1 mutations in SRMS-ScRMS were tested when material available. Univariate and multivariate analyses were performed to evaluate variables related to overall survival (OS).

RESULTS

Ninety-nine HNRMS patients (52 males and 47 females, mean of 16years) were included in the study after pathologic re-review. The most common location was parameningeal (PM) (n=64), followed by non-orbital/non-PM (n=25) and orbital (n=10). There were 53 ERMS, 33 fusion-positive ARMS and 13 SRMS-ScRMS [SRMS (8); ScRMS (5)]. The 5-year OS rate for ERMS patients was significantly higher (82%) compared to ARMS (53%) and SRMS-ScRMS (50%) [SRMS (75%); ScRMS (30%)]. Univariate analysis showed that survival was dependent on histology (P=0.012), tumor size >5cm (P<0.001), regional lymph node involvement (P=0.002), metastasis at initial presentation (P<0.001), stage (P<0.001), and recurrence (P=0.002). Multivariate analysis confirmed histologic subtype to be significant (P=0.043).

CONCLUSION

Our findings reinforce that HNRMS is a heterogenous disease with ARMS and SRMS-ScRMS having an equally unfavorable outcome.

Epithelioid rhabdomyosarcoma: a clinicopathological study of seven additional cases supporting a distinctive variant with aggressive biological behaviour

We present our experience with seven cases of epithelioid rhabdomyosarcoma (RMS) to further characterise its clinicopathological features. There were five males and two females with ages ranging from 19 to 84 years (mean 56 years). Four tumours occurred in the somatic soft tissue, two in organs and one in the bone. The mean tumour size was 10.7 cm (range 3.5-15 cm). Histologically, six tumours were characterised by sheet-like growth of uniform epithelioid cells with large vesicular nuclei, prominent nucleoli, high mitotic activity and moderate to abundant amphophilic-to-eosinophilic cytoplasm. One tumour was composed of dyscohesive cells with rhabdoid appearance embedded in a myxoid matrix. Features suggestive of rhabdomyoblastic differentiation were absent. However, immunohistochemical study revealed skeletal muscle differentiation in all cases. Of note, focal expression of epithelial markers with co-expression of neuroendocrine markers was noted in five and three cases, respectively. Of six patients with follow-up, one experienced local recurrence and three developed metastases. To date, three patients have died of disease within 14 months. This study further demonstrates that epithelioid RMS represents a distinct variant of RMS with an aggressive behaviour. It may be misdiagnosed as poorly differentiated neuroendocrine carcinoma due to co-expression of epithelial and neuroendocrine markers.

Giant Sclerosing Oral Rhabdomyosarcoma-A Unique Case

We present a case of oral Rhabdomyosarcoma in a 50 years old man presenting with a huge mass in the oral cavity. Pre operative investigations showed the mass to be Rhabdomyosarcoma. The mass was excised and subjected to histopathogical and immunohistochemical examinations which confirmed to be Rhabdomyosarcoma.

Pediatric Sclerosing Rhabdomyosarcoma

Sclerosing rhabdomyosarcoma, a particular phenotypic variant of rhabdomyosarcoma initially described in the adult population, has emerged as a potential pitfall in the evaluation of pediatric sarcomas. Because of its densely hyalinized collagenous matrix and its occasional expression of a pseudovascular pattern of growth, sclerosing rhabdomyosarcoma has been at times misdiagnosed as chondrosarcoma, osteosarcoma, or angiosarcoma. We describe 3 pediatric patients with sclerosing rhabdomyosarcoma and provide a detailed description of its distinguishing pathologic features. Awareness about this rhabdomyosarcoma variant and careful immunophenotypical evaluation are necessary to establish the correct diagnosis. Although no specific genetic aberrations have been recognized, yet the cytogenetic findings in 2 tumors of this series suggest a link with embryonal rhabdomyosarcoma. It is likely that further genotyping will result in better nosologic delineation of sclerosing rhabdomyosarcoma and that it will uncover pathogenetically and prognostically relevant genes.

