Cytologic diagnosis of Ewing sarcoma/peripheral neuroectodermal tumor with paired prospective molecular genetic analysis

The Small Round Cell Sarcomas Complexities and Desmoplastic Presentation

Background

Small round cell sarcomas (SRCSs) account for most solid malignancies in the pediatric age group and are a part of group of malignant tumors characterized by heterogenous clinical presentation and overlapping microscopic features of small, round, primitive cells. In addition to the recently established certain genetically defined subset of undifferentiated round cell sarcomas of soft tissue and bone, this group of sarcomas include desmoplastic small round cell tumor, poorly differentiated synovial sarcoma, alveolar rhabdomyosarcoma, mesenchymal chondrosarcoma, and small cell osteosarcoma. Although, those entities share clinical and cytomorphologic features and cannot be unequivocally classified based on clinical presentation and morphology alone. Most of SRCSs characterizes of particular patterns of protein expression or genetic changes and ancillary tests remain necessary to confirm or rule out a specific diagnosis. Subtle but occasionally distinctive cytologic features narrows the number of differential diagnoses and helps to select appropriate ancillary tests necessary for the final diagnosis. Thus, when adequate fine needle aspiration (FNA) biopsy specimen is combined with ancillary tests, a specific histologic diagnosis can be made in almost all cases. However, due to complex cytologic features of SRCS as well as various quality and diversity of FNA smears, there are cases in that cytologic features which do not entirely match the known diagnostic criteria.

Summary

The aim of this review was to summarize cytomorphologic criteria and to present rare and divergent cytological features of SRCSs. Careful assessment of clinical presentation, cytological features, immunohistochemical patterns, and molecular alternations is necessary for an accurate diagnosis. Knowing of rare and divergent microscopic findings that does not fit with the known cytological criteria will help to avoid misdiagnosis.

Key Messages

The role of FNA biopsies diagnosing soft tissue and bone tumors has been increasing because of the ability of ancillary tests to assist in the diagnosis of specific tumors. SRCSs may be diagnosed accurately in cytology specimens. Access to clinical and radiographic presentation, utility of ancillary tests, understanding complexity of cytological features, and awareness of the rare cytologic findings that differ from that of the established diagnostic criteria are essential to make correct diagnosis.

Cytology of Undifferentiated Round-Cell Sarcomas of Bone and Soft Tissue: Ewing Sarcoma or Not Ewing Sarcoma , That Is the Question

BACKGROUND

Undifferentiated round-cell sarcomas (URCSs) of soft tissue and bone are a group of clinically heterogeneous tumors. Diagnosis of these malignancies is based mainly on recurrent genetic alterations. The most common and the best known representative of this group is Ewing sarcoma (ES) which is characterized by gene fusions including EWSR1 or FUS and ETS transcription factors family. Other newly described entities are CIC-rearranged sarcoma, sarcoma with BCOR genetic alterations, and round-cell sarcoma with EWSR1-non-ETS fusions. All these novel tumors are known as Ewing-like sarcomas.

SUMMARY

It is believed that morphologic features of ES and Ewing-like sarcomas vary only slightly or even that cytomorphology is not relevant. But differences are usually obvious, and some cytologic findings, such as spindle cells, connective tissue fragments, or myxoid stroma, are typical for Ewing-like sarcomas but not for ES. Each of these entities is also characterized by different immunoprofiles. The aim of this review was to summarize cytomorphologic and immunohistochemical features of URCS and compare them with other small round-cell tumors. Key Messages: Cytology can be successfully used in URCS diagnosis as a complementary tool for core-needle biopsy or even alone in selected cases, especially in recurrent and metastatic tumors. Knowing the morphologic and immunohistochemical differences between URCS is essential to provide appropriate ancillary studies and make a definitive diagnosis.

A Review of Effusion Cytomorphology of Small Round Cell Tumors

BACKGROUND

Small round cell tumors (SRCTs) are a broad category of diverse malignant tumors composed of monotonous undifferentiated cells. Involvement of serous fluids by SRCT is rare; however, the identification of exfoliated malignant cells is a crucial component of management and has significant implications for treatment and prognosis. The most common effusion tumors with SRCT morphology include Ewing sarcoma, synovial sarcoma, rhabdomyosarcoma (RMS), small-cell neuroendocrine carcinoma (SCNC), and desmoplastic SRCT, and the cytomorphologic distinction between these tumors is challenging. The purpose of this article is to describe the morphologic features of the most common SRCT in fluids and propose helpful ancillary testing.

