Malignant myxoid endobronchial tumour: a report of two cases with a unique histological pattern

Primary Pulmonary Myxoid Sarcoma and Thoracic Angiomatoid Fibrous Histiocytoma: Two Sides of the Same Coin?

Primary pulmonary myxoid sarcoma (PPMS) and thoracic angiomatoid fibrous histiocytoma (AFH) are rare neoplasms with EWSR1 fusions and overlapping morphology. Both tumor types often show epithelial membrane antigen expression, but AFH characteristically co-expresses desmin. We encountered a case of PPMS with the unexpected finding of patchy, strong anaplastic lymphoma kinase (ALK) (previously reported in AFH) and synaptophysin expression. We evaluated a cohort of PPMS and thoracic AFH with systematic morphologic comparison and surveyed for aberrant expression of ALK and synaptophysin. Medical records and slides were reviewed for 16 molecularly confirmed cases of PPMS (n=5) and thoracic AFH (n=11). Each case was scored for morphologic characteristics typical of PPMS and/or AFH. ALK, synaptophysin, chromogranin, desmin, and epithelial membrane antigen immunostains were performed on cases with available tissue. AFH and PPMS cases showed similar age at presentation and long-term tumor behavior. Almost all cases of PPMS and AFH had a fibrous pseudocapsule and lymphoid rim. All PPMS had myxoid stroma and reticular growth pattern, but these features were also present in a subset of AFH. Synaptophysin expression was present in 6 of 11 AFH and 1 of 5 PPMS; all tested cases were negative for chromogranin (n=15). One case of AFH and 1 case of PPMS showed focally strong coexpression of synaptophysin and ALK. AFH and PPMS show considerable clinicopathologic overlap. When supportive, the immunohistochemical findings described may aid in diagnosis before molecular confirmation. PPMS and AFH may be morphologic variants of the same clinicopathologic entity, which can show more immunophenotypic variability than previously reported.

Back to the future! Selected bone and soft tissue neoplasms with shared genetic alterations but differing morphological and immunohistochemical phenotypes

Bone and soft tissue tumors (BST) are a highly heterogeneous group largely classified by their line of differentiation, based on their resemblance to their normal counterpart in adult tissue. Yet, rendering a specific diagnosis can be challenging, primarily due to their rarity and overlapping histopathologic features or clinical presentations. Over the past few decades, seemingly histogenetic-specific gene fusions/translocations and amplifications have been discovered, aiding in a more nuanced classification, leading to well-established objective diagnostic criteria and the development of specific surrogate ancillary tests targeting these genetic aberrations (e.g., immunohistochemistry). Ironically, the same research also has revealed that some specific tumor subtypes may be the result of differing and often multiple gene fusions/translocations, but, more interestingly, identical gene fusions may be present in more than one phenotypically and biologically distinct neoplasm, sometimes with entirely different clinical behavior. Prime examples include, EWSR1::ATF1 and, less commonly, EWSR1::CREB1 gene fusions present in both clear cell sarcoma, a malignant high-grade tumor with melanocytic differentiation, and angiomatoid fibrous histiocytoma, a mesenchymal neoplasm of intermediate malignancy with a generally indolent course. Similarly, MDM2 amplification, once deemed to be pathognomonic for atypical lipomatous tumor/well differentiated and dedifferentiated liposarcoma, has been documented in a range of additional distinct tumors, including low grade osteosarcomas (e.g. low grade central and surface parosteal) and high-grade intimal sarcomas, amongst others. Such findings reinforce the importance of careful attention to morphological and clinicoradiological features and correlation with molecular testing before rendering a specific diagnosis. Future classification systems in BST neoplasms cannot be solely based on molecular events and ideally will balance morphologic features with molecular analysis. Herein, we provide a narrative literature review of the more common BST neoplasms with shared genetic events but differing demographics, morphology, immunophenotype, and clinical behavior, re-emphasizing the importance of the hematoxylin and eosin slide and the "eye" of the practicing pathologist.