A Molecular Study of Pediatric Spindle and Sclerosing Rhabdomyosarcoma: Identification of Novel and Recurrent VGLL2-related Fusions in Infantile Cases

Sclerosing rhabdomyosarcoma (ScRMS) and spindle cell rhabdomyosarcoma (SRMS) have been recently reclassified as a stand-alone pathologic entity, separate from embryonal RMS. Genetically, a subset of the congenital cases display NCOA2 gene rearrangements, whereas tumors occurring in older children or adults harbor MYOD1 gene mutations with or without coexisting PIK3CA mutations. Despite these recent advances, a significant number of tumors lack known genetic alterations. In this study we sought to investigate a large group of pediatric SRMS/ScRMS, spanning a diverse clinical and pathologic spectrum, by using a combined fluorescence in situ hybridization, targeted DNA, and whole-transcriptome sequencing methodology for a more definitive molecular classification. A total of 26 SRMS and ScRMS cases were selected from the 2 participating institutions for the molecular analysis. Ten of the 11 congenital/infantile SRMS showed recurrent fusion genes: with novel VGLL2 rearrangements seen in 7 (63%), including VGLL2-CITED2 fusion in 4 and VGLL2-NCOA2 in 2 cases. Three (27%) cases harbored the previously described NCOA2 gene fusions, including TEAD1-NCOA2 in 2 and SRF-NCOA2 in 1. All fusion-positive congenital/infantile SRMS patients with available long-term follow-up were alive and well, none developing distant metastases. Among the remaining 15 SRMS patients older than 1 year, 10 (67%) showed MYOD1 L122R mutations, most of them following a fatal outcome despite an aggressive multimodality treatment. All 4 cases harboring coexisting MYOD1/PIK3CA mutations shared sclerosing morphology. All 5 fusion/mutation-negative SRMS cases presented as intra-abdominal or paratesticular lesions.

The Evolution of Pediatric Soft Tissue Sarcoma Classification in the Last 50 Years

This review discusses the history of the classification of soft tissue sarcomas in children and adolescents, the current transition toward integration of morphology and molecular genetics as new entities emerge, and future perspectives.

"Sclerosing" Pelvic Floor Rhabdomyoma

PURPOSE

This article reports on a sclerosing perineal-perianal rhabdomyoma in an adult woman. A review of the literature disclosed no reference to this histological form of rhabdomyoma in women.

METHODS AND RESULTS

We describe the case of a 48-year-old woman. At physical examination, a firm nodular lesion was identified in the left lateral perianal-perineal region. Histologically, it comprised rounded and elongated muscle fibers displaying no evident atypia, within a stroma exhibiting marked sclerosis and mild lymphoid infiltrate. At immunohistochemical examination, tumor cells stained for desmin, muscle-specific actin, and myogenin.

CONCLUSIONS

Skeletal muscle rhabdomyomas are rare benign tumors, generally divided into 3 major categories depending on their clinical and morphological characteristics: fetal, adult, and genital. An unusual histological variant of the genital form has recently been reported in men, characterized by the presence of predominantly mature muscle fibers and marked sclerosis. We document such a lesion in a female patient for the first time.

A Rare Pediatric Example of Subcutaneous Extraskeletal Osteosarcoma: A Case Report and Review of the Morphologic Differential Diagnosis

Primary extraskeletal osteosarcoma is an exceedingly rare malignant neoplasm that accounts for approximately 1% of soft tissue sarcomas and most often occurs in the deep soft tissues of adults. Extraskeletal osteosarcoma is characterized by the production of osteoid, bone, and/or chondroid matrix. The diagnosis of extraskeletal osteosarcoma requires careful radiologic and clinical correlation to ensure that the patient does not have an underlying bone primary. This is a case report of primary subcutaneous extraskeletal osteosarcoma arising in the thigh of a 15-year-old girl with a complex karyotype, and the morphologic differential diagnosis is reviewed.

DAX-1 Expression in Pediatric Rhabdomyosarcomas: Another Immunohistochemical Marker Useful in the Diagnosis of Translocation Positive Alveolar Rhabdomyosarcoma

Objectives

The aim of this study was to investigate the expression of DAX-1 in a series of pediatric rhabdomyosarcomas (RMS) with known translocation and compare it to Ap2β, known to be selectively expressed in ARMS.

Design

We revised a series of 71 alveolar rhabdomyosarcomas (ARMS), enrolled in the Italian Protocols RMS 79 and 96, and 23 embryonal rhabdomyosarcomas (ERMS) as controls. Before investigating Ap2β and DAX-1, ARMS were reviewed and reclassified as 48 ARMS and 23 non-ARMS.

Results

Translocation positive ARMS showed a characteristic Ap2β/DAX-1+ staining pattern in 78% of cases, while 76% of classic ERMS were negative for both. Ap2β alone was positive in 3.9% of RMS lacking translocation, whereas DAX-1 alone was positive in 25.4%. Conversely, 9% and 6% of translocation positive ARMS were positive only for DAX-1 or Ap2β, respectively. The 23 non-ARMS shared the same phenotype as ERMS but had a higher frequency of DAX-1 expression.

Conclusions

DAX-1 is less specific than Ap2β, however it is a sensitive marker for translocation positive ARMS and can be helpful in their diagnosis if used in combination with Ap2β.