SUMMARY

Effusion SRCTs display similar primitive and undifferentiated morphologic features although each has subtle variations. Ewing sarcoma is a mesenchymal neoplasm and harbors characteristic translocations t(11;22) (EWSR1-FLI1) or t(21;22) (EWSR1-ERG). In fluids, Ewing sarcoma shows poorly differentiated cells of variable size with round to oval nuclei, prominent nucleoli, and scant cytoplasm. In contrast, synovial sarcoma typically involves extremities and expresses a fusion transcript in t(X;18) (SS18-SSX). This soft tissue neoplasm demonstrates uniform cells with irregular nuclear contours, characteristic nuclear folding, and scant cytoplasm. RMS is a neoplasm arising from skeletal muscle, and the alveolar subtype demonstrates a translocation in t(2;13) (PAX3-FOXO1). The malignant cells show a spectrum of small round cells and pleomorphic large cells with rhabdoid morphology. RMS cells characteristically express myogenin and MyoD1, markers of skeletal muscle differentiation. Although SCNC is not a classic SRCT, the morphology is similar. SCNC demonstrates tight clusters of malignant cells with nuclear molding and salt-and-pepper chromatin. This tumor classically has neuroendocrine differentiation and is positive for synaptophysin and chromogranin on immunohistochemistry. And last, desmoplastic SRCT typically presents as an intra-abdominal mass in young men and characteristically harbors the translocation t(11;22) (p13;q12) (EWSR1-WT1). Cytomorphologically, the tumor shows small monomorphic cells occasionally arranged as rosette-like structures.

KEY MESSAGE

The diagnosis of SRCT can be made in effusion samples and is best achieved with a combination of morphologic features, clinical history, and ancillary testing.

Giant primitive neuroectodermal pelvic tumour: a case report and literature review

Primitive neuroectodermal tumours (PNETs) are rare malignant small round cell tumours. Notably, despite widespread reports of PNET in multiple parts of the body, it is extremely rare in the pelvis. Here, a rare case of giant PNET of the pelvis, that was treated with surgical intervention comprising hemipelvectomy and amputation, is reported. A 42-year-old female patient presented with an enlarged mass on the left hip and severe pain in the left lower extremity for the previous 6 months. Preoperative imaging examinations indicated an irregular soft tissue-like signal shadow sized 19 × 15 × 12 cm at the left ilium and sacrum. After surgical intervention involving left hemipelvectomy and amputation, the tumour was diagnosed by pathology as PNET. During the courses of postoperative radiotherapy and chemotherapy, local recurrence and distant metastasis occurred, and the patient died 9 months following surgical treatment. To the best of the authors' knowledge, the current case is the largest pelvic PNET resection reported to date. Pelvic PNET is extremely malignant and has a high mortality rate regardless of surgical treatment, however, surgical resection of the lesion may relieve the symptoms, extend life, and improve quality of life to a certain extent.

Pulmonary small cell carcinoma: Review, common and uncommon differentials, genomics and management

Lung cancer is the leading cause of cancer-related death worldwide. It is divided into sub-categories based upon morphology, immunostaining pattern, biology, molecular profile, and/or treatment options. Up until the early 2000s when driver mutations with targeted therapies were identified in a subset of adenocarcinomas, the most critical distinction of lung carcinomas was driven by differences in treatment between small cell carcinoma (SCC) and nonsmall cell lung carcinoma (NSCLC). The distinction between SCC and NSCLC remains critical in the 21st century for management, especially for advanced stage cancer. In the vast majority of cases, morphological features are sufficient to separate SCC from other types of lung cancers. In some instances, however, cytomorphological features and immunohistochemical overlap with other tumors, limited sample availability, and/or crush artifact pose diagnostic challenges. The aim of this review is to highlight salient features of SCC and ancillary studies to distinguish it from common and uncommon potential mimickers, as well as provide updates in genomics and management.