Primary pulmonary myxoid sarcoma with EWSR1::CREB1 fusion: a literature review

PURPOSE

This review primarily aims to review the epidemiology, clinical characteristics, imaging, pathology, immunohistochemistry, diagnosis, differential diagnosis, treatment, and prognosis of Primary pulmonary myxoid sarcoma (PPMS) with EWS RNA binding protein 1::cAMP response element binding protein 1 (EWSR1::CREB1) fusion. It provides reference for the diagnosis and treatment of this disease.

METHODS

Retrospectively collected the literature about PPMS with EWSR1::CREB1 fusion, its clinical, radiology, histology, molecular characteristics and current treatment strategies were collated and analyzed. This review provides a detailed differential diagnosis of the disease.

RESULTS

PPMS is an exceptionally rare, low-grade malignant tumor of the lung. This tumor commonly infiltrates lung tissue and develops within bronchial passages. It is identified by a genetic rearrangement involving the EWSR1 gene and a distinct chromosomal translocation t(2; 22)(q33; q12). Variants include EWSR1::CREB1 fusion and EWS RNA binding protein 1::activating transcription factors (EWSR1::ATF1) fusion. PPMS with EWSR1::CREB1 fusion is more prevalent among middle-aged individuals and affects both sexes almost equally. Clinical symptoms are relatively non-specific, primarily including cough, hemoptysis, and weight loss. Most patients undergo surgery and experience a favorable prognosis. Further research is required to validate the effectiveness of alternative treatments for PPMS with EWSR1::CREB1 fusion.

CONCLUSION

EWSR1 rearrangement and EWSR1::CREB1 fusion are crucial genetic features of PPMS and serve as important diagnostic markers. Immunohistochemically, PPMS tests positive for EMA. In terms of treatment, surgery has been the primary approach in recent years. Therefore, the efficacy of other treatments still requires further investigation.

[Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion]

Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion is an extremely rare tumor. Its clinical manifestation is unspecific and only molecular genetic method can proof this diagnosis. This paper describes an unusual clinical presentation of primary pulmonary myxoid sarcoma in a 68-year-old patient with involvement of both lungs.

Primary Pulmonary Myxoid Sarcoma with EWSR1::ATF1 Fusion: A Case Report

Primary pulmonary myxoid sarcoma is a rare lung sarcoma, mostly involving the central lung and harboring the EWSR1::CREB1 fusion. We report an exceptional case of primary pulmonary myxoid sarcoma arising in the peripheral lung and harboring an EWSR1::ATF1 gene fusion. A 67-year-old man presented with a solid nodule in the right lower lobe, and wedge resection was performed. Microscopically, the tumor consisted of reticular proliferation of uniform mildly atypical spindle cells within abundant myxoid stroma. Immunohistochemically, smooth muscle actin was positive but desmin was negative. Fluorescence in situ hybridization confirmed EWSR1 and ATF1 gene rearrangements. No recurrence was seen for 12 months. Pathological findings and gene rearrangements are important for the diagnosis of primary pulmonary myxoid sarcoma. Complete resection and careful observation are required.

CT findings of a large primary pulmonary myxoid sarcoma: A case report

Primary pulmonary myxoid sarcoma (PPMS) is an extremely rare malignant mesenchymal tumor of the lung, with only less than 40 cases reported. We described a case of a 64-years-old man with a mass on the medial and lower lobe of the right lung confirmed as a primary pulmonary myxoid sarcoma on biopsy. Diagnosis of this tumor remains challenging because of its nonspecific clinical and imaging characteristics. This study emphasizes CT finding to improve the understanding of PPMS.