Clinicopathologic analysis of spindle cell/sclerosing rhabdomyosarcoma

BACKGROUND

Clinical characteristics and optimal treatment strategies for spindle cell/sclerosing rhabdomyosarcoma (ssRMS) have not been well established because of its rarity.

PROCEDURE

Retrospective re-evaluation of sarcoma specimens (1997-2014) identified 16 ssRMSs (median age 20 years, range 7-39 years). Clinicopathological features, clinical course, and outcome were analyzed.

RESULTS

Primary disease sites were the head and neck (10 cases) and other regions (6 cases). Nine cases were at Intergroup Rhabdomyosarcoma Study preoperative stage 3. The primary tumors were >5 cm in 13 cases. Two patients had lymph node metastases, but none had distant metastases at presentation. At follow-up (median period 39 months, range 4.6-201), seven patients were alive without disease. Among nine patients treated with the vincristine, actinomycin, and cyclophosphamide (VAC) regimen, five responded well, with four surviving free of disease. Among ten patients with recurrent or progressive disease, three experienced local recurrence, four had distant metastases, and three had both. None exhibited bone marrow invasion. Eight of the ten patients died in median time from relapse to death of 18 months (range 11-56).

CONCLUSIONS

Although most ssRMSs present as a bulky tumor, nodal or distant metastases are rare at presentation. ssRMSs initially show good response to VAC, but >50% of tumors recur or progress; these data suggest a worse prognosis of ssRMS compared to the pediatric embryonal variant. As relapse typically occurs as local or distant solitary lesion without bone marrow invasion, localized treatment combined with chemotherapy would contribute to improve the prognosis of recurrent ssRMS.

The World Health Organization Classification of Skeletal Muscle Tumors in Pediatric Rhabdomyosarcoma: A Report From the Children's Oncology Group

CONTEXT

The World Health Organization Classification Since 1995, the International Classification of Rhabdomyosarcoma has provided prognostically relevant classification for rhabdomyosarcoma (RMS) and allowed risk stratification for children with RMS. The International Classification of Rhabdomyosarcoma includes botryoid and spindle cell RMS as superior-risk groups, embryonal RMS as an intermediate-risk group, and alveolar RMS as an unfavorable-risk group. The 2013 World Health Organization (WHO) classification of skeletal muscle tumors modified the histologic classification of RMS to include sclerosing RMS as a type of spindle cell RMS separate from embryonal RMS. The current WHO classification includes embryonal, alveolar, spindle cell/sclerosing, and pleomorphic subtypes of RMS and does not separate the botryoid subtype.

OBJECTIVE

To determine if the WHO classification applies to pediatric RMS.

DESIGN

To accomplish this goal, we reviewed 9 consecutive Children's Oncology Group clinical trials to compare the WHO and International Classification of Rhabdomyosarcoma classifications with outcome and site of disease.

RESULTS

Except for a subset of low-risk RMS, the outcome for botryoid was not significantly different from typical embryonal RMS when analyzed by primary site. Similarly, pediatric spindle cell and sclerosing patterns of RMS did not appear significantly different from typical embryonal RMS, with one exception: spindle cell RMS in the parameningeal region had an inferior outcome with 28% event-free survival.

CONCLUSION

Our data support use of the WHO RMS classification in the pediatric population, with the caveat that histologic diagnosis does not necessarily confer the same prognostic information in children as in adults.

Vulvar sarcomas: Short guideline for histopathological recognition and clinical management. Part 1

Malignant tumors of the female reproductive system are a serious health and social problem, as they are the second most common cause of death among women, after breast cancer. Their incidence has increased dramatically during recent years, probably due to the different sexual habits and changes in the prevalence of HIV/ AIDS and HPV virus carriers, among other factors. Vulvar tumors represent only 4% of all gynecological neoplasms, and they are fourth in frequency after tumors of the cervix, uterus, and ovary. Ninety eight percent of all vulvar tumors are benign and only 2% are malignant. The overall incidence of tumors with vulvar location is between two and seven cases per 100,000 women, and it increases with age, while the death rate is estimated at 0.7 per 100,000 women. Sarcomas of the vulva comprise approximately 1-3% of all vulvar cancers, with leiomyosarcomas, epithelioid sarcomas, and rhabdomyosarcomas being the most common among them. They are characterized by rapid growth, high metastatic potential, frequent recurrences, aggressive behavior, and high mortality rate. In this paper, we present the most common forms of sarcomas of the vulva (leiomyosarcoma, epithelioid sarcoma, malignant rhabdoid tumor, rhabdomyosarcoma) in order to emphasize the broad differential diagnosis, rare appearance, non-specific clinical picture, aggressive course, and high mortality.

