Rhabdoid tumors of soft tissues: a clinicopathologic study of 26 cases enrolled on the Intergroup Rhabdomyosarcoma Study

Mediastinal malignant rhabdoid tumor in an infant: A rare case report

Mediastinal malignant rhabdoid tumor (MRT) is an exceedingly rare and aggressive neoplasm, particularly uncommon in infants. We present the case of a previously healthy 7-month-old male infant with mediastinal MRT. The patient initially presented with left eyelid ptosis and was otherwise asymptomatic. Initial investigations, including brain MRI, yielded unremarkable results, and the infant was discharged with vitamin B supplements. However, he was readmitted a week later with prolonged fever, poor feeding, diarrhea, and respiratory distress. Despite an initial diagnosis of bronchiolitis/viral respiratory tract infection, the patient's condition rapidly deteriorated. Subsequent evaluation revealed mediastinal MRT as the underlying cause. This case underscores the diagnostic challenges associated with mediastinal MRT in infants and highlights the importance of considering rare neoplastic etiologies in atypical clinical presentations.

Targeting epigenetic aberrations of sarcoma in CRISPR era

Sarcomas are rare malignancies that exhibit diverse biological, genetic, morphological, and clinical characteristics. Genetic alterations, such as gene fusions, mutations in transcriptional machinery components, histones, and DNA methylation regulatory molecules, play an essential role in sarcomagenesis. These mutations induce and/or cooperate with specific epigenetic aberrations required for the growth and maintenance of sarcomas. Appropriate mouse models have been developed to clarify the significance of genetic and epigenetic interactions in sarcomas. Studies using the mouse models for human sarcomas have demonstrated major advances in our understanding the developmental processes as well as tumor microenvironment of sarcomas. Recent technological progresses in epigenome editing will not only improve the studies using animal models but also provide a direct clue for epigenetic therapies. In this manuscript, we review important epigenetic aberrations in sarcomas and their representative mouse models, current methods of epigenetic editing using CRISPR/dCas9 systems, and potential applications in sarcoma studies and therapeutics.

Loss of Primary Cilia Potentiates BRAF/MAPK Pathway Activation in Rhabdoid Colorectal Carcinoma: A Series of 21 Cases Showing Ciliary Rootlet CoiledCoil (CROCC) Alterations

A rhabdoid colorectal tumor (RCT) is a rare cancer with aggressive clinical behavior. Recently, it has been recognized as a distinct disease entity, characterized by genetic alterations in the SMARCB1 and Ciliary Rootlet Coiled-Coil (CROCC). We here investigate the genetic and immunophenotypic profiling of 21 RCTs using immunohistochemistry and next-generation sequencing. Mismatch repair-deficient phenotypes were identified in 60% of RCTs. Similarly, a large proportion of cancers exhibited the combined marker phenotype (CK7-/CK20-/CDX2-) not common to classical adenocarcinoma variants. More than 70% of cases displayed aberrant activation of the mitogen-activated protein kinase (MAPK) pathway with mutations prevalently in BRAF V600E. SMARCB1/INI1 expression was normal in a large majority of lesions. In contrast, ciliogenic markers including CROCC and γ-tubulin were globally altered in tumors. Notably, CROCC and γ-tubulin were observed to colocalize in large cilia found on cancer tissues but not in normal controls. Taken together, our findings indicate that primary ciliogenesis and MAPK pathway activation contribute to the aggressiveness of RCTs and, therefore, may constitute a novel therapeutic target.

Intraperitoneal rhabdoid tumor with spontaneous internal bleeding in a 9-year-old child: A rare case report

INTRODUCTION AND IMPORTANCE

Malignant rhabdoid tumor is a rare malignancy which occurs in children with limited cases reported.

CASE PRESENTATION

We report a very rare primary intraperitoneal rhabdoid tumor in a 9-year-old female child. The only case was first reported in a 10-year old girl in 2014 (Nam et al., 2014 [1]). The diagnostic became a problem as the case was initially diagnosed as Ovarian Malignancy. It did not match the initial abdominal Computed Tomography (CT) imaging which showed a bilateral malignant ovarian tumor that resembled Ovarian Carcinoma.

CLINICAL DISCUSSION

Preoperative diagnosis of intraperitoneal Rhabdoid tumor is difficult, as it commonly occurs in the brain (ATRT) or Kidney (MRTK) and rarely occurs intraperitoneally. Moreover, the clinical symptom and radiologic findings in this tumor remained unclear. Most cases had CT Scan findings as heterogenous enhancing nodules with central necrosis (hypodense) and usually metastatic. The definitive diagnosis of Rhabdoid Tumor is based on post-resection histopathology and immunohistochemistry (IHC).

CONCLUSION

The intraperitoneal rhabdoid tumor is rare and has an extremely poor prognosis. The physicians should be alert when finding intraabdominal mass; rhabdoid tumor should be the differential diagnosis.