Primary Pulmonary Myxoid Sarcoma and Myxoid Angiomatoid Fibrous Histiocytoma: A Unifying Continuum With Shared and Distinct Features

Primary pulmonary myxoid sarcoma (PPMS) is a recently reported, exceedingly rare low-grade lung neoplasm characterized by reticular/lace-like growth of spindle to epithelioid cells embedded in an abundant myxoid matrix. Morphologically, it overlaps with a myxoid variant of angiomatoid fibrous histiocytoma (AFH) of the soft tissue. Genetically, they were both reported to harbor EWSR1-CREB1 fusion, while EWSR1-ATF1 has only been reported in AFH thus far. We report a case of primary pulmonary low-grade myxoid spindle cell tumor with morphologic and immunohistochemical features of PPMS but with an EWSR1-ATF1 fusion gene. In addition, we also encountered a case of endobronchial AFH with EWSR1-CREB1 translocation but also focal morphologic features of PPMS. These findings provide new evidence supporting the concept that PPMS and a myxoid variant of AFH represent a continuum with overlapping histologic, immunohistochemical, and genetic features.

Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion: a case report and review of the literature

BACKGROUND

Primary pulmonary myxoid sarcoma (PPMS) is an extremely rare lung sarcoma that is characterized in most cases by recurrent balanced chromosomal translocation t(2;22)(q33;q12) leading to the oncogenic fusion gene EWSR1-CREB1.

CASE PRESENTATION

We report a case of PPMS with molecular confirmation using fluorescence in situ hybridization (FISH) and DNA sequencing in a 45-year-old female patient. Computer tomography (CT) scanning revealed a peripheral circumscribed solid mass of 2.1 × 2 cm in the right lung superior lobe. Histologically, the tumor cells ranged from stellate, polygonal to chondrocyte-like or physaliferous-like, forming reticular network of delicate lace-like cellular strands and cords in abundant myxoid stroma. The tumor cell immunophenotype was positive for vimentin, EMA and negative for CK-pan, TTF-1, CAM5.2, S-100, calponin, SMA, desmin, ALK, CD31 and CD34. Molecular analysis demonstrated EWSR1-CREB1 gene fusion in this tumor. During 38 months of follow-up, the patient was alive with no clinical or radiological evidence of recurrence or metastasis.

CONCLUSION

PPMS is a rare low-grade sarcoma with distinct histological and genetic features. We add another case to the literature of this rare tumor and report for the first time occurrence of chondrocyte-like and physaliferous-like tumor cells in this tumor, thus enriching its morphologic and cytologic spectrum.

Primary pulmonary myxoid sarcoma with an unusual gene fusion between exon 7 of EWSR1 and exon 5 of CREB1

Primary pulmonary mesenchymal tumors are rare, yet they compromise a variety of entities. A novel low-grade malignant neoplasm coined primary pulmonary myxoid sarcoma (PPMS) has been introduced in the WHO classification of lung tumors. Molecular analysis in PPMS revealed recurrent gene fusions between EWSR1 and CREB1, a member of the cAMP response element binding protein (CREB) family. However, only 23 PPMS have been reported in the literature reflecting their exceedingly low incidence. Here, we describe the case of a 41-year-old female patient with a lung tumor obstructing the right main bronchus. Histologically, the tumor was composed of spindle-shaped and epithelioid cells exhibiting a reticular growth pattern within a prominent myxoid matrix. Solid areas were also observed. Molecular analysis by next-generation sequencing identified a fusion transcript with an unusual gene fusion involving exon 7 of EWSR1 and exon 5 of CREB1. Together, the diagnosis PPMS was established.

Endobronchial Myxoma: An Uncommon Entity

A 31-year-old woman presented with progressive breathlessness since 1 year. Flexible bronchoscopy revealed a vascular tumor completely occluding the right main bronchus. A diagnosis of primary endobronchial myxoma was made. Tumor debulking was performed using rigid bronchoscopy. This enabled right lower lobectomy. A literature search yielded 12 cases of primary pulmonary myxoma, and only 2 previous reports of endobronchial myxoma. Most tumors were incidentally detected and were cured surgically. Endobronchial myxomas are rare and are usually asymptomatic. Treatment involves surgical excision. Rigid bronchoscopy serves as a bridge to surgery and can reduce the extent of surgery.