Needle biopsy of mesenchymal lesions of the head and neck: Evolving concepts and new strategies for diagnosis

Sarcomas are a rare and heterogeneous group of neoplasms that can be a significant diagnostic challenge in routine practice. Recent advances in the understanding of molecular mechanisms underlying oncogenesis have led to an array of novel diagnostic tools. Here we review several sarcomas of the head and neck region, focusing on neoplasms with new molecular findings and highlighting novel diagnostic tools.

WHO classification of soft tissue tumours: an update based on the 2013 (4th) edition

The fourth edition of the World Health Organization (WHO) Classification of Tumours of Soft Tissue and Bone was published in February 2013, and serves to provide an updated classification scheme and reproducible diagnostic criteria for pathologists. Given the relative rarity of soft tissue tumours and the rapid rate of immunohistochemical and genetic/molecular developments (not infrequently facilitating recognition of new tumour entities), this updated text edited by a consensus group is important for both practising pathologists and oncologists. The 2013 WHO classification includes several changes in soft tissue tumour classification, including several new entities (e.g., pseudomyogenic haemangioendothelioma, haemosiderotic fibrolipomatous tumour, and acral fibromyxoma), three newly included sections for gastrointestinal stromal tumours, nerve sheath tumours, and undifferentiated/unclassified soft tissue tumours, respectively, various 'reclassified' tumours, and a plethora of new genetic and molecular data for established tumour types that facilitate better definition and are useful as diagnostic tools. This article briefly outlines these updates based on the 2013 WHO classification of soft tissue tumours.

Recurrent MYOD1 mutations in pediatric and adult sclerosing and spindle cell rhabdomyosarcomas: evidence for a common pathogenesis

Sclerosing and spindle cell rhabdomyosarcoma (RMS) are rare types of RMS recently reclassified as a stand-alone pathologic entity, separate from embryonal RMS (ERMS). Although sclerosing and spindle cell RMS share clinical and morphologic features, a pathogenetic link based on shared molecular alterations has not been established. Spindle cell RMS in children have been associated with a less aggressive clinical course compared to adults. Recently, recurrent MYOD1 mutations were described in 44% of adult spindle cell RMS, but no pediatric tumors or sclerosing RMS were studied for comparison. Thus, we investigated 16 RMS (5 sclerosing and 11 spindle cell) in children and adults for the presence of MYOD1 mutations by targeted Polymerase Chain Reaction (PCR). Remarkably, all 5 sclerosing RMS and 4 of 11 spindle cell RMS showed the MYOD1 p.L122R hot-spot mutation. Of the five pediatric tumors, 2/2 sclerosing RMS and 2/3 spindle cell RMS showed MYOD1 mutations. Three of nine MYOD1-mutant RMS showed coexistent PIK3CA mutations, while no MDM2 amplifications were identified. All four pediatric MYOD1-mutated RMS patients died of the disease at 12-35 months following diagnosis. In conclusion, spindle cell and sclerosing RMS show recurrent MYOD1 mutations, in keeping with a single pathologic entity, regardless of age at presentation. This group however, is distinct from the infantile RMS associated with NCOA2 fusions. Although our study suggests that pediatric MYOD1-mutant RMS follow an aggressive behavior with high mortality, further studies are required to confirm this finding.

CD99 is upregulated in placenta and astrocytomas with a differential subcellular distribution according to the malignancy stage

In the present study, we searched for genes highly expressed in placenta and that could contribute to the establishment and maintenance of a malignant phenotype in different types of tumours, and in astrocytomas in particular. We employed a strategy based on the integration of in silico data from previously generated massively parallel signature sequencing and public serial analysis of gene expression databases. Among 12 selected genes, CD99 exhibited the highest relative mRNA expression in GBM compared to non-neoplastic brain tissues. In a larger cohort of astrocytic tumours, we further demonstrated increased CD99 expression in all malignant grades, with GBMs showing the highest values. These findings were confirmed at the protein level by Western blotting and immunohistochemistry. Additionally, we demonstrated the CD99 localisation profile in astrocytic tumours. Interestingly, CD99 expression was confined to the cytoplasm or membrane in more malignant astrocytomas, in contrast to non-neoplastic brain tissue or non-infiltrative pilocytic astrocytoma, which showed no obvious staining in these structures. Comparison of three GBM cell lines revealed higher CD99 expression at the membrane and higher migratory capacity in the A172 and U87MG lines, but lower CD99 expression and no migratory ability in the T98 line. Knocking down CD99 expression by siRNA decreased significantly the migration of both cell lines. These integrated CD99 gene and protein expression results suggest that CD99 expression in astrocytomas of different malignant grades might contribute to the infiltrative ability and support the importance of CD99 as a potential target to reduce infiltrative astrocytoma capacity in migration and invasion.