Update of pediatric soft tissue tumors with review of conventional MRI appearance-part 2: vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas

There are numerous soft tissue tumors and tumor-like conditions in the pediatric population. Magnetic resonance imaging is the most useful modality for imaging these lesions. Although certain soft tissue lesions exhibit magnetic resonance features characteristic of a specific diagnosis, most lesions are indeterminate, and a biopsy is necessary for diagnosis. We provide a detailed update of soft tissue tumors and tumor-like conditions that occur in the pediatric population, emphasizing each lesion's conventional magnetic resonance imaging appearance, using the recently released 5^th edition of the World Health Organization Classification of Soft Tissue and Bone Tumors as a guide. In part one of this review, pediatric tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors are discussed. In part two, vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas are reviewed. Per the convention of the WHO, these lesions involve the connective, subcutaneous, and other non-parenchymatous organ soft tissues, as well as the peripheral and autonomic nervous system.

A Role for SMARCB1 in Synovial Sarcomagenesis Reveals That SS18-SSX Induces Canonical BAF Destruction

Reduced protein levels of SMARCB1 (also known as BAF47, INI1, SNF5) have long been observed in synovial sarcoma. Here, we show that combined Smarcb1 genetic loss with SS18-SSX expression in mice synergized to produce aggressive tumors with histomorphology, transcriptomes, and genome-wide BAF-family complex distributions distinct from SS18-SSX alone, indicating a defining role for SMARCB1 in synovial sarcoma. Smarcb1 silencing alone in mesenchyme modeled epithelioid sarcomagenesis. In mouse and human synovial sarcoma cells, SMARCB1 was identified within PBAF and canonical BAF (CBAF) complexes, coincorporated with SS18-SSX in the latter. Recombinant expression of CBAF components in human cells reconstituted CBAF subcomplexes that contained equal levels of SMARCB1 regardless of SS18 or SS18-SSX inclusion. In vivo, SS18-SSX expression led to whole-complex CBAF degradation, rendering increases in the relative prevalence of other BAF-family subtypes, PBAF and GBAF complexes, over time. Thus, SS18-SSX alters BAF subtypes levels/balance and genome distribution, driving synovial sarcomagenesis. SIGNIFICANCE: The protein level of BAF component SMARCB1 is reduced in synovial sarcoma but plays a defining role, incorporating into PBAF and SS18-SSX-containing canonical BAF complexes. Reduced levels of SMARCB1 derive from whole-complex degradation of canonical BAF driven by SS18-SSX, with relative increases in the abundance of other BAF-family subtypes.See related commentary by Maxwell and Hargreaves, p. 2375.This article is highlighted in the In This Issue feature, p. 2355.

Case Analysis of 14 Children with Malignant Rhabdoid Tumor of the Kidney

Objective

This study aims to summarize the clinical features and prognoses of the malignant rhabdoid tumor of the kidney (MRTK) in children. It further aims to analyze the high-risk factors affecting MRTK prognosis.

Methods

Clinical data from 14 children with MRTK treated in Paediatrics of Beijing Tongren Hospital from January 2010 to December 2019, along with the high-risk factors affecting prognosis, were retrospectively analyzed.

Results

There were 14 children with MRTK included in the study, with a median onset age of 13 (3–46) months. Thirteen patients had distant metastases, the most common site for metastases being inside the lung. A comprehensive treatment protocol combined with chemotherapy was mainly applied during the surgery. A surgical resection of primary tumors was performed on 13 (13/14) patients, and all 14 children received chemotherapy with ifosfamide + carboplatin + etoposide, ifosfamide + etoposide, and vincristine + pirarubicin + cyclophosphamide regimens, alternately. Three patients received radiotherapy and two received oral targeted drugs after partial response. The median follow-up was after 16.5 months (3–53 months) and the four-year overall survival (OS) was 41.8%. In children aged ≤24 months and children aged >24 months, the two-year OS was 67.2% and 100% (χ² = 108.998, P<0.05), respectively. In children with Ki 67 > 70% and children with Ki 67 < 70%, the two-year OS was 52.6% and 86.9% (χ² = 8.544, P = 0.003), respectively. In children with distant metastases and children without distant metastasis, the two-year OS was 70% and 100% (χ² = 14.239, P<0.05), respectively.

Conclusion

The most common MRTK distant metastasis site is the lung. Risk factors for poor MRTK prognoses include an age of <24 months, Ki 67 > 70%, and distant metastases.

INI1-negative colorectal undifferentiated carcinoma with rhabdoid features and postoperative rapidly growing liver metastases: a case report and review of the literature

BACKGROUND

Malignant tumors with rhabdoid features are extremely rare. They can occur in various organs, including the gastrointestinal tract, with common clinical features of high malignancy and poor prognosis.