Primary pulmonary myxoid sarcoma located in interlobar fissure without parenchymal invasion

Primary pulmonary myxoid sarcoma (PPMS), classified as low to intermediate grade malignant myxoid endobronchial tumor, is rarely reported. Most reported cases occurred in lung parenchyme with an endobronchial component. Herein, we report a case of PPMS in a 29‐year‐old woman that developed in a major fissure of the left lung without parenchymal invasion. Histopathologically, the diagnosis was compatible to PPMS with EWSR1‐CREB1 translocation.

Primary Pulmonary Myxoid Sarcoma: A Newly Described Entity-Report of a Case and Review of the Literature

Primary pulmonary myxoid sarcoma (PPMS) is a recently described, exceedingly rare low-grade lung sarcoma that tends to present in young females as an endobronchial mass and shows evidence of an EWSR1- CREB1 fusion. Herein, we present a case of PPMS with fluorescence in situ hybridization (FISH) analysis for EWSR1 and CREB1 rearrangements. An 80-year-old woman presented with an endobronchial, multinodular tumor exhibiting spindle, ovoid and epithelioid cells arranged in reticular/lattice-like and alveolar-like patterns in a myxoid background. The tumor showed focal epithelial membrane antigen immunoreactivity as well as an Alcian blue-positive stroma that was sensitive to digestion with hyaluronidase. EWSR1 and CREB1 rearrangements were detected by break-apart FISH probes. The patient showed persistence of disease 36 months after diagnosis and was discharged to hospice care. We contribute with a report of an additional case of this very unusual entity and perform a brief review of the literature published so far on the subject.

The 2015 World Health Organization Classification of Lung Tumors: Impact of Genetic, Clinical and Radiologic Advances Since the 2004 Classification

The 2015 World Health Organization (WHO) Classification of Tumors of the Lung, Pleura, Thymus and Heart has just been published with numerous important changes from the 2004 WHO classification. The most significant changes in this edition involve (1) use of immunohistochemistry throughout the classification, (2) a new emphasis on genetic studies, in particular, integration of molecular testing to help personalize treatment strategies for advanced lung cancer patients, (3) a new classification for small biopsies and cytology similar to that proposed in the 2011 Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification, (4) a completely different approach to lung adenocarcinoma as proposed by the 2011 Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification, (5) restricting the diagnosis of large cell carcinoma only to resected tumors that lack any clear morphologic or immunohistochemical differentiation with reclassification of the remaining former large cell carcinoma subtypes into different categories, (6) reclassifying squamous cell carcinomas into keratinizing, nonkeratinizing, and basaloid subtypes with the nonkeratinizing tumors requiring immunohistochemistry proof of squamous differentiation, (7) grouping of neuroendocrine tumors together in one category, (8) adding NUT carcinoma, (9) changing the term sclerosing hemangioma to sclerosing pneumocytoma, (10) changing the name hamartoma to "pulmonary hamartoma," (11) creating a group of PEComatous tumors that include (a) lymphangioleiomyomatosis, (b) PEComa, benign (with clear cell tumor as a variant) and

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.

Primary pulmonary myxoid sarcomas with EWSR1-CREB1 translocation might originate from primitive peribronchial mesenchymal cells undergoing (myo)fibroblastic differentiation

Primary pulmonary myxoid sarcoma (PPMS) is a very rare lung tumor that has recently been shown to harbor an EWSR1-CREB1 translocation. However, the histogenesis and biological behavior of PPMS remains unclear. To provide insight into the histogenesis of PPMS, we studied surgical resection specimens of four patients, two females and two males with an age range of 26 to 65 years, all non-smokers with mild anemia. The tumors, three of which are endobronchial, measured between 4 and 13 cm. One patient developed metastasis to the contra-lateral lung 7 months after resection. Other patients remained alive without tumor for 1.5, 10, and 13 years. Fluorescence in situ hybridization (FISH) analysis with a gene break apart probe showed an EWSR1 translocation in all cases. The EWSR1-CREB1 fusion transcript was detected in all cases by reverse-transcription PCR. Immunohistochemical staining showed diffuse positive staining of the tumor cells only for vimentin. Tumor cells expressed no other myoid, epithelial, endothelial, melanocytic, myoepithelial, or neuroendocrine markers, except for smooth muscle actin and epithelial membrane antigen, which were only focally positive in individual cases. Ultrastructural analyses revealed the presence in the tumor cells of intermediate filaments with focal densities along the sub-cytoplasmic membrane as well as dense plaques. These results suggest that PPMS exhibits myofibroblastic differentiation. We conclude that PPMS is an intermediate grade malignant lung tumor harboring EWSR1 translocations, which may originate from mesenchymal cells that undergo fibroblastic or myofibroblastic differentiation.