Carcinomas of the Thyroid with Ewing Family Tumor Elements (CEFTEs): A Diagnostic Challenge Before Surgery

Carcinomas of the thyroid with Ewing family tumor elements (CEFTEs) are small cell thyroid tumors characterized by epithelial differentiation and EWSR1-FLI1 rearrangements. In contrast to primary thyroid Ewing sarcomas, these rare tumors have a favorable prognosis. CEFTEs may co-exist with papillary thyroid carcinoma (PTC) foci and are thought to arise from either PTCs or main cells of solid cell nests (SCN). Due to their rare occurrence, characteristic clinical presentations, preoperatory sonographic (US) findings, and fine-needle aspiration (FNA) cytologic features were ill-defined until now. We report a case of a 40-year-old male who was referred to the thyroid clinic for a progressively enlarging, hard, painless, cervical mass. US examination revealed a hypoechoic nodule with lobulated margins and scant intranodular vascular signals of the right thyroid lobe. Evidence of extracapsular spread was not identified. FNA provided a Bethesda V cytology classification on conventional smears. Repeat FNA sampling with the use of a CytoFoam Core allowed a preoperative diagnosis consistent with undifferentiated thyroid carcinoma. Total thyroidectomy without lymph node dissection was performed. Histologic examination with subsequent molecular studies provided the diagnosis of papillary carcinoma of the thyroid with Ewing family tumour elements (CEFTEs). No additional treatment was rendered and the patient showed no evidence of local or distant disease by clinical examination, US, and ¹⁸FDG-TAC/PET after 6 months of follow-up. This is the first reported case of CEFTE with complete clinical, US, cytologic, and immunohistochemical preoperatory assessment.

Extraskeletal Ewing's sarcoma/peripheral primitive neuroectodermal tumor of the small bowel presenting with gastrointestinal perforation

Extraskeletal Ewing’s sarcoma (E-EWS)/peripheral primitive neuroectodermal tumor (pPNET) is a rare soft tissue tumor that arises from a multipotent progenitor cell and is considered to be of neuroectodermal origin. Although soft tissue E-EWS/pPNETs are common, they are exceedingly rare in the small bowel. Only 30 cases of E-EWS/pPNET of the small bowel have been reported. However, only one case of gastrointestinal perforation has been reported till today. Here, we report the second case of E- EWS/pPNET with gastrointestinal perforation.

Adjuvant chemotherapy for a primitive neuroectodermal tumor of the uterine corpus: A case report and literature review

A primitive neuroectodermal tumor (PENT) belongs to the category of a Ewing sarcoma. A PENT of the uterus is rare and has been known to be very aggressive by nature. Owing to the rarity of the tumor, there is no optimal treatment at present. In many cases, after hysterectomy, chemotherapy or radiation therapy has been performed. However, an effective chemotherapy regimen was unclear. In the soft tissue sarcoma area, the chemotherapy approach has recently greatly improved. Vincristine, doxorubicin, cyclophosphamide, ifosfamide and etoposide (VDC-IE) therapy has improved the survival rate of patients with Ewing sarcoma/PENT. Thus, VDC-IE therapy may be used for a uterine PENT. Here, we report a case of a uterine PENT in a premenopausal woman successfully treated with multimodality treatment including VDC-IE therapy and discuss the optimal chemotherapy for a uterine PENT through a literature review.

Cytodiagnosis of Extraskeletal Ewing's Sarcoma and its Confirmation by Fluorescence in situ Hybridization

Extraskeletal Ewing's sarcoma is an aggressive malignant small round cell tumour usually occuring in children and adolescents. It needs to be differentiated from other malignant small round cell tumours and immunohistochemistry plays a pivotal role in establishing the diagnosis. Fluorescence in situ hybridization or real time-polymerase chain reaction helps in confirming the diagnosis by demonstration of EWS-FLI1 translocation, which is found in approximately 85% of the cases. We report a case of extraskeletal Ewing's sarcoma in a10-year-old male, who presented with a right gluteal region mass. Fine needle aspiration and cell block preparation followed by a panel of immunohistochemical markers were performed. Immunohistochemistry for CD99 and FLI1 was positive. EWS-FLI1 translocation was confirmed by fluorescence in situ hybridization.