CASE PRESENTATION

A 41-year-old man visited our hospital complaining of lower abdominal pain and fever. Computed tomography (CT) revealed two wall-thickening lesions in the rectum and sigmoid colon, with the latter invading the small intestine and abdominal wall. Lymph nodes were swollen in the sigmoid mesocolon and at the roots of the inferior mesenteric artery. Colonoscopy revealed a circular type 3 lesion in the sigmoid colon and a semicircular type 2 lesion in the rectum. Biopsies of the sigmoid colon and rectum lesions revealed poorly and moderately differentiated adenocarcinoma cells, respectively. The sigmoid colon, rectum, invaded small intestine, and abdominal wall were resected; lymph node dissection was also performed. Histopathological finding of the sigmoid colon lesion revealed that the tumor cells had poor connectivity with each other, and each cell had eosinophilic cytoplasm and a polymorphic nucleus. These characteristics are termed rhabdoid features, because the morphology of these cells is similar to that of rhabdomyosarcoma tumor cells. Immunohistochemical examination showed that the tumor cells were positive for both epithelial (cytokeratin AE1/AE3) and mesenchymal cell markers (vimentin); however, they were negative for integrase interactor 1 (INI1). Therefore, the sigmoid colorectal cancer was diagnosed as an INI1-negative undifferentiated carcinoma with rhabdoid features. The patient continued to experience high fever after surgery; thus, we performed an abdominal CT scan that revealed cystic lesions in the liver 4 days after surgery. These were absent in the positron emission tomography (PET)-CT scan performed 14 days before surgery. These tumors grew rapidly, and fine needle aspiration cytology revealed that they were undifferentiated carcinomas compatible with metastatic lesions from the undifferentiated carcinoma with rhabdoid features from the sigmoid colon. Chemotherapy was administered but was not effective. The patient died 60 days after surgery.

CONCLUSIONS

INI1-negative colorectal undifferentiated carcinomas with rhabdoid features are extremely rare, have high histological malignancy, and a poor prognosis. Chemotherapy is not effective. Effective systemic therapy is desired.

SMARCB1-deficient carcinomas of the head and neck region: a cytopathologic characterization

INTRODUCTION

SMARCB1 encodes for a component of the SWI/SNF complex and is widely implicated in carcinogenesis. In the head and neck, SMARCB1-deficient carcinomas typically arise in the sinonasal tract but can be found at other sites. EZH2 inhibitors have emerged as potential targeted therapy against SWI/SNF-deficient tumors. We sought to characterize the cytomorphology of head and neck carcinomas with SMARCB1 deficiencies to identify potential candidates for targeted therapy.

MATERIALS AND METHODS

Head and neck carcinomas with SMARCB1 mutations were retrospectively identified and confirmed to be SMARCB1-deficient by both molecular (fluorescent in-situ hybridization or next generation sequencing) and immunohistochemical means. Cases with positive cytology were reviewed and their cytologic features cataloged.

RESULTS

A total of 19 specimens from 13 patients were reviewed, including 8 specimens from 7 sinonasal carcinomas, 4 specimens from 3 thyroid carcinomas, 3 specimens from 2 skin carcinomas, and 4 specimens from 1 carcinoma of unknown primary origin. High-grade features were common, including mitoses (11 of 19) necrosis (13 of 19) and multinucleation (16 of 19). Tumors showed either dense cytoplasm with distinct cell borders (10 of 19) or delicate cytoplasm with indistinct cell borders (9 of 19). Most tumors showed no distinct epithelial differentiation (12 of 19), while some (7 of 19) showed glandular or signet ring features. A minor cohort demonstrated rhabdoid cells (4 of 19).

CONCLUSIONS

Head and neck carcinomas with SMARCB1 deficiencies have a wide array of morphologies and tend to demonstrate high-grade features. Only a minor cohort demonstrate rhabdoid-type cells. Evaluation of SMARCB1 deficiency for potential targeted therapy should not be limited to tumors with rhabdoid morphology.

Small cell carcinoma of the ovary hypercalcemic type (SCCOHT): Comprehensive management of a newly diagnosed young adult

SCCOHT is an aggressive malignancy linked to alterations of SMARCA4. We describe the diagnosis and therapy of a 32 year old who received multi-agent chemotherapy and underwent a second look operation with HIPEC followed by high-dose chemotherapy with stem cell transplant. Supportive care, oncofertility, and genetic counseling are described.

SWI/SNF complex-deficient soft tissue neoplasms: An update

The SWItch Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex is a large multi-subunit protein assembly that orchestrates chromatin compaction and accessibility for gene transcription in an ATP-dependent manner. As a key epigenetic regulator, the SWI/SNF complex coordinates gene expression, cell proliferation and differentiation, and its biologic functions, in part, antagonize the polycomb repressive complex 2. The mammalian SWI/SNF complex consists of 15 subunits encoded by 29 genes, some of which are recurrently mutated in human cancers, in the germline or sporadic setting. Most SWI/SNF-deficient tumors share common "rhabdoid" cytomorphology. SMARCB1 (INI1) is the subunit most frequently inactivated in soft tissue neoplasms. Specifically, SMARCB1 deficiency is observed as the genetic hallmark in virtually all malignant rhabdoid tumors, and most cases of epithelioid sarcoma and poorly differentiated chordoma. In addition, subsets of myoepithelial carcinoma (10-40%), extraskeletal myxoid chondrosarcoma (20%), epithelioid schwannoma (40%), and epithelioid malignant peripheral nerve sheath tumor (70%) demonstrate SMARCB1 loss. The gene encoding the SS18 subunit is involved in the SS18-SSX rearrangement, which is pathognomonic of synovial sarcoma and indirectly inactivates SMARCB1. Finally, undifferentiated SMARCA4-deficient thoracic sarcomas are defined by SMARCA4 subunit inactivation, leading to SMARCA4 and SMARCA2 loss. Rarely, inactivation of alternate but biologically equivalent key regulators can substitute for canonical subunit deficiency, such as SMARCA4 inactivation in cases of SMARCB1-retained epithelioid sarcoma. This review briefly highlights SWI/SNF complex biologic functions and its roles in human cancer and provides a detailed update on recent advances in soft tissue neoplasms with canonical SWI/SNF complex deficiency, correlating morphologic, genomic, and immunohistochemical findings.