Tumors with EWSR1-CREB1 and EWSR1-ATF1 fusions: the current status

EWSR1-CREB1 and EWSR1-ATF1 are gene fusions of which one or both have now been consistently described in 5 histopathologically and behaviorally diverse neoplasms: angiomatoid fibrous histiocytoma, conventional clear cell sarcoma (of tendons and aponeuroses), clear cell sarcoma-like tumor of the gastrointestinal tract, hyalinizing clear cell carcinoma of the salivary gland, and primary pulmonary myxoid sarcoma. Some of the tumors in this group have been described only recently, and others have been the subject of recent genetic insights contributing to their characterization. These neoplasms are all rare; yet, the increasing frequency with which EWSR1-CREB1 and EWSR1-ATF1 fusions are being described in separate entities is noteworthy. The additional molecular mechanisms by which tumors with such variable morphologic, immunohistochemical, and clinical phenotypes are generated are yet to be understood. We review the clinicopathologic and molecular features of this group of neoplasms unified by the presence of EWSR1-CREB1 and EWSR1-ATF1 genetic fusions.

Endobronchial myxoma--case report

INTRODUCTION

Pulmonary myxoma is an extremely rare benign neoplasm. It is mostly parenchymal but may occasionally occur within the tracheobronchial tree. There are very few reports of endobronchial myxoma.

CASE REPORT

We describe a case of endobronchial myxoma in a 40-year-old female patient with a history of asthma and repeated right-sided pneumonia. Thoracic computed tomography (CT) showed medium lobe atelectasis. Fiber optic bronchoscopy revealed a polypoid, well-circumscribed tumor, causing total obstruction of the medium lobe bronchus. Biopsy of the mass was non-diagnostic. Further study included a positron emission tomography (PET) which demonstrated low metabolic activity of the tumor and no evidence of neoplasia in other location. The patient was submitted to a medium lobectomy and microscopic examination of the tumor revealed myxoid stroma with lobulated pattern, elongated and stellate cells, compatible with myxoma.

CONCLUSION

Pulmonary myxoma is extraordinary rare and endobronchial location is very few reported in medical literature.

Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion: a new tumor entity

We present clinicopathologic data on 10 pulmonary myxoid sarcomas, which are defined by distinctive histomorphologic features and characterized by a recurrent fusion gene, that appear to represent a distinct tumor entity at this site. The patients [7 female, 3 male; aged 27 to 67 y (mean, 45 y)] presented with local or systemic symptoms (n=5), symptoms from cerebral metastasis (1), or incidentally (2). Follow-up of 6 patients showed that 1 with brain metastasis died shortly after primary tumor resection, 1 developed a renal metastasis but is alive and well, and 4 are disease free after 1 to 15 years. All tumors involved pulmonary parenchyma, with a predominant endobronchial component in 8 and ranged from 1.5 to 4 cm. Microscopically, they were lobulated and composed of cords of polygonal, spindle, or stellate cells within myxoid stroma, morphologically reminiscent of extraskeletal myxoid chondrosarcoma. Four cases showed no or minimal atypia, 6 showed focal pleomorphism, and 5 had necrosis. Mitotic indices varied, with most tumors not exceeding 5/10 high-power fields. Tumors were immunoreactive for only vimentin and weakly focal for epithelial membrane antigen. Of 9 tumors, 7 were shown to harbor a specific EWSR1-CREB1 fusion by reverse transcription-polymerase chain reaction and direct sequencing, with 7 of 10 showing EWSR1 rearrangement by fluorescence in situ hybridization. This gene fusion has been described previously in 2 histologically and behaviorally different sarcomas: clear cell sarcoma-like tumors of the gastrointestinal tract and angiomatoid fibrous histiocytomas; however, this is a novel finding in tumors with the morphology we describe and that occur in the pulmonary region.

