Classification of pleomorphic sarcomas: where are we now?

Establishment and characterization of NCC-PS2-C1: a novel cell line of high-grade pleomorphic spindle cell sarcoma, most consistent with myxofibrosarcoma

Pleomorphic sarcoma (PS) is a heterogeneous group of malignant mesenchymal tumors that lack specific histological differentiation. PS is characterized by genetic instability and diversity and unique histological features such as pronounced morphologic pleomorphism. PS is one of the most common soft tissue sarcomas. Complete surgical resection remains the only curative treatment and is often combined with neoadjuvant radiotherapy. Effective systemic chemotherapy is yet to be established, and PS frequently recurs locally and metastasizes to the lungs. Patient-derived cancer cell lines are invaluable tools for basic and preclinical research for developing novel chemotherapies. Herein, we report a high-grade pleomorphic spindle cell sarcoma, most consistent with myxofibrosarcoma cell line, NCC-PS2-C1, which was derived from a primary tumor specimen. NCC-PS2-C1 cells exhibited a range of copy number alterations. This cell line demonstrated consistent proliferation, spheroid formation, and invasive capabilities in vitro. Drug screening using NCC-PS2-C1 cells revealed that cobimetinib, crenolanib, and ixazomib were effective against PS. In conclusion, we established NCC-PS2-C1 cells from primary tumors of PS. This cell line is a valuable resource for developing novel chemotherapies.

A Rare Intruder of the Liver: A Case of Undifferentiated Pleomorphic Sarcoma

Undifferentiated pleomorphic sarcoma (UDS) is a rare and aggressive form of cancer that poses significant diagnostic and therapeutic challenges. The most common sites of this malignancy include the extremities. It is less common in visceral organs and the liver has rarely been reported as a primary site of disease. This subset of cancer is characterized by anaplastic and highly heterogeneous cells that lack specific markers of differentiation, making it difficult to identify and treat effectively. Due to vague symptoms that mirror other pathologies of the affected organ(s), UDS can present like various sarcomas or metastatic processes. A thorough microscopic analysis with the use of ancillary testing including immunohistochemistry can aid in the identification of UDS, as clinical symptoms can be non-specific. It is important to characterize primary malignant lesions since treatment options can range from medical therapy to surgical intervention. We present a unique case of UDS of the liver in a patient with obstructive jaundice.

Stem cell pathology: histogenesis of malignant fibrous histiocytoma and characterization of myofibroblasts appearing in fibrotic lesions

The concept of "stem cell pathology" is to establish the role of the stem cells by exploring their contribution to lesion development. The somatic stem cells are present in the body. Malignant fibrous histiocytoma (MFH; recently named "undifferentiated pleomorphic sarcoma") includes pluripotential undifferentiated mesenchymal stem cells as a cell element. An antibody (A3) generated by using rat MFH cells as the antigen labels somatic stem cells such as bone marrow stem cells and immature endothelial cells and pericytes, as well as immature epithelial cells in epithelialization. By using A3 and other antibodies recognizing somatic stem cells, it is considered that myofibroblasts appearing in rat fibrotic lesions are developed partly from immature hepatic stellate cells in hepatic fibrosis, immature pancreatic stellate cells in pancreatic fibrosis, pericytes/endothelial cells in neovascularization in injured tissues, as well as via the epithelial-mesenchymal transition. These progenitors may be in the stem cell lineage. In this review, the author introduces the histogenesis of MFH and the characteristics of myofibroblasts appearing in fibrosis, based mainly on the author's studies.

Establishment and characterization of NCC-PS1-C1: a novel cell line of pleomorphic sarcoma from a patient after neoadjuvant radiotherapy

Pleomorphic sarcoma (PS) is a heterogeneous group of malignant mesenchymal tumors without a specific histological lineage of differentiation. PS is genetically characterized by genetic instability and diversity and histologically characterized by morphological pleomorphism. PS is one of the most common soft tissue sarcomas. The only curative treatment for PS is complete surgical resection, in which neoadjuvant radiotherapy is frequently combined. PS demonstrates both local recurrence and metastasis after surgical treatment, and effective systemic chemotherapy has not yet been established. Patient-derived cancer cell lines are critical tools for basic and preclinical studies in the development of chemotherapy. However, only six PS cell lines are available from the public cell bank, and none of them are derived from PS after neoadjuvant radiotherapy, despite the fact that radiotherapy causes changes in the posttreatment cancer genome. Here, we reported a novel cell line of PS from a primary tumor specimen resected after neoadjuvant radiotherapy and named it NCC-PS1-C1. NCC-PS1-C1 cells showed a variety of copy number alterations and pathological mutations in TP53. NCC-PS1-C1 cells demonstrated constant proliferation, spheroid formation, and invasion capability in vitro. The screening of antitumor agents in NCC-PS1-C1 cells showed that bortezomib and romidepsin were effective against PS. In conclusion, we report a novel PS cell line from a primary tumor resected after neoadjuvant radiotherapy. We believe that NCC-PS1-C1 will be a useful tool for the development of novel chemotherapies for PS, especially for recurrent cases after neoadjuvant radiotherapy.

G-CSF Production by Undifferentiated Pleomorphic Sarcoma with Leukemoid Reaction Occurred in the Lower Leg: A Case Report

CASE

A 46-year-old woman presented with a mass in the lower leg and severe leukocytosis. Diffuse uptake in the bones was detected with F-fluorodeoxyglucose positron emission tomography with computed tomography (F-FDG PET/CT) imaging. The serum granulocyte-colony stimulating factor (G-CSF) was elevated, and immunostaining for G-CSF was positive. When diagnosed as G-CSF-producing undifferentiated pleomorphic sarcoma (UPS), a wide resection was performed. The leukocytosis and serum G-CSF were remarkably improved after tumor resection. No local recurrence or metastasis was detected.

CONCLUSION

We report the first case of inflammatory UPS in the extremity which demonstrated the neoplastic production of G-CSF. In our case, F-FDG PET/CT, the serum G-CSF, and immunostaining for G-CSF were useful for diagnosis.