Intradural lumbosacral malignant extrarenal rhabdoid tumor: a case report

BACKGROUND

Rhabdoid tumors are highly malignant tumors predominantly affecting the pediatric population. When these tumors occur outside of the kidneys, they are referred to as malignant extrarenal rhabdoid tumors (MERT), a rare highly aggressive subtype. Less commonly, these tumors involve the neuro-axis.

OBJECTIVE

Here we present a case of a 15-year-old girl with intradural MERT of the lumbosacral spine who presented with back pain, sudden worsening of lower extremity strength, and complete loss of bowel and bladder control.

RESULTS

The patient's tumor showed loss of INI-1 and negative staining for cytokeratin AE1AE3, CD99, and SOX10.

CONCLUSIONS

To our knowledge, there are no previous case reports of MERT with intradural lumbosacral spinal involvement.

Neck Rhabdoid Tumors: Clinical Features and Consideration of Autologous Stem Cell Transplant

Extrarenal malignant rhabdoid tumors (MRT) have a poor prognosis despite aggressive therapy. Adding high-dose chemotherapy with autologous stem cell rescue (HDC-ASCR) as consolidative therapy for MRT is controversial. We describe 2 patients, age 13 years and 19 months, with unresectable neck MRT. After chemotherapy and radiotherapy, both underwent HDC-ASCR and remain in remission over 4 years later. We reviewed all published cases of neck MRT, and found poorer outcomes and more variable age of presentation and time to progression than MRT at other sites. Neck MRT may represent a higher-risk subset of MRT, and addition of HDC-ASCR merits consideration.

Diagnosis, Classification, and Management of Soft Tissue Sarcomas

BACKGROUND

Soft tissue sarcomas are challenging to oncologists due to their unique character, the infrequency of their occurrence, and the difficulties in predicting outcomes. Advances in imaging, as well as improvements in surgical techniques and adjunctive treatment methods, have improved care for patients with these unusual disorders.

METHODS

The various types of soft tissue tumors are defined, and the statistics for the Orthopaedic Oncology Group in relation to them are reviewed and compared with literature references.

RESULTS

The overall survival rate for 1,220 tumors treated at our institute from June 1972 to June of 2001 was 72%, with a wide range. Patients with leiomyosarcomas, clear cell sarcomas, and malignant fibrous histiocytomas had a poorer survival rate, while those with fibrosarcomas, liposarcomas, and neurofibrosarcomas fared better. Outcome was affected by patient age, tumor anatomic site, tumor stage, and a history of recurrence.

CONCLUSIONS

Competent imaging, predictive immunological and genetic studies, improved surgery, and newer methods of adjunctive and neoadjunctive treatment should result in improvements in outcomes for patients with these tumors.

Recurrent BCOR internal tandem duplication and BCOR or BCL6 expression distinguish primitive myxoid mesenchymal tumor of infancy from congenital infantile fibrosarcoma

Primitive myxoid mesenchymal tumor of infancy is a rare sarcoma that preferentially affects infants. It can be locally aggressive and rarely metastasizes, but the long-term outcome of children with this tumor is mostly unknown. Histologically, it is characterized by primitive cells with abundant myxoid stroma. Internal tandem duplication of B-cell CLL/lymphoma 6 (BCL6)-interacting co-repressor (BCOR) exon 15 has recently been described in clear cell sarcoma of kidney, central nervous system high-grade neuroepithelial tumor with BCOR alteration, and primitive myxoid mesenchymal tumor of infancy. Herein, we report five cases of primitive myxoid mesenchymal tumor of infancy: three girls and two boys with mean age of 6.5 months. The tumors were located in the paraspinal region (n=3), back (n=1), or foot (n=1) and ranged in size from 2.5 to 10.2 cm. BCOR internal tandem duplication was confirmed by PCR and sequencing in all five cases. The minimally duplicated region consisted of nine residues, which is shorter than was previously reported in other BCOR-associated tumors. To assess the clinical value and specificity of the BCOR internal tandem duplication, a group of 11 ETV6-rearranged congenital infantile fibrosarcomas were evaluated and no BCOR internal tandem duplication was identified in any case. Though not detected in congenital infantile fibrosarcomas, BCOR and BCL6 immunoreactivity was present in >90% of the nuclei of tumor cells in each of the five primitive myxoid mesenchymal tumor of infancy. The presence of BCOR internal tandem duplication in all five primitive myxoid mesenchymal tumors of infancy provides evidence that it is a recurrent somatic abnormality and substantiates the concept that this tumor is a unique sarcoma of infancy. Our findings indicate that identification of BCOR internal tandem duplication and/or nuclear immunoreactivity for BCOR or BCL6 can aid in the diagnosis of primitive myxoid mesenchymal tumor of infancy and help to differentiate it from congenital infantile fibrosarcoma.