Pediatric soft tissue tumor pathology: A happy morpho-molecular union

Since its foundation by remarkably talented and insightful individuals, prominently including Pepper Dehner, pediatric soft tissue tumor pathology has developed at an immense rate. The morphologic classification of tumoral entities has extensively been corroborated, but has also evolved with refinement or realignment of these classifications, through accruing molecular data, with many derivative ancillary diagnostic assays now already well-established. Tumors of unclear histogenesis, classically morphologically undifferentiated, are prominent amongst pediatric sarcomas, however, the classes of undifferentiated round- or spindle-cell-tumors-not-otherwise-specified are being dismantled gradually with the identification of their molecular underpinnings. Within recent years, for example, numerous subcategories of 'Ewing-like' round cell sarcoma have emerged. Such advances have provided the basis for novel diagnostic and prognostic sub-classifications. Efforts at defining cell- or lineage-of-origin for several tumor types have produced interesting insights especially for rhabdomyosarcoma. The remarkably early onset of pediatric sarcomas defies the theory necessitating stochastic accumulation of several somatic mutations for cancer development and indeed, these tumors may be remarkably genomically stable, often belying their aggressive nature. Much is coming to light recently regarding the role of epigenetic modifications in the evolution of these sarcomas. Indeed the morphologic features of embryonal tumors generally (not just sarcomas) may be highly reminiscent of arrested differentiation, and given the tight epigenetic regulation of cell fate determination and cell identity maintenance, a theory of epigenetically-driven oncogenesis sits easily with these tumors. The age-delimited distinct biologies of 'pediatric' and adult GIST are intriguing, particularly, the SDH-deficient 'pediatric' form, driven by a metabolic defect, but resulting in epigenetic dysregulation with genome-wide DNA methylation changes. There is little doubt that many of the gaps in our understanding of pediatric sarcoma biology will be filled by a deeper appreciation of the role of dysregulated epigenetics including chromatin biology, perhaps best exemplified in malignant rhabdoid tumor. The field of pediatric soft tissue tumor pathology grows ever more interesting. Importantly though, it must be emphasized, that none of this progress could have occurred, or indeed continue, without the initial step of accurate diagnosis, founded solidly on morphology - thank you Pepper for your unparalleled contributions to this field! The opportunity to be your apprentice for five years has been a bigger and more positive influence than words can express.

Primary Brachial Plexus Tumors: Clinical Experiences of 143 Cases

OBJECTIVE

Primary brachial plexus tumors are extremely rare and the treatment is challengeable. Our aim is to share the experiences in the treatment of primary brachial plexus tumors.

METHODS

A retrospective analysis of 143 patients with primary brachial plexus tumors was made in our department from January 2001 to December 2012. The clinical presentation of the patients, the characteristics and pathological results of the tumors and the prognosis were described.

RESULTS

Seventy-eight males and sixty-five female were enrolled. The mean age was 48.17 years old. A palpable mass was the most common clinical presentation occurred in 129 patients. The trunks of the brachial plexus were the locations where the tumors originated with high possibility, with 68 cases. Benign tumors were composed of 119 schwannomas and 12 neurofibromas, while malignant tumors were composed of 8 malignant peripheral nerve sheath tumors, 2 malignant granular cell tumors, 1 synovial sarcoma and 1 peripheral primitive neuroectodermal tumor. Appropriate surgical method, radiotherapy and chemotherapy were used according to the condition during operation, preoperative examinations and pathological result. The survival rate was 50.00% with a 3-year follow-up. Local recurrence happened in 7 patients. Five patients presented Metastasis.

CONCLUSIONS

Appropriate surgical method is the key for the treatment of different brachial plexus tumors. Surgery has a great effect on the treatment of benign tumors. For malignant tumors, adjuvant radiotherapy or chemotherapy should be used according to the pathological result. The general prognosis for malignant brachial plexus tumors is less than ideal.

Ewing's Sarcoma of Mandible: An Impressive Case of Spontaneous Mandible Regeneration

Ewing's sarcoma (ES) is an uncommon aggressive bone malignancy that mainly affects children and adolescents. Mandible involvement is quite rare and usually represents metastasis from another skeletal site. Combined therapy including wide surgical resection and preoperative and postoperative chemotherapy has been demonstrated as the mainstay of therapeutic approach. As improved therapeutic modalities have significantly increased survival over the last decades, functional and esthetic reconstruction of the postmandibulectomy defect is usually necessary for patient's total rehabilitation. We report a case of ES of the mandible with special consideration to the postresection spontaneous structural and functional regeneration of the mandible.

HOW TO CITE THIS ARTICLE

Chatzistefanou I, Kabesi S, Paraskevopoulos K, Koliouskas D, Antoniades K. Ewing's Sarcoma of Mandible: An Impressive Case of Spontaneous Mandible Regeneration. Int J Clin Pediatr Dent 2016;9(3):273-277.