The 2020 WHO Classification of Soft Tissue Tumours: news and perspectives

Mesenchymal tumours represent one of the most challenging field of diagnostic pathology and refinement of classification schemes plays a key role in improving the quality of pathologic diagnosis and, as a consequence, of therapeutic options. The recent publication of the new WHO classification of Soft Tissue Tumours and Bone represents a major step toward improved standardization of diagnosis. Importantly, the 2020 WHO classification has been opened to expert clinicians that have further contributed to underline the key value of pathologic diagnosis as a rationale for proper treatment. Several relevant advances have been introduced. In the attempt to improve the prediction of clinical behaviour of solitary fibrous tumour, a risk assessment scheme has been implemented. NTRK-rearranged soft tissue tumours are now listed as an "emerging entity" also in consideration of the recent therapeutic developments in terms of NTRK inhibition. This decision has been source of a passionate debate regarding the definition of "tumour entity" as well as the consequences of a "pathology agnostic" approach to precision oncology. In consideration of their distinct clinicopathologic features, undifferentiated round cell sarcomas are now kept separate from Ewing sarcoma and subclassified, according to the underlying gene rearrangements, into three main subgroups (CIC, BCLR and not ETS fused sarcomas) Importantly, In order to avoid potential confusion, tumour entities such as gastrointestinal stroma tumours are addressed homogenously across the different WHO fascicles. Pathologic diagnosis represents the integration of morphologic, immunohistochemical and molecular characteristics and is a key element of clinical decision making. The WHO classification is as a key instrument to promote multidisciplinarity, stimulating pathologists, geneticists and clinicians to join efforts aimed to translate novel pathologic findings into more effective treatments.

Oral Health and Molecular Aspects of Malignant Fibrous Histiocytoma Patients: A Systematic Review of the Literature

Malignant fibrous histiocytoma is one of the most common soft tissue sarcomas in adults. It occurs only occasionally in oral soft tissues, and knowledge about its characteristics is based on a limited number of cases reported in the literature. Malignant fibrous histiocytoma belongs to the group of soft tissue sarcomas and makes up less than 10% of soft tissue sarcomas. For therapeutic purposes, complete exeresis of the lesion (macroscopic and microscopic) is performed because they have frequent recurrences. As for complementary therapy in addition to surgery, neither radiotherapy nor chemotherapy have been shown to reduce the risk of death related to the disease. Often patients complain of a swelling that grows in a short period of time. It is quite common for patients to report trauma in the area, which is not the cause, but rather the event that allows diagnosis. The mass usually does not cause pain unless it compresses an adjacent nerve structure. The aim of this study is to systematically review the scientific literature in order to identify the most recent studies concerning malignant fibrous histiocytomas localized in oral soft tissues and report their main data. The main outcomes of this study concern the immunohistochemical, molecular, and clinical aspects of this pathology. A systematic review of articles in the electronic databases pubmed, Scopus, and Web of Science was performed. After the selection process, 11 studies met the inclusion criteria and were included in the review. The mean age of the patients was 50.8 years old. The lesions affected various parts of the oral cavity, showing predominantly storiform-pleomorphic patterns. All cases except one were treated with surgical resection and radiation therapy. Although some data emerged from this review, they remain limited to a few case reports. Further studies are necessary in order to standardize the approach to patients affected by oral malignant fibrous histiocytoma (MFH).

Undifferentiated Pleomorphic Sarcoma: Long-Term Follow-Up from a Large Institution

Purpose

Our study aimed to describe the clinical features of undifferentiated pleomorphic sarcoma (UPS) and identify the predictors of poor outcomes.

Patients and methods

The clinicopathological variables and treatment strategies of 100 UPS patients who underwent surgical resections at a single institution between November 2004 and July 2016 were reviewed. Kaplan–Meier and Cox regression method were conducted for survival analysis.

Results

The median follow-up time was 94 months (range, 1.5–154 months). R0 resection was applied for 72 cases, and the median tumor size was 5.75cm (range, 1–30cm). Tumor grades of 45 patients were intermediate grade (G2), and 54 patients were with advanced stage (stage III/IV). Twenty-seven patients presented with tumors involving important structures, in which the nerve was the most frequently invaded structure (n=12). During the follow-up, 40 patients suffered from postoperative local recurrence, and distant metastasis was observed in 25 patients which mainly metastasized to the lung (n=14). The 5-year OS rate, 5-year LRFS rate, and 5-year MFS rate was 53%, 55%, and 70%, respectively. Multivariate analysis revealed that tumor presentation, tumor size, and important structures involved (p=0.033, p=0.004, and p=0.033, respectively) were independent prognostic factors associated with OS. Meanwhile, age, resection quality and tumor grade were independent prognostic factors for LRFS (p=0.033, p=0.045, and p=0.007, respectively) and tumor depth was significantly associated with MFS (p=0.050) in multivariate analysis.

Conclusion

Primary treatment of UPS should be conducted by experts in large sarcoma center. Wide surgical margin provides sufficient control of the disease recurrence.

The Outcome of Patients With Localized Undifferentiated Pleomorphic Sarcoma of the Lower Extremity Treated at Stanford University

BACKGROUND

As a diagnosis of exclusion, Undifferentiated Pleomorphic Sarcoma (UPS) has unclear clinical characteristics. The objective of this retrospective cohort study is to investigate which clinical and prognostic factors of primary lower-extremity UPS will determine failure.

METHODS

We retrospectively reviewed 55 primary lower-extremity UPS cases treated at Stanford between 1998 and 2015. Overall Survival (OS) and Disease-Free Survival (DFS) curves were calculated. Univariate Fisher's Exact Tests were used to examine relationships between disease recurrence, treatment, patient factors, tumor characteristics, and surgical margins.

RESULTS

5-year DFS and OS rates were 60% (95% CI, 45%-72%) and 68% (95% CI, 53%-79%), respectively. The 5-year DFS rate for patients with positive margins was 33.3% (95% CI, 5%-68%) compared with 63% (95% CI, 47%-76%) for patients with negative margins. (Log-rank, P=0.03). The OS rate for those with disease recurrence was 42% % (95% CI, 16%-67%) compared with 76% (95% CI, 59%-87%) for patients who did not have disease recurrence (log-rank, P=0.021). Local failure occurred more frequently with omission of radiation therapy (Fisher's exact test, P=0.009).

CONCLUSIONS

Positive surgical margins are an important prognostic factor for predicting relapse in UPS. Relapse of any kind led to worse OS. Radiation therapy improved local control of disease but had no statistically significant effect on DFS, highlighting the need for improved diagnostics to identify those at highest risk for hematogenous metastasis and for selection of patients for adjuvant systemic treatment.