Rhabdoid Myomelanocytic Tumor (PEComa) of the Ovary

A 3.0 × 2.5 cm rhabdoid myomelanocytic tumor was incidentally found in the left ovary of a 43-year-old black woman. The tumor cells were cytologically bland with minimal proliferation rate, multifocally weakly or moderately expressed TFE3, strongly expressed smooth muscle markers and SMARCB1/INI1, and focally expressed HMB45. They contained numerous paranuclear whorls of intermediate filaments that were verified by ultrastructure. No other lines of differentiation were detected within the tumor. Neither translocation nor increased number of copies of the TFE3 gene at Xp11.22 was detected by fluorescence in situ hybridization. The patient remains well, free of tumor, 7 years after surgery. A rhabdoid variant of myomelanocytic tumor is a rarity, with only a single case described previously.

Epithelioid Sarcoma: Diagnostic Features and Genetics

Epithelioid sarcoma (ES) is a rare, aggressive soft-tissue neoplasm of uncertain differentiation, characterized by nodular aggregates of epithelioid cells, which are immunoreactive to cytokeratins (CKs) and epithelial membrane antigen, and often for CD34. It has a propensity for multifocal disease at presentation, local recurrence, and regional metastasis. These are aggressive neoplasms with particularly poor prognosis after regional or distant metastatic disease, for which surgical resection is still the mainstay of treatment, and options for patients with metastatic disease remain undefined. There are 2 distinct variants: classic ES, which typically presents as a subcutaneous or deep dermal mass in the distal extremities of young adults and comprises nodular distributions of relatively uniform epithelioid cells with central necrosis, and the proximal variant, which has a predilection for proximal limbs and limb girdles and the midline of the trunk, which is composed of sheets of larger, more atypical cells with variable rhabdoid morphology. Both classic and proximal-type ESs are associated with the loss of SMARCB1/INI1 protein expression, but appear otherwise molecularly relatively heterogeneous. We review classic and proximal-type ES, discussing morphology, immunohistochemical and genetic findings, the differential diagnosis, and the future potential for targeted therapies.

Angiomatoid fibrous histiocytoma: the current status of pathology and genetics

CONTEXT

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue neoplasm of intermediate biologic potential and uncertain differentiation, most often arising in the superficial extremities of children and young adults. While it has characteristic histologic features of nodular distributions of ovoid and spindle cells with blood-filled cystic cavities and a surrounding dense lymphoplasmacytic infiltrate, there is a significant morphologic spectrum, which coupled with its rarity and lack of specific immunoprofile can make diagnosis challenging. Angiomatoid fibrous histiocytoma is associated with 3 characteristic gene fusions, EWSR1-CREB1 and EWSR1-ATF1, which are also described in other neoplasms, and rarely FUS-ATF1. Angiomatoid fibrous histiocytoma is now recognized at an increasing number of sites and is known to display a variety of unusual histologic features.

OBJECTIVE

To review the current status of AFH, discussing putative etiology, histopathology with variant morphology and differential diagnosis, and current genetics, including overlap with other tumors harboring EWSR1-CREB1 and EWSR1-ATF1 fusions.

DATA SOURCES

Review of published literature, including case series, case reports, and review articles, in online medical databases.

CONCLUSIONS

The occurrence of AFH at several unusual anatomic sites and its spectrum of morphologic patterns can result in significant diagnostic difficulty, and correct diagnosis is particularly important because of its small risk of metastasis and death. This highlights the importance of diagnostic recognition, ancillary molecular genetic confirmation, and close clinical follow-up of patients with AFH. Further insight into the genetic and epigenetic changes arising secondary to the characteristic gene fusions of AFH will be integral to understanding its tumorigenic mechanisms.

Poorly differentiated cecal adenocarcinoma showing prominent rhabdoid feature combined with appendiceal mucinous cystadenoma: A case report and review of the literature

Extrarenal rhabdoid tumors (ERRTs) are extremely rare neoplasms; of these, colorectal ERRTs are the most rare, and only nine cases have been previously described in the English language literature. The current study reports the pathological features of a case of poorly differentiated cecal adenocarcinoma with prominent rhabdoid feature, which was combined with mucinous cystadenoma of the appendix in a 73-year-old male, and additionally reviews the previously reported cases. Microscopically, the majority of tumor cells were non-cohesive or loosely cohesive, with a polygonal morphology and prominent rhabdoid feature, showing eccentric vesicular nuclei, prominent nucleoli and abundant eosinophilic cytoplasm. Immunohistochemically, the tumor cells were positive for cytokeratin (CK) and vimentin, but negative for CK20, CK7, desmin and smooth muscle actin. This indicated a diagnosis of poorly differentiated adenocarcinoma with prominent rhabdoid features, combined with appendiceal mucinous cystadenoma. At two months following surgery the patient succumbed to peritoneal seeding and metastasis of liver and bone The emergence of the rhabdoid phenotype is invariably associated with an aggressive and almost always fatal clinical course. The present case is the 10th example of such a tumor in the colon, and to the best of our knowledge, this is the first case of colonic rhabdoid tumor coinciding with appendiceal benign mucinous neoplasm.