Adamantinoma-like Ewing sarcoma mimicking basal cell adenocarcinoma of the parotid gland: a case report and review of the literature

Adamantinoma-like Ewing sarcoma (AES) is a rare variant of the Ewing family of tumors that resembles classic adamantinoma of bone. AES shows epithelial differentiation and a more complex immunohistochemical expression profile with keratin and basal marker immunoreactivity and can resemble a variety of carcinomas. We report an unusual case of an AES of the parotid gland that mimicked a basal cell adenocarcinoma. Like basal cell adenocarcinoma, this AES showed a nested basaloid proliferation with peripheral palisading in tumor nests with 'basaloid' epithelial differentiation as highlighted by cytokeratin AE1/3 and p40 positivity. However, unlike most basal cell adenocarcinomas, this tumor demonstrated high grade morphology, showed no true ductal or myoepithelial component, and also showed a tendency towards neuroectodermal phenotype with focal rosette formation, CD99 and weak synaptophysin immunoreactivity. EWSR1 and FLI1 fluorescence in situ hybridization confirmed the presence of a translocation supporting the diagnosis of AES. This is the first case of AES presenting as a primary parotid mass highlighting the potential to be mistaken for primary salivary gland carcinomas, which in addition to basal cell adenocarcinoma include other basaloid tumors such as adenoid cystic carcinoma.

Clinical, pathological, and imaging characteristics of primitive neuroectodermal tumors of the spine

Primitive neuroectodermal tumors (PNETs) located in the spine are extremely rare, and information concerning these tumors in the medical literature is limited to single case reports. This pictorial essay presents the clinical, pathological, and imaging characteristics of PNET of the spine.

From cytomorphology to molecular pathology: maximizing the value of cytology of lymphoproliferative disorders and soft tissue tumors

OBJECTIVES

The field of cytopathology has been rapidly advancing in the era of molecular pathology and personalized medicine. On-site cytologic evaluation for adequacy and triaging specimens for small core biopsy or fine-needle aspiration (FNA) are often required. Cytopathologists face the challenge of how to best triage small specimens for diagnosis, molecular testing, and personalized treatment. Owing to its minimally invasive nature, FNA alone or combined with core biopsy for lymphoproliferative disorders and soft tissue tumors has gained popularity.

METHODS

Literature review and author's institutional experience are used for this review article. This article will focus mainly on lymphoproliferative disorders and soft tissue tumors.

RESULTS

Evaluation combining cytomorphology, immunohistochemistry, and/or molecular pathology is often needed to accurately diagnose and classify lymphomas and soft tissue tumors. Many molecular tests have been performed on cytologic specimens, such as tests for BRAF and RET in thyroid FNA.

CONCLUSIONS

Molecular pathology has been widely integrated into conventional cytopathology for diagnosing lymphoproliferative disorders and soft tissue tumors, and the diagnostic value of FNA on those tumors has increased significantly. Cytology will play a more important role in the era of personalized medicine.

A Radiological Review of Ewing's Sarcoma of Mandible: A Case Report with One Year Follow-up

Ewing's sarcoma (ES) is an uncommon round cell tumor with an aggressive course affecting mainly children and young adults. Only 1% of cases is reported with jaw involvement and have mandibular predilection. Radiographic finding in ES reflect many destructive nature of the lesion, like osteolysis, cortical erosion, periostitis and soft tissue mass. A case of ES of the mandible is reported with special consideration to the radiological appearance.

How to cite this article: Krishna KBB, Thomas V, Kattoor J, Kusumakumari P. A Radiological Review of Ewing's Sarcoma of Mandible: A Case Report with One Year Follow-up. Int J Clin Pediatr Dent 2013;6(2):109-114.

Five Top Stories in Cytopathology

Context.—Cytology relies heavily on morphology to make diagnoses, and morphologic criteria have not changed much in recent years. The field is being shaped predominantly by new techniques for imaging and for acquiring and processing samples, advances in molecular diagnosis and therapeutics, and regulatory issues.

Objective.—To review the importance of classical morphology in the future of cytopathology, to identify areas in which cytology is expanding or contracting in its scope, and to identify factors that are shaping the field.

Data Sources.—Literature review.

Conclusions.—Five stories paint a picture in which classical cytomorphology will continue to have essential importance, both for diagnosis and for improving our understanding of cancer biology. New endoscopy and imaging techniques are replacing surgical biopsies with cytology samples. New molecularly targeted therapies offer a chance for cytology to play a major role, but they pose new challenges. New molecular tests have the potential to synergize with, but not replace, morphologic interpretation of thyroid fine-needle aspirations. Ultrasound-guided fine-needle aspiration performed by cytopathologists is opening a new field of “interventional cytopathology” with unique value. For the productive evolution of the field, it will be important for cytopathologists to play an active role in clinical trials that document the ability of cytology to achieve cost-effective health care outcomes.