TP53 in bone and soft tissue sarcomas

Genomic and functional study of existing and emerging sarcoma targets, such as fusion proteins, chromosomal aberrations, reduced tumor suppressor activity, and oncogenic drivers, is broadening our understanding of sarcomagenesis. Among these mechanisms, the tumor suppressor p53 (TP53) plays significant roles in the suppression of bone and soft tissue sarcoma progression. Although mutations in TP53 were thought to be relatively low in sarcomas, modern techniques including whole-genome sequencing have recently illuminated unappreciated alterations in TP53 in osteosarcoma. In addition, oncogenic gain-of-function activities of missense mutant p53 (mutp53) have been reported in sarcomas. Moreover, new targeting strategies for TP53 have been discovered: restoration of wild-type p53 (wtp53) activity through inhibition of TP53 negative regulators, reactivation of the wtp53 activity from mutp53, depletion of mutp53, and targeting of vulnerabilities in cells with TP53 deletions or mutations. These discoveries enable development of novel therapeutic strategies for therapy-resistant sarcomas. We have outlined nine bone and soft tissue sarcomas for which TP53 plays a crucial tumor suppressive role. These include osteosarcoma, Ewing sarcoma, chondrosarcoma, rhabdomyosarcoma (RMS), leiomyosarcoma (LMS), synovial sarcoma, liposarcoma (LPS), angiosarcoma, and undifferentiated pleomorphic sarcoma (UPS).

PRDM10-rearranged Soft Tissue Tumor: A Clinicopathologic Study of 9 Cases

Gene fusion transcripts containing PRDM10 were recently identified in low-grade undifferentiated pleomorphic sarcomas (UPS). Here, we describe the morphologic and clinical features of 9 such tumors from 5 men and 4 women (age: 20 to 61 y). Three cases had previously been diagnosed as UPS, 3 as superficial CD34-positive fibroblastic tumor (SCD34FT), 2 as pleomorphic liposarcoma, and 1 as pleomorphic hyalinizing angiectatic tumor. The tumors were located in the superficial and deep soft tissues of the thigh/knee region (4 cases), shoulder (2 cases), foot, trunk, and perineum (1 case each) ranging in size from 1 to 6 cm. All showed poorly defined cellular fascicles of pleomorphic cells within a fibrous stroma with frequent myxoid change and a prominent inflammatory infiltrate. All displayed highly pleomorphic nuclear features, but a low mitotic count. Most tumors were well circumscribed. One of 9 tumors recurred locally, but none metastasized. Immunohistochemically, all were CD34 and showed nuclear positivity for PRDM10; focal positivity for cytokeratins was seen in 5/6 cases. PRDM10 immunoreactivity was evaluated in 50 soft tissue tumors that could mimic PRDM10-rearranged tumors, including 4 cases exhibiting histologic features within the spectrum of SCD34FT. Except for 2/6 pleomorphic liposarcomas and 1/4 myxofibrosarcomas, other tumors did not show nuclear positivity but displayed weak to moderate cytoplasmic immunoreactivity. In conclusion, PRDM10-rearranged soft tissue tumor is characterized by pleomorphic morphology and a low mitotic count. Its morphologic spectrum overlaps with SCD34FT. Clinical features of this small series suggest an indolent behavior, justifying its distinction from UPS and other sarcomas.

PET in the Diagnostic Management of Soft Tissue Sarcomas of Musculoskeletal Origin

Soft tissue sarcomas (STSs) account for less than 1% of adult solid tumors and about 7% of pediatric malignancies, causing 2% of cancer-related deaths. With the advent of PET-computed tomography (CT), the value of (18) fluorine-2-fluoro-2-deoxy-d-glucose (FDG) PET imaging to improve the management of STSs has been explored. FDG PET imaging has been found useful in restaging and treatment response assessment. This article reviews current knowledge and application of FDG PET-CT in initial diagnosis, staging, restaging, treatment response monitoring, and prognosis, with a brief overview of the most common histologic subtypes of STS.

Soft Tissue Sarcoma Cancer Stem Cells: An Overview

Soft tissue sarcomas (STSs) are an uncommon group of solid tumors that can arise throughout the human lifespan. Despite their commonality as non-bony cancers that develop from mesenchymal cell precursors, they are heterogeneous in their genetic profiles, histology, and clinical features. This has made it difficult to identify a single target or therapy specific to STSs. And while there is no one cell of origin ascribed to all STSs, the cancer stem cell (CSC) principle—that a subpopulation of tumor cells possesses stem cell-like properties underlying tumor initiation, therapeutic resistance, disease recurrence, and metastasis—predicts that ultimately it should be possible to identify a feature common to all STSs that could function as a therapeutic Achilles' heel. Here we review the published evidence for CSCs in each of the most common STSs, then focus on the methods used to study CSCs, the developmental signaling pathways usurped by CSCs, and the epigenetic alterations critical for CSC identity that may be useful for further study of STS biology. We conclude with discussion of some challenges to the field and future directions.

Subclassification of pleomorphic sarcomas: How and why should we care?

Pleomorphic sarcomas are a heterogeneous group of mesenchymal neoplasms with widely varied clinical behavior but overlapping histologic appearances. The following guidelines are helpful when approaching the diagnosis of a pleomorphic sarcoma. (1) Be aware of the relative incidence of the various sarcoma types: several pleomorphic sarcomas are relatively common (e.g., dedifferentiated liposarcoma and undifferentiated pleomorphic sarcoma), whereas others are exceptionally rare. (2) Pay attention to anatomic location: some pleomorphic sarcomas have a predilection for somatic soft tissues, especially the thigh (e.g., undifferentiated pleomorphic sarcoma, pleomorphic liposarcoma, pleomorphic rhabdomyosarcoma), whereas other pleomorphic sarcomas most often arise in the retroperitoneum (e.g., dedifferentiated liposarcoma). (3) Carefully sample the resection specimen, paying particular attention to areas with differences in gross appearances (e.g., fleshy, fibrous, mucoid, or gritty). (4) Search for histologic clues (i.e., myxoid stroma, lipoblasts, and osteoid matrix, in order to diagnose myxofibrosarcoma, pleomorphic liposarcoma, and extraskeletal osteosarcoma, respectively); these critical diagnostic features may be limited in extent. (5) Apply immunohistochemistry judiciously, after generating a differential diagnosis; always exclude metastatic sarcomatoid carcinoma and melanoma before diagnosing a pleomorphic sarcoma. This review will present an approach to the diagnosis of pleomorphic sarcomas, emphasizing differential diagnosis and the application of ancillary studies (immunohistochemistry and FISH), when relevant.

