Clear cell sarcoma-A review

Clinical characterization and therapeutic targeting of fusion genes in oncology

Gene fusions represent important oncogenic driver mutations resulting in aberrant cellular signaling. In up to 17% of all solid tumors at least one gene fusion can be identified. Precision therapy targeting fusion gene signaling has demonstrated effective clinical benefit. Advancements in clinically relevant next-generation sequencing and bioinformatic techniques have enabled expansion of therapeutic opportunity to subpopulations of patients with fusion gene expression. Clinically, tyrosine inhibitors have shown efficacy in treating fusion gene expressing cancers. Fusion genes are also clonal mutations, meaning it is a personal cancer target involving all cancer cells of that patient, not just a subpopulation of cancer cells within the cancer mass. Thus, both fusion signal disruption and immune signal targeting are effective therapeutic directions. This review discusses fusion gene targeting, therapeutic resistance, and molecular biomarkers.

Primary intraretinal clear cell sarcoma presenting as an amelanotic circumpapillary tumor

Purpose

To report a novel case of clear cell sarcoma presenting as an intraocular mass in a young adult female.

Observations

A 34-year-old female presented to the Retina Service as an emergency department referral for an intraocular lesion noted in the left eye. The patient endorsed progressively decreased vision in the left eye for three months duration. Fundus examination of the left eye was notable for a circumpapillary, retinal amelanotic mass with vitreous seeding. Due to concern for retinoblastoma and poor visual potential, the decision was made for primary enucleation. Initial histopathologic and immunohistochemical analyses demonstrated a primitive-appearing, epithelioid to spindled, intraretinal malignancy, with expression of all melanocytic markers by immunohistochemistry. Molecular genetic testing detected an EWSR1::ATF1 fusion. The patient was diagnosed with clear cell sarcoma of the eye and systemic work up revealed no additional disease burden.

Conclusions and importance

Clear cell sarcoma is a soft tissue sarcoma that can present within the eye and should be included in the differential diagnosis of amelanotic intraocular (intraretinal) tumors, including those in adults with clinical appearances similar to retinoblastoma.

Medical imaging for the diagnosis, recurrence and metastasis evaluation of clear cell sarcoma

Clear cell sarcoma (CCS) of soft tissue is extremely rare, accounting for approximately 1% of all soft tissue tumours. It is very difficult to diagnose CCS based on clinical manifestations. Magnetic resonance imaging (MRI) provides high-resolution images of soft tissues and pathological features such as mucus, necrosis, bleeding, and fat through high and low signals on T1 weighted image (T1WI) and T2 weighted image (T2WI). On the other hand, the paramagnetism of melanin in CCS shortens the relaxation time of T1 and T2, and high signal intensity on T1WI and low signal intensity on T2WI can be found. This is different from most other soft tissue sarcomas. At present, the treatment method for CCS is surgical resection. MRI can effectively display the