An Unusual Location of Extraosseous Ewing's Sarcoma

Ewing's sarcoma (ES) is the second most common malignant bone tumor in children and young adults. ES also occurs as a primary soft tissue neoplasm without involvement of bone. We report the second case of extraosseous (EO) ES emerging from the omentum and a review of the relevant literature. EO ES should be included in the differential diagnosis of soft tissue neoplasms in the abdomen.

Bone Cytology: A Realistic Approach for Clinical Use

This article presents the use of bone cytology for diagnosis of bone tumors. It discusses critical factors and considerations of fine-needle aspiration and bone cytology and presents diagnostic options and differential diagnosis for benign and malignant bone lesions. Osteomyelitis, chrondroblastoma, Langerhans cell histiocytosis, chondromyxoid fibromas, enchondromas, giant cell tumor of bone, osteosarcoma, chondrosarcoma and variants, Ewing sarcoma, chordoma, plasmacytoma, multiple myeloma, lymphoma, and metastatic bone disease are presented.

Advances in fine needle aspiration cytology for the diagnosis of pulmonary carcinoma

New developments in the field of thoracic oncology have challenged the way pathologists approach the diagnosis of pulmonary carcinoma. Nonsmall cell carcinoma is no longer an adequate diagnostic category. Pathologists are required to further classify tumors into adenocarcinoma and squamous cell carcinoma since specific therapies are now recommended depending on the histological tumor type. This change occurred following the discovery of specific molecular alterations that predict response to certain drugs and now molecular testing of tumor cells is often requested to direct therapy. The vast majority of lung cancer is diagnosed in advanced clinical stages, where cytologic or small biopsy material is the only form of tissue diagnosis, thus placing cytology, especially fine needle aspiration biopsy in the front line for management of patients with lung cancer. In this paper we will review the current concepts in the suitability and accuracy of fine needle aspiration biopsy, including diagnosis, classification, prognostic markers, and use of ancillary techniques.

EUS-FNA for the Diagnosis of Retroperitoneal Primitive Neuroectodermal Tumor

Primitive neuroectodermal tumor (PNET) is a rare "small round blue cell tumor" that is diagnosed by open biopsy or percutaneous biopsy of the lesion under radiologic guidance. In this case report, we present a novel approach to the diagnosis of a retroperitoneal PNET by endoscopic ultrasound- (EUS-) guided fine needle aspiration (FNA). A 35-year-old man presented with the history of left-sided flank pain and swelling of 3-weeks duration. Computerized tomography (CT) scan of his abdomen revealed a 12.8 × 13 × 12.5 cm cystic and solid mass arising from the retroperitoneum and displacing the third and fourth portions of the duodenum. He underwent EUS which revealed a well-circumscribed heterogeneous mass abutting the inferior portion of the stomach. EUS-FNA of the mass revealed malignant cells consistent with primitive neuroectodermal tumor (PNET)/Ewing's sarcoma. EUS-guided FNA is an appropriate technique for diagnosing retroperitoneal PNET/Ewing's sarcoma.

Detection of SYT and EWS gene rearrangements by dual-color break-apart CISH in liquid-based cytology samples of synovial sarcoma and Ewing sarcoma/primitive neuroectodermal tumor

To improve cytologic diagnostic accuracy for translocation-associated sarcomas, we explored dual-color break-apart (dc) chromogenic in situ hybridization (CISH) on liquid-based cytology (LBC) samples of 2 prototypic sarcomas: synovial sarcoma (SS) and Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET). LBC samples of 10 cases of SS and 9 cases of ES/PNET were subjected to dc-CISH using probes for the specifically rearranged genes in each tumor entity: SYT in SS and EWS in ES/PNET. Rearranged SYT was successfully detected in all SSs but not in any ES/PNETs. In contrast, EWS rearrangement was identified in all ES/PNETs but not in any SSs. These results were validated by dc-fluorescence in situ hybridization and reverse transcription-polymerase chain reaction. dc-CISH on LBC samples is a reliable modality to detect gene rearrangements in sarcomas. This system has a clear advantage over other methods, enabling simultaneous visualization of the genetic abnormality and well-preserved, nonoverlapping cytomorphologic features with clear background under bright-field microscope.