Undifferentiated Pleomorphic Sarcoma Metastatic to the Orbit

Undifferentiated pleomorphic sarcoma is a malignancy of mesenchymal origin, which was previously known as malignant fibrous histiocytoma. It is known to occur on rare occasion as a primary orbital tumor, but no known cases of metastatic orbital involvement have been reported since 2002, when the reclassification of these tumors took place. The authors report a patient who presented with a metastasis to the left orbit 2 years after undergoing treatment of a high-grade undifferentiated pleomorphic sarcoma of the right thigh. Histopathology of the orbital mass was similar to the primary tumor biopsy prior to neoadjuvant chemotherapy and radiation. The appearance was markedly altered in the subsequent excisional tissue, which showed treatment changes. Immunohistochemistry and genetic testing also supported the metastatic nature of the orbital lesion. The patient's tumor progressed rapidly despite systemic targeted therapy and orbital exenteration was performed. At 2 years follow up, the patient remained without evidence of tumor recurrence in the socket.

Undifferentiated Pleomorphic Sarcoma of Liver: Case Report and Review of the Literature

Undifferentiated pleomorphic sarcoma (UPS), previously known as malignant fibrous histiocytoma (MFH), is rarely reported in the liver as a primary site. We report a case of a previously healthy 56-year-old male, who presented with abdominal pain and jaundice. The patient was originally diagnosed with cholecystitis, treated with cholecystectomy, which was complicated by abdominal abscess. One week following discharge, the patient was readmitted with fever, chills, and leukocytosis. Computed tomography (CT) guided liver biopsies demonstrated an epithelioid to spindle cell neoplasm with markedly atypical nuclei and prominent necrosis infiltrating between hepatocytes. Immunohistochemical studies were negative for epithelial, melanocytic, and hematolymphoid differentiation. Positron emission tomography (PET) was performed, which showed a single markedly hypermetabolic central hepatic mass (14 x 8.5 x 8.5 cm) with likely central necrosis, consistent with primary malignancy. The patient was treated with one cycle of chemotherapy (doxorubicin and ifosfamide), refusing additional cycle due to medication side effects. The patient subsequently succumbed to complications associated with the malignancy and died within 19 days of diagnosis.

Undifferentiated Pleomorphic Sarcoma of Pancreas: A Case Report and Review of the Literature for the Last Updates

The most prevalent type of soft tissue sarcoma is undifferentiated pleomorphic sarcoma (UPS) or previously known as malignant fibrous histiocytoma. It accounts over 20% of all soft tissue sarcomas and occurs most frequently in the extremities, trunk, and retroperitoneum. However, it has been rarely observed in the digestive system. Pancreas sarcoma represents less than 1% of all pancreatic tumors, and primary UPS of the pancreas is even rarer. It exhibits high recurrence and poor prognosis. In this case, a 72-year-old woman with a UPS tumor which was located in the pancreas head and neck without adhesion to the retroperitoneum will be discussed.

Combined chemoradiation for head and neck region myxofibrosarcoma of the maxillary sinus

Aims and background

Adult sarcomas of the head and neck region (HNSs) are considered a rare clinicopathological entity. They account for only 2–15% of all adult sarcomas and for less than 1% of all head and neck malignancies. The preferred initial treatment option is wide surgical excision. Whenever surgery is considered infeasible, a frontline combined-modality approach including radiotherapy and chemotherapy might be proposed. We here report on a case of localized sarcoma of the maxillary sinus treated with induction chemotherapy and subsequent intensity-modulated radiation therapy (IMRT), achieving a persistent complete remission status.

Methods

A 66-year-old man was referred to our institution hospital for left-sided facial pain with swollen left cheek and ipsilateral facial palsy. Magnetic resonance imaging showed a mass within the left maxillary sinus extending to the orbital floor and adjacent alveolar bones. Histological examination of the biopsy specimen demonstrated a myxofibrosarcoma. The patient underwent induction chemotherapy with gemcitabine 900 mg/m2 (days 1–8) and taxotere 80 mg/m2 every 3 weeks for 3 cycles and sequential simultaneous integrated boost (SIB) IMRT up to a total dose of 70 Gy/35 fractions to the macroscopic disease with 59.5 Gy/35 fractions to the level IB-II lymph nodes in the left neck.

Results

Treatment was well tolerated with mild acute toxicity. Complete remission was achieved at restaging MRI 6 months after the end of the combined modality approach. The patient remains in complete, unmaintained clinical and instrumental complete remission 18 months after treatment, with no late side effects.

Conclusion

Combination therapy with induction chemotherapy and sequential SIB-IMRT could therefore be a promising modality for head and neck sarcomas, allowing for simultaneous tumor control and normal tissue sparing.

Retrovesical malignant fibrous histiocytoma: a rare tumor

Malignant fibrous histiocytoma (MFH) originating from the retrovesical space is a very rare tumour. A 61-year-old man presented to our hospital with complaints of retention of urine and burning sensation during micturition since 6 months. CT scan abdomen showed a large retrovesical mass between the urinary bladder and rectum, measuring 11×9×12 cm, displacing the urinary bladder. Serum PSA (Prostate Specific Antigen) value was within normal range. Biopsy from retrovesical mass and immunohistochemistry was suggestive of MFH. Wide excision of the retrovesical mass was done. Histopathology confirmed the diagnosis of MFH. He received adjuvant radiotherapy. He is on regular follow-up since the last 2 years after radiotherapy with no signs and symptoms of disease recurrence.

miR-152 down-regulation is associated with MET up-regulation in leiomyosarcoma and undifferentiated pleomorphic sarcoma

PURPOSE

Highly aggressive adult soft tissue sarcomas (STS), i.e., leiomyosarcomas (LMS) and undifferentiated pleomorphic sarcomas (UPS), present complex genomic anomalies and overall 5-year survival rates of 20 to 40%. Here, we aimed to identify new biomarkers that may be employed to improve the treatment of non-translocation STS patients. We validated 12 miRNAs implicated in tumor development using primary STS samples and selected miR-152 for further analysis in STS-derived cell lines.