Pulmonary salivary gland-type tumors with features of malignant mixed tumor (carcinoma ex pleomorphic adenoma): a clinicopathologic study of five cases

We report 5 cases of pulmonary salivary gland-type tumors with features of carcinoma ex pleomorphic adenoma. Patient ages ranged from 44 to 71 years (mean, 53.8 years); 4 patients were men and 1 was a woman. In all 5 cases, the lesions were associated with the bronchial system. None of the patients had a history of a head and neck salivary gland neoplasm. Histologically, the lesions were invasive tumors containing malignant myoepithelial elements and duct-like structures embedded in a benign chondromyxoid stroma. Areas reminiscent of residual pleomorphic adenoma were noted in 2 cases. Follow-up for 3 patients revealed that 2 died 22 and 54 months after diagnosis and 1 was alive 20 months after diagnosis. The cases are characterized by unique morphologic features that, coupled with their immunoprofile, suggest the possibility that these tumors represent carcinoma ex pleomorphic adenoma, an entity that has not been well documented in the bronchopulmonary system.

Pulmonary Microcystic Fibromyxoma: Report of 3 Cases

Three cases of pulmonary myxoid tumors showing a variable degree of microcystic change are described. They are presented as incidental solitary peripheral lung nodules on routine radiologic studies. The patients included 2 women, 45 and 65 years old, and 1 man, 33 years old. Clinical work-up showed no evidence of neoplasia in other sites. Following surgical resection, no evidence of disease was observed after a mean follow-up of 48 months. The tumors ranged in size from 1 to 2.3 cm (mean 1.4 cm). Microscopically, the lesions were well circumscribed with conspicuous cystic change and myxoid stroma. Innocuous, widely-spaced, spindled to stellate tumor cells showed minimal nuclear pleomorphism and absence of mitotic activity. The myxoid stroma contained acid mucopolysaccharides, sensitive to hyaluronidase digestion. No epithelial, chondroid, neural, myofibroblastic, lipomatous or vascular differentiation was evident on immunohistochemical studies. Although these cases display cytologic features, myxoid stroma and benign clinical course characteristic of pulmonary myxomas; the presence of microcystic architecture is unique to the current series, and thus a descriptive designation "microcystic fibromyxoma" is suggested.

Low-grade pulmonary myxoid sarcoma of uncertain histogenesis

The present report describes an unusual case of low-grade pulmonary sarcoma with extensive myxoid change in a 60-year-old man. During 30 months, the tumor enlarged gradually and thereafter rapidly to 9 cm. Preoperative biopsy and cytology gave negative results. The resected mass, located at the periphery of the right upper lobe, was well circumscribed and showed gelatinous without necrosis or hemorrhage. Histologically, the tumor was composed of slightly atypical, spindle-shaped or stellate cells, which were loosely distributed within a prominent myxoid stroma. Epithelial differentiation was not seen. Lacunar structures were occasionally evident, but no cartilaginous matrix was seen. Mitotic figures were infrequent. Immunohistochemistry failed to clarify the nature of the neoplastic cells except vimentin positivity. Histochemically, the myxoid ground substance was composed of hyaluronic acid and acid mucopolysaccharide. Electron microscopy revealed no specific differentiation other than aggregates of filaments, which were seen in a number of neoplastic cells. Flow cytometric analysis of the neoplastic cells revealed a diploid pattern. These findings indicated that the neoplasm was a low-grade myxoid sarcoma; however, a definite diagnosis could not be made. The tumor might have been a variant of extraskeletal myxoid chondrosarcoma, especially considering the histochemical results.