Myoepithelial tumor of soft tissue: histology and genetics of an evolving entity

Myoepithelial neoplasms represent a heterogeneous group of tumors of which classification is incomplete and evolving. Those of the soft tissues often form genetically distinct subgroups that differ from those arising within salivary glands. Soft-tissue myoepithelial tumors (including mixed tumors that show true glandular or ductal differentiation) exhibit a spectrum of different morphologic patterns, making them difficult to distinguish from a variety of other neoplasms. They have been increasingly shown to harbor genetic fusions involving EWSR1 and partner genes that are not seen in the well-characterized tumor classes involving EWSR1 translocations. We review the spectrum of soft-tissue myoepithelial tumors, discussing recent immunohistochemical and genetic findings and the differential diagnosis.

Malignant rhabdoid tumor of the tongue: A rare occurrence

Malignant rhabdoid tumors (MRTs) are highly aggressive neoplasms that most commonly occur in the kidneys of young children. Malignant rhabdoid tumor of the tongue is an extremely rare entity and very few have been reported in the literature. The course of extra-renal MRT is short and its prognosis is very poor. A 19-year-old female presented with a progressive swelling and restricted mobility of the tongue for over 3 months duration. We present here a locally advanced case of MRT of the tongue, its diagnosis, management and review of the literature related to it.

Pathology and diagnosis of SMARCB1-deficient tumors

Malignant rhabdoid tumor (MRT) can occur in the kidney, central nervous system, or extracranial/extrarenal locations and is characterized by alterations in the SMARCB1 gene. The tumors occur in infants and young children and confer a poor prognosis requiring aggressive therapeutic interventions to improve the chances for survival. MRTs pose a diagnostic challenge, as they display heterogeneous histopathologic features and differentiate along multiple lineages. The identification of alterations in the SMARCB1 gene in MRT using immunohistochemical (IHC) staining has lead to improved diagnosis of MRT as well as the discovery of the loss of SMARCB1 expression in some non-MRTs. Whether loss of SMARCB1 plays a pathogenic role in nonrhabdoid tumors remains to be determined; however, most of these tumors lack the clinical and other molecular features of MRT. We review the histopathologic features of MRT and the importance and significance of loss of expression of SMARCB1 in both MRT and nonrhabdoid tumors.

Rhabdoid Variant of Myoepithelial Carcinoma, with EWSR1 Rearrangement: Expanding the Spectrum of EWSR1-Rearranged Myoepithelial Tumors

Myoepithelial and mixed tumors represent a heterogeneous group of neoplasms for which classification is incomplete and continues to evolve. Those arising in the soft tissues appear to represent subgroups that are genetically distinct from those that occur within salivary glands. We describe a case of soft tissue myoepithelial carcinoma with rhabdoid morphology, which presented as an enlarging neck mass in a 40 year old male, and in which EWSR1 rearrangement was demonstrated by fluorescence in situ hybridization. This neoplasm showed diffuse INI1 loss, making distinction from other INI1-negative rhabdoid tumors difficult. This expands the range of reported histologic features of EWSR1-rearranged myoepithelial neoplasms, and highlights the significant morphologic and immunohistochemical overlap between this and other INI1-negative malignant rhabdoid neoplasms.

Malignant rhabdoid tumor of the liver presented with initial tumor rupture

Malignant rhabdoid tumor (MRT) of the liver is a rare, highly aggressive tumor of early childhood. We report a 6-month-old boy who was diagnosed with MRT of the liver and presented with spontaneous tumor rupture. The patient underwent intensified chemotherapy and a radical surgical procedure. Twenty four months from the time of the diagnosis, he is alive without evidence of disease. This is the second report of prolonged survival after initial rupture of hepatic MRT.

New concepts for the treatment of pediatric nonrhabdomyosarcoma soft tissue sarcomas

Nonrhabdomyosarcoma soft tissue sarcomas form a group of rare tumors with a different biology and clinical behavior. The recently established European Pediatric Soft Tissue Sarcoma Study Group is organizing a new study devoted specifically to these tumors that were formerly treated according to the principles derived from experience with rhabdomyosarcoma, which is a clearly distinct entity. The new study includes two prospective trials, one for synovial sarcoma and the other for adult-type nonrhabdomyosarcoma soft tissue sarcomas. While surgery remains the mainstay of treatment, the role of adjuvant therapy is not yet clear and our understanding of the biology and natural history of nonrhabdomyosarcoma soft tissue sarcomas is still incomplete. This review presents the latest data on nonrhabdomyosarcoma soft tissue sarcoma treatment and outcome, and the rationale behind a risk-adapted treatment program that investigates the role of full-dose ifosfamide-doxorubicin chemotherapy in improving the response rate of patients with unresectable disease, the chances of avoiding adjuvant chemotherapy in low-risk synovial sarcomas, and the possible role of chemotherapy in high-risk adult-type soft tissue sarcomas.

Rhabdoid tumors: clinical approaches and molecular targets for innovative therapy

Rhabdoid tumors are rare but highly aggressive tumors with a predilection for infants and young children. The majority of these tumors harbor biallelic mutations in SMARCB1/INI1/hSNF5. Rather rare cases with mutations in other SWI/SNF core members such as BRG1 are on record. Rhabdoid tumors have only recently been registered and treated according to specifically designed treatment recommendations and in the framework of clinical trials. Within the last decade, prognosis has improved significantly but at least 50% of patients still relapse and subsequently almost inevitably succumb to their disease. This review summarizes past and current clinical approaches and presents an overview of the rationales for targeted therapy with potential for future clinical treatment trials for rhabdoid tumors.