METHODS

59 primary STS samples (27 LMS and 32 UPS) and 10 matched normal control tissues were included in the study, as well as 3 STS-derived cell lines (HT1080, SW872 and SKLMS1) and a normal control mesenchymal cell line (hMSC). miRNA expression analyses were performed using a TaqMan microRNA Array platform and qRT-PCR (miR-152), respectively. The expression levels of the putative miR-152 targets MET and KIT were assessed using qRT-PCR and immunohistochemistry on tissue microarrays, respectively. In addition, various functional analyses were performed before and after miR-152 transfection into SKLMS1 cells.

RESULTS

We found that 12 pre-selected miRNAs were down-regulated in primary STS tumor samples compared to its normal control samples. A statistically significant miR-152 down-regulation was found to be accompanied by high MET and KIT mRNA levels in both the primary samples and the STS-derived cell lines tested. miR-152 transfection in SKLMS1 cells led to a reduction in KIT and MET mRNA and protein levels which, in turn, was associated with a transient down-regulation of the PI3K/AKT pathway, a transient decrease in cell growth, and a transient increase in both apoptotic and S-phase cells.

CONCLUSIONS

Our data indicate that over-expression of MET and KIT in primary STS samples and its derived cell lines is associated with miR-152 down-regulation. This shift may play a role in STS development and, thus, may be used to identify patients at risk. The effect of MET down-regulation on downstream signaling pathways, such as the PI3K/AKT pathway, may provide a basis for the future design of novel STS treatment strategies.

Characterization of a Rat Subcutaneous Malignant Fibrous Histiocytoma and Its Tumor Lines, with Reference to Histiocytic Features

Malignant fibrous histiocytoma (MFH) is regarded as soft tissue-derived undifferentiated pleomorphic sarcoma, of which the histogenesis remains to be proven. To investigate the cellular characteristics, a homotransplantable tumor line (KJ) was established from a spontaneous MFH that developed in the subcutis of an aged F344 rat. KJ tumors have been produced in syngeneic rats by serial subcutaneous implantation of tissue fragments. The original and KJ tumors consisted of oval and fusiform cells arranged in interlacing bundles with fibrous stroma. Occasional giant cells with bizarre nuclei were observed. Enzyme/immunohistochemically, neoplastic cells reacted to ED1 and ED2 (antibodies specific for rat histiocytes/macrophages), and showed a positive reaction to vimentin and lysosomal enzyme markers such as acid phosphatase (ACP) and nonspecific esterase (Non-SE). Electron microscopically, neoplastic cells possessed lysosomal granules in cytoplasm. A cloned cell line (KJ-A) was isolated from a KJ tumor. KJ-A cells showed positive reactions to ED1, ED2, ACP, and Non-SE, and had cytoplasmic lysosomal granules. Tumors induced by KJ-A cells exhibited histologic and enzyme/immunohistochemical findings similar to those of KJ tumors. Lipopolysaccharide (LPS) treatment increased the number of ED1-positive cells and the expression of tumor necrosis factor-α mRNA by reverse transcription-polymerase chain reaction. Collectively, it is likely that rat MFH cells originally possess histiocyte/macrophage-like features that may be enhanced by LPS. Because tumor lines are useful for in vivo and in vitro studies concerning different characteristics of the original neoplasms. KJ and KJ-A should prove useful for studies concerning the morphogenesis of MFH.

Special AT-rich sequence-binding protein 2 (SATB2) expression is sensitive but may not be specific for osteosarcoma as compared with other high-grade primary bone sarcomas

AIMS

The diagnosis of osteosarcoma, although important for eligibility in clinical trials and proper therapy, may be challenging when no bone or osteoid matrix is identified on biopsy. Therefore, other adjunct tests have been sought to help confirm the diagnosis. Special AT-rich sequence-binding protein 2 (SATB2) has been shown as a reliable marker of osteoblastic differentiation. The aim of this study was to examine SATB2 expression in osteosarcomas and other primary bone sarcomas, in order to evaluate its diagnostic utility in discriminating osteogenic from non-osteogenic sarcomas.

METHODS AND RESULTS

Forty-eight pretreated osteosarcoma biopsies, including 26 whole-section cases and 22 tumours on tissue microarrays, and 36 non-osteogenic bone sarcomas were evaluated. Forty-five of 48 (94%) osteosarcomas showed nuclear immunoreactivity for SATB2 (all whole-slide sections showed expression). Positive SATB2 expression was observed in 11 of 22 (50%) undifferentiated pleomorphic sarcomas (UPSs), and in five of 11 (45%) fibrosarcomas; expression was absent in two pleomorphic rhabdomyosarcomas and in the one leiomyosarcoma. The sensitivity of SATB2 for osteosarcoma was 94%, and the specificity was 55%. Stronger-intensity staining was observed in osteosarcoma (P < 0.0001).

CONCLUSIONS

SATB2 is a sensitive marker for osteosarcoma; however, it is not specific, with expression being observed in other high-grade primary bone sarcomas. Intriguingly, the lack of specificity may suggest that the undifferentiated sarcomas (UPSs and fibrosarcomas) with SATB2 expression actually represent osteosarcomas that produce too little matrix to be detected with routine sampling or consist of osteoblast precursors that do not synthesize matrix.

Evaluation of prognostic factors in localized high-grade undifferentiated pleomorphic sarcoma: report of a multi-institutional experience of Anatolian Society of Medical Oncology

Most data on prognostic factors for patients with high-grade undifferentiated pleomorphic sarcoma (HGUPS) is obtained from analyses of soft tissue sarcomas. The purpose of this study was to evaluate the clinicopathologic features and their impact on outcomes specifically in patients diagnosed with HGUPS. In this multicenter trial, we retrospectively analyzed 112 patients who were diagnosed and treated at 12 different institutions in Turkey. We collected data concerning the patients, tumor characteristics, and treatment modalities. There were 69 males (61.6 %) and 43 females (38.4 %). Median age was 56 years (19-90). The most common anatomic site of tumor origin was the upper extremity. Pleomorphic variant was the predominant histological subtype. Median tumor size was 8.2 cm (0.6-30 cm). Tumors were mainly deeply seated (57.1 %). Fifty-seven patients (50.9 %) were stage II and the remainder were stage III at the time of diagnosis. Median follow-up was 30 months (2-160). The primary site of distant metastasis was the lung (73.5 %) and the second most common site was the liver (11.7 %). The 5-year overall survival, distant metastasis-free survival, and local recurrence-free survival rates were 56.3, 53.4, and 67.2 %, respectively. Multivariate analysis showed that Eastern Cooperative Oncology Group (ECOG) performance score of II (p = 0.033), deep tumor location (p = 0.000), and development of distant metastasis (p = 0.004) were negatively correlated with overall survival, and perioperative radiotherapy and negative microscopic margins were significant factors for local control rates (p = 0.000 for each). Deep tumor location (p = 0.003) was the only adverse factor related to distant metastasis-free survival. Deep tumor location, ECOG performance score of II, and development of distant metastasis carry a poor prognostic implication on overall survival. These will aid clinicians in predicting survival and treatment decision.

Recurrent PRDM10 gene fusions in undifferentiated pleomorphic sarcoma

PURPOSE

Undifferentiated pleomorphic sarcoma (UPS) is defined as a sarcoma with cellular pleomorphism and no identifiable line of differentiation. It is typically a high-grade lesion with a metastatic rate of about one third. No tumor-specific rearrangement has been identified, and genetic markers that could be used for treatment stratification are lacking. We performed transcriptome sequencing (RNA-Seq) to search for novel gene fusions.

EXPERIMENTAL DESIGN

RNA-Seq, FISH, and/or various PCR methodologies were used to search for gene fusions and rearrangements of the PRDM10 gene in 84 soft tissue sarcomas.

RESULTS

Using RNA-Seq, two cases of UPS were found to display novel gene fusions, both involving the transcription factor PRDM10 as the 3' partner and either MED12 or CITED2 as the 5' partner gene. Further screening of 82 soft tissue sarcomas for rearrangements of the PRDM10 locus revealed one more UPS with a MED12/PRDM10 fusion. None of these genes has been implicated in neoplasia-associated gene fusions before.

CONCLUSIONS

Our results suggest that PRDM10 fusions are present in around 5% of UPS. Although the fusion-positive cases in our series showed the same nuclear pleomorphism and lack of differentiation as other UPS, it is noteworthy that all three were morphologically low grade and that none of the patients developed metastases. Thus, PRDM10 fusion-positive sarcomas may constitute a clinically important subset of UPS.

Undifferentiated Pleomorphic Sarcoma in Mandible

Undifferentiated pleomorphic sarcoma (UPS), previously known as malignant fibrous histiocytoma, occurs commonly in the soft tissues in adult, but is rare in the maxillofacial region. It consists of undifferentiated mesenchymal tumor cells resembling histiocytes and fibroblasts. The purpose of this article is to report a case of UPS in the mandible. A 44-year-old patient presented with a painful growing mass in the mandible of two months’ duration. Computed tomography and positron emission tomography-computed tomography revealed an ill-defined heterogenous, hypermetabolic mass about 4 cm in size in the left mandible invading adjacent soft tissues. A left mandiblulectomy and reconstruction with a fibular free flap were performed. Immunohistochemical study gave a diagnosis of UPS. The patient was referred for adjuvant chemotherapy after surgical removal of the tumor.

Primary osseous inflammatory malignant fibrous histiocytoma masquerading as chronic osteomyelitis

Inflammatory malignant fibrous histiocytoma, in addition to a mass lesion, may present with fever and other constitutional symptoms, mimicking an infectious process. This article presents an extremely rare and unique case of primary osseous inflammatory malignant fibrous histiocytoma, highlighting retrospectively the subtle clinical, radiologic, and pathologic features that can suggest this diagnosis. A 63-year-old woman with a history of nephrectomy for right kidney tuberculosis 20 years ago presented with slowly increasing left hip pain for 6 months. The relatively benign-appearing radiograph and biopsy report of chronic inflammation resulted in curettage and nailing of the lesion. The pathologic diagnosis was chronic osteomyelitis, but culture findings for bacteria and tuberculosis were negative. The patient remained well until 4 months later, when left thigh pain returned with fever and leukocytosis (white blood cell count as high as 20.7×10(9)/L, 80% neutrophils). No source of infection was localized. The patient showed no response to broad-spectrum antibiotics and antituberculous drugs. Radiographs showed substantial enlargement of the femoral lesion and extraosseous extension; biopsy results and review of previous histopathologic findings led to a diagnosis of inflammatory malignant fibrous histiocytoma. The fever gradually resolved and the white blood cell count returned to normal within a few days after segmental resection of the proximal femur tumor and its soft tissue extension. However, deep venous thrombosis developed, resulting in left foot ischemia and toe gangrene, necessitating left below-the-knee amputation. Disseminated metastasis occurred 3 months after tumor resection. The patient declined further aggressive treatment and died 13 months after initial presentation.

MFH and high-grade undifferentiated pleomorphic sarcoma-what's in a name?

BACKGROUND AND OBJECTIVES

In 2002, with the advent of better classification techniques, the World Health Organization declassified malignant fibrous histiocytoma (MFH) as a distinct histological entity in favor of the reclassified entity high-grade undifferentiated pleomorphic sarcoma (HGUPS). To date, no study has evaluated comparative outcomes between patients designated historically in the MFH group and those classified in the new HGUPS classification. Our goal was to determine the presence of clinical prognostic implications that have evolved with this new nomenclature.

METHODS

Sixty-eight patients were retrospectively evaluated between January 1998 and December 2007. Forty-five patients diagnosed with MFH between 1998 and 2003 were compared to 23 patients in the HGUPS group, from 2004 to 2007. Primary prognostic outcomes assessed included overall survival, metastatic-free, and local recurrence-free survival.

RESULTS

Five-year survivorship between MFH and HGUPS populations, using Kaplan-Meier or competing risk methods, did not show statistical difference for overall survival (60% vs. 74%, P=0.36), 5-year metastasis-free survival (31% vs. 26%, P=0.67), or local recurrence-free survival (13% vs. 16%, P=0.62).

CONCLUSION

Despite new classification nomenclature, there appears to be no identifiable prognostic implications for sarcomas that remain in the unclassifiable HGUPS group, as compared to the previously accepted MFH group.