Cutaneous malignant rhabdoid tumor in the palm of an adult

Malignant rhabdoid tumor is a rare tumor occurring mostly in the neonatal kidneys and central nervous system. Cutaneous malignant rhabdoid tumors are extremely rare in adults. The aim of the study was to report on the clinical, histologic, and immunophenotypic characteristics of this cutaneous malignant rhabdoid tumor which developed in an adult. A 27-year-old male complained of a right palm neoplasm that had been present for 6 months, which was initially diagnosed as an epithelioid sarcoma by biopsy. However, detailed investigation with immunohistochemistry enabled us to make a diagnosis of a rhabdoid tumor. The patient underwent radical abrasion, chemotherapy, and irradiation, and has survived for 1 year without relapse. Only 20 adult cases have been reported thus far in the English literature. We are reporting the 21^st case, who remains disease-free at 12 months. Complete resection and local irradiation may increase survival, because there is no standard and reliable curative chemotherapeutic regimen.

Primary rhabdoid adrenocortical carcinoma: a clinicopathological and immunohistochemical study of three cases

AIMS

We describe three cases of primary adrenocortical carcinoma (ACC) with prominent rhabdoid features and study their clinicopathological and immunohistochemical properties.

METHODS AND RESULTS

The patients were three females aged 45-55 years (mean 49 years), none of whom had any hormone-related symptoms. Histologically, the characteristic features were rhabdoid tumour cells with prominent eosinophilic cytoplasmic inclusions, eccentric vesicular nuclei and prominent nucleoli. Areas of more conventional ACC were present in all cases. Immunohistochemically, the rhabdoid component showed a similar staining pattern to conventional ACC, being positive for steroid receptor cofactor 1, inhibin, melan A, calretinin and synaptophysin, while negative for high molecular weight cytokeratin and Pax8. In addition, antimitochondrial antibodies showed a weak reaction and nuclear expression of integrase interactor 1 (INI1) was preserved. Clinical follow-up information for two patients demonstrated that one patient was alive 237 months after diagnosis, and one patient had died of disease 4 months after diagnosis.

CONCLUSIONS

ACC with rhabdoid features are rare tumours that seem to mirror the clinical and immunohistochemical features of conventional ACC. In addition, they appear to display similar biological behaviour. Adrenocortical carcinoma should be included in the differential diagnosis when evaluating tumours of unknown origin with rhabdoid morphology.

Surgery and actinomycin improve survival in malignant rhabdoid tumor

Purpose. Malignant rhabdoid tumor (MRT) is an uncommon tumor that rarely occurs outside of renal and central nervous system (CNS) sites. Data from the literature were compiled to determine prognostic factors, including both demographic and treatment variables of malignant rhabdoid tumor, focusing on those tumors arising in extra-renal, extra-CNS (ER/EC MRT) sites. Patients and Methods. A systematic review and meta-analysis was performed by extracting demographic, treatment, and survival follow up on 167 cases of primary ER/EC MRT identified in the literature. Results. No survival differences were observed between those treated with or without radiation, or with or without chemotherapy. A Cox regression of overall survival revealed several independent prognostic factors. Surgical excision had a 74% (P = 0.0003) improvement in survival. Actinomycin had a 73% (P = 0.093) improvement in survival. Older age was associated with improved survival. The four-year survival, by Kaplan-Meier estimates, comparing patients less than two years old versus older than two at diagnosis was 11% versus 35%, respectively (P = 0.0001, Log-Rank). Conclusion. ER/EC MRT is a rare, soft-tissue tumor with a poor prognosis most commonly occurring in children. Surgical resection, treatment with actinomycin, and older age at diagnosis are all associated with improved survival.

Neonatal soft tissue sarcomas

Soft tissue tumors in very young children pose diagnostic and therapeutic challenges. Vascular tumors are the most prevalent soft tissue neoplasms in the neonatal period. They are generally benign tumors, but may exhibit aggressive behaviour and cause life-threatening complications. Fibroblastic tumors of intermediate prognosis, more prevalent in very young children (especially infantile fibrosarcoma), are locally aggressive. Since metastases are unusual in this group of tumors, complete surgical resection is generally curative. However, these tumors often present a therapeutic challenge because of the location which makes complete surgical resection difficult. Among the malignant soft tissue tumors, rhabdomyosarcoma is most frequent. It is an aggressive high-grade tumor, with local invasiveness and a propensity to metastasize. These tumors respond to chemotherapy and radiotherapy. Neonates with rhabdomyosarcoma seem to have a worse prognosis than in older age groups. This may be a result of inappropriate dosing of chemotherapeutic agents and decreased use of radiation therapy among other factors.

Soft tissue tumors of uncertain origin

Many soft tissue tumors of childhood lack obvious differentiation toward a defined mesenchymal tissue type or have a phenotype that does not correspond to any defined normal tissue. These challenging tumors are currently regarded as neoplasms of uncertain differentiation. Nonetheless, there have been great strides in the understanding of their pathologic and genetic features and biologic underpinnings. The application of new genetic information to the pathologic diagnosis among this group of tumors is an emerging area in diagnostic pediatric pathology. This article reviews the clinicopathologic features of tumors of uncertain and/or miscellaneous origin, with an emphasis on the unique aspects of these neoplasms in children and adolescents, use of diagnostic adjuncts, and differential diagnosis.

Myogenic tumors in children and adolescents

Neoplasms of striated and smooth muscle in children are a diverse group of neoplasms that have some unique aspects in contrast to these tumors in adults. Rhabdomyosarcoma is the most common soft tissue sarcoma of infancy and childhood and is relatively common in adolescents. In contrast, smooth muscle tumors are relatively rare, and the various types of rhabdomyoma and smooth and skeletal muscle hamartomas are very uncommon. In recent years, the understanding of the pathologic and genetic aspects of rhabdomyosarcoma has been enhanced by adjunct techniques, such as immunohistochemistry and cytogenetic or molecular genetic analysis. The current classification of rhabdomyosarcoma emphasizes the histologic-prognostic correlations. This article reviews the clinicopathologic features of striated and smooth muscle tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents and the differential diagnosis.

Downregulation of microRNAs miR-1, -206 and -29 stabilizes PAX3 and CCND2 expression in rhabdomyosarcoma

Elevated levels of PAX3 and cell proliferation genes are characteristic features of rhabdomyosarcoma (RMS). We hypothesize that the increased levels of these genes are stabilized due to downregulation of specific miRNAs. In this study, we show that downregulation of miR-1, -206 and -29 stabilizes the expression of PAX3 and CCND2 in both embryonal (ERMS) and alveolar (ARMS) RMS types. Ectopic expression of miR-1 and 206 in JR1, an ERMS cell line, show significant downregulation of PAX3 protein expression, whereas overexpression of these miRNAs in Rh30, an ARMS cell line, did not show any effect in PAX3 protein levels. In ARMS, PAX3 forms a fusion transcript with FOXO1 and the resultant loss of PAX3 3'UTR in the fusion transcript indicate an oncogenic mechanism to evade miRNA-mediated regulation of PAX3. Further, we show that miR-1, -206 and -29 can regulate the expression of CCND2, a cell cycle gene. In addition to CCND2, miR-29 also targets E2F7, another cell cycle regulator. Cell function analysis shows that overexpression of miR-29 downregulates the expression of these cell cycle genes, induces partial G1 arrest leading to decreased cell proliferation. Taken together our data suggest that the RMS state is stabilized by the deregulation of multiple miRNAs and their target genes, supporting a tumor suppressor role for these miRNA.

INI1-deficient tumors: diagnostic features and molecular genetics

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

Primary vulval rhabdoid tumor in an adult: a case report, immunohistochemical profile and literature review

We report a rare case of primary vulval rhabdoid tumor in an adult. The diagnosis was confirmed using the recently emerging INI1/BAF47 immunostain. We also demonstrate the expression of ER and PR hormonal receptors by the tumor cells.

Large cell lung carcinoma with rhabdoid phenotype: Case report

Large cell carcinoma of the lung with a rhabdoid phenotype is very rare. We report a 62-year-old male patient admitted to our hospital due to chest pains and hemoptysis. The computed tomography scan of the lungs revealed a massive consolidation of the parenchyma in the upper right lobe. The right upper lobectomy and mediastinal lymph node sampling were carried out. The microscopic appearance suggested a large cell carcinoma with a rhabdoid phenotype, with no foci of any other carcinomatous components. The tumor cells had eosinophilic cytoplasmic globules and eccentric nuclei. Immunohistochemically, vimentin was diffusely positive. The epithelial membrane antigen and neuron-specific enolase were focally positive. We expect a good outcome for this patient because the diagnostic procedure and successful operation were performed in the early stage (IA-T1aN0) of the disease.

Extrarenal malignant rhabdoid tumors: radiologic findings with histopathologic correlation

Extrarenal malignant rhabdoid tumors (MRT) are extremely rare. There have been only a few cases of MRT described in the literature and even fewer in the radiology literature. We present rare uterine and hepatic MRT and their computed tomography, magnetic resonance, and ultrasound imaging features with histopathologic correlation. Although the final diagnosis is based largely on histopathology, radiologists should include MRT in their differential considerations, regardless of tumor location, when they are dealing with an extremely aggressive tumor of early childhood.

Extra-renal non-cerebral rhabdoid tumours

BACKGROUND

Rhabdoid tumours (RTs) are aggressive malignancies of childhood, mainly occurring in the kidney and brain. We describe a national multi-centre retrospective analysis of extra-renal non-cranial RTs (ERRTs).

PROCEDURE

Diagnosis relied on central histological review and/or on hSNF5/INI1 defect, evidenced by immunohistochemistry or molecular screening. Clinical data were obtained from physicians.

RESULTS

Twenty six patients fulfilled the inclusion criteria. Median age at diagnosis was 28 months [0-366], including late childhood and young adults cases. Surgery, either initial or secondary, was complete in three. All but three patients received chemotherapy, with variable regimens. Additional radiotherapy was used in six patients. Median time to recurrence or progression was 5 months [0-44], and one patient remained free of disease at 7 years.

CONCLUSIONS

ERRTs share the same chemosensitivity, early recurrence, and poor prognosis as renal and cerebral RTs. No chemotherapy regimen demonstrates a superior response.