High IGF2 and FGFR3 are associated with tumour progression in undifferentiated pleomorphic sarcomas, but EGFR and FGFR3 mutations are a rare event

AIM

Pleomorphic undifferentiated sarcomas (formerly known as malignant fibrous histiocytomas) are recognised by the actual WHO classification as an undifferentiated, unclassifiable category of pleomorphic sarcomas which show no definable line of differentiation and are still a diagnosis of exclusion. Therefore, diagnostic, prognostic and therapeutic options of these tumours are urgently needed.

METHODS

Three hundred and twenty-seven spindle cell tumours of a German consultation and reference centre of soft tissue tumours consisting of 200 undifferentiated pleomorphic sarcomas (UPS), 45 low-grade sarcomas (10 low-grade fibromyxoid sarcomas, 32 low-grade myofibroblastic sarcomas and three myxoinflammatory fibroblastic sarcomas) and 82 tumours of the fasciitis family were revisited. The specimens were analysed immunohistochemically with distinct markers including tyrosine kinases and expression correlated with clinicopathological parameters. Additionally, mutational analysis was performed on specimens with high expression of EGFR and FGFR3.

RESULTS

At the protein level high IGF2 expression was observed in 86 %, FGFR3 (69 %), PDGFRA (62 %), PDGFRB (39 %), FGFR1 (8 %), EGFR (5 %), KDR/VEGFR2 (3 %), ALK (0 %) and high Ki67 (63 %) in UPS. High expressions of IGF2 and FGFR3 are significantly correlated with a higher grading (p = 0.023 and p = 0.016, respectively) and a high Ki67 index (p = 0.017 and p = 0.001, respectively). No mutations were found in the hot spots of tumour specimens with a high expression of EGFR gene (exons 18-21) and FGFR3 gene (exons 7, 10 and 15).

CONCLUSIONS

High expressions of IGF2 and FGFR3 are significantly associated with tumour progression, grading and Ki67 and might classify a subgroup of undifferentiated pleomorphic sarcoma. These markers might guide targeted therapies in these neoplasms.

Liposarcomas: diagnostic pitfalls and new insights

Liposarcomas represent the most common histotype among soft tissue sarcomas. However, liposarcomas in fact constitute a heterogeneous group of distinctive lesions that pose several diagnostic difficulties. The current World Health Organization classification of soft tissue and bone tumours recognizes four major liposarcoma subtypes: (i) atypical lipomatous tumour/well-differentiated liposarcoma; (ii) de-differentiated liposarcoma; (iii) myxoid liposarcoma; and (iv) pleomorphic liposarcoma. These four main subgroups are characterized by distinctive morphologies, unique genetic findings as well as distinct clinical behaviour. Accurate classification requires the integration of morphological, immunohistochemical and (in selected situations) genetic findings, and is essential for providing patients with the best available treatments. This review will focus upon the main diagnostic pitfalls encountered in the routine diagnosis of liposarcoma, underlining the diagnostic value of combining morphology with cytogenetics and molecular genetics.

A current perspective on the role for molecular studies in soft tissue tumor pathology

Soft tissue sarcomas represent an heterogenous group of malignancies. They represent a diagnostic challenge, and their accurate classification impact over treatment options. Sarcomas, similarly to hematologic neoplasm, often harbor relatively specific genetic aberrations, the recognition of which can be used to improved diagnostic accuracy. This review will focus on the clinical relevance of molecular analysis in soft tissue sarcomas, trying to elucidate its role as a diagnostic tool as well as a potential prognostic/predictive marker.

Inverse Relationship between Tumor Proliferation Markers and Connexin Expression in a Malignant Cardiac Tumor Originating from Mesenchymal Stem Cell Engineered Tissue in a Rat in vivo Model

Background: Recently, we demonstrated the beneficial effects of engineered heart tissues for the treatment of dilated cardiomyopathy in rats. For further development of this technique we started to produce engineered tissue (ET) from mesenchymal stem cells. Interestingly, we observed a malignant tumor invading the heart with an inverse relationship between proliferation markers and connexin expression.

Methods: Commercial CD54⁺/CD90⁺/CD34⁻/CD45⁻ bone marrow derived mesenchymal rat stem cells (cBM-MSC), characterized were used for production of mesenchymal stem-cell-ET (MSC-ET) by suspending them in a collagen I, matrigel-mixture and cultivating for 14 days with electrical stimulation. Three MSC-ET were implanted around the beating heart of adult rats for days. Another three MSC-ET were produced from freshly isolated rat bone marrow derived stem cells (sBM-MSC).

Results: Three weeks after implantation of the MSC-ETs the hearts were surgically excised. While in 5/6 cases the ET was clearly distinguishable and was found as a ring containing mostly connective tissue around the heart, in 1/6 the heart was completely surrounded by a huge, undifferentiated, pleomorphic tumor originating from the cMSC-ET (cBM-MSC), classified as a high grade malignant sarcoma. Quantitatively we found a clear inverse relationship between cardiac connexin expression (Cx43, Cx40, or Cx45) and increased Ki-67 expression (Cx43: p < 0.0001, Cx45: p < 0.03, Cx40: p < 0.014). At the tumor-heart border there were significantly more Ki-67 positive cells (p = 0.001), and only 2% Cx45 and Ki-67-expressing cells, while the other connexins were nearly completely absent (p < 0.0001).

Conclusion and Hypothesis: These observations strongly suggest the hypothesis, that invasive tumor growth is accompanied by reduction in connexins. This implicates that gap junction communication between tumor and normal tissue is reduced or absent, which could mean that growth and differentiation signals can not be exchanged.

MASL1: a neglected ROCO protein

The human ROCO proteins are a family of four proteins characterized by a conserved supradomain: a Ras-like GTPase domain. This domain consists of ROC (Ras of complex proteins) occurring in tandem with a COR (C-terminal of ROC) domain. Together, these proteins are linked to various pathologies including cancer and PD (Parkinson's disease). Despite an increasing research focus on these proteins, their functions in general, and their specific roles in disease, are still unknown. In the case of MASL1 (malignant fibrous histiocytoma amplified sequences with leucine-rich tandem repeats 1), a predicted oncoprotein in MFHs (malignant fibrous histiocytomas), there is a particular lack of information available in the literature. The aim of the present review is therefore to summarize the existing information on MASL1 and also to compile data that could be linked to MASL1 and thus help our understanding of this neglected ROCO protein.

Proliferative and non-proliferative lesions of the rat and mouse soft tissue, skeletal muscle and mesothelium

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in the soft tissues including skeletal muscle as well as the mesothelium of rats and mice. The standardized nomenclature of lesions presented in this document is also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as those induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for lesions in soft tissues, skeletal muscle and mesothelium in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists. (DOI: 10.1293/tox.26.1S; J Toxicol Pathol 2013; 26: 1S-26S).

Primary Malignant Fibrous Histiocytoma in Mediastinum: Imaging with (18)F-FDG PET/CT

Malignant fibrous histiocytoma (MFH) is the most common soft tissue tumor which often occurs in the extremities and the retroperitoneum. Primary mediastinal MFH is rare; thus, findings on (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) of mediastinal MFH have not been reported yet. We report herein the case of a 64-year-old man who was presented with a superior mediastinal mass. The mass showed intense (18)F-FDG uptake with central metabolic defect on PET/CT. The maximum standardized uptake value was 17.4. After tumor removal via median sternotomy, an MFH of the storiform-pleomorphic type was diagnosed on histopathologic examination. We present the first report of (18)F-FDG PET/CT imaging of MFH in the superior mediastinum.

From PTEN loss of expression to RICTOR role in smooth muscle differentiation: complex involvement of the mTOR pathway in leiomyosarcomas and pleomorphic sarcomas

Over the past decade, comprehensive genomic studies demonstrated that leiomyosarcomas and most of the tumors previously labeled as 'malignant fibrous histiocytomas' share complex karyotypes and genomic profiles, and can be referred to as 'sarcomas with complex genomics'. We recently reported a series of 160 sarcomas with complex genomics such as leiomyosarcomas, myxofibrosarcomas, pleomorphic liposarcomas/rhabdomyosarcomas and undifferentiated pleomorphic sarcomas. These tumors present with a frequent loss of chromosome 10 region encompassing the tumor suppressor gene PTEN. In the present study, we assessed PTEN genomic level and protein expression in this large series of sarcomas with complex genomics, as well as activation of downstream pathways. PTEN partial genomic loss was observed in only 46% of tumors, especially in well-differentiated leiomyosarcomas, whereas up to 68% of these tumors demonstrate a loss of protein expression on western blot analysis. Specific discrepancies in PTEN immunohistochemical results suggested bias in this latter technique. PTEN mutations were rare, with only 4 point mutations in the 65 samples studied. Subsequent activation of AKT and mTOR pathways was only observed in 2 out of 3 of PTEN-deleted tumors. On the other hand, RICTOR, a major component of the mTOR complex 2, was significantly overexpressed in well-differentiated leiomyosarcomas. These results, confirmed on tissue micro-array immunohistochemical analysis of 459 sarcomas, could suggest a link between RICTOR overexpression and leiomyosarcomas oncogenesis. As therapeutics directed against the mTOR pathway are assessed in sarcomas, RICTOR overexpression in sarcomas and its links to therapeutic response need to be assessed.

Morphological and Immunohistochemical Characterization of Sarcomatous Tumors in Wild-Type and Genetically Engineered Mice

Malignant soft tissue tumors are commonly observed in wild-type and gene-targeted mice. These tumors have different degrees of differentiation, cellularity, cellular atypia, nuclear pleomorphism, normal and abnormal mitosis, and giant tumor cells with enlarged polylobulated nuclei. They are often diagnosed as pleomorphic sarcoma, undifferentiated sarcoma, fibrosarcoma, malignant fibrous histiocytoma, sarcoma, or sarcoma, not otherwise specified. Pleomorphic sarcomas have no morphological differentiation toward a differentiated mesenchymal or other tumor type in hematoxylin and eosin–stained sections. With the use of immunohistochemistry, human and mouse, tumors associated with these broad nonspecific diagnoses can often be demonstrated to be of a specific cellular lineage. With mouse models being used to delineate the molecular mechanisms, pathogenesis, and cellular origin of human sarcomas, it will be necessary to correlate the morphological and cellular lineage and the molecular profiles of the pleomorphic tumors associated with these mouse models. The results presented here show that with the use of immunohistochemistry, the cellular lineage of many mouse tumors with pleomorphic features can be determined.

Primary pericardial sarcoma: a case report and a brief review

There are very few cases of primary pericardial sarcomas reported in the English literature. Pericardial tumors, like other cardiac tumors, are most likely to be metastatic in nature and are an extension of primary tumors from the surrounding structures. Sarcomas are the most common primary pericardial tumors. Surgical eradication of the tumor is considered to be the treatment of choice. We are presenting a case of a primary pericardial, high-grade pleomorphic undifferentiated sarcoma that was diagnosed at our institution. We discuss the available diagnostic modalities and also shed light on alternative therapies when patients are not ideal surgical candidates.

Undifferentiated high-grade pleomorphic sarcoma in a California sea lion (Zalophus californianus)

A tumour located in the pectoral region and the left front flipper was observed in a 29-year-old female California sea lion (Zalophus californianus) that died following signs of respiratory disease and inappetence. Metastases were present in the lung and adrenal gland. The histological pattern of the tumour was variable. In some areas the tumour consisted of pleomorphic fibroblast-like cells arranged in a storiform pattern, while in other areas it comprised oval or polygonal cells with round to oval nuclei and some bizarre cells arranged in an alveolar pattern. Occasionally, multinucleated giant cells were observed. Immunohistochemically, the neoplastic cells only expressed vimentin. On the basis of the microscopical and immunohistochemical features the tumour was diagnosed as an undifferentiated high-grade pleomorphic sarcoma. This type of neoplasm with disseminated involvement of other organs is rare in all species and has never been reported in California sea lions.

Malignant fibrous histiocytoma secondary to a traumatic hematoma

We present a case of malignant fibrous histiocytoma located in the region of the temple that corresponded to the main site of a traumatic hematoma. There are reports of malignant transformation triggered by different kinds of wounds, but the malignant transformation in a subcutaneous hematoma is rare. For chronic expanding hematoma, magnetic resonance imaging or biopsy is recommended in determining whether it is malignant, especially when the mass is growing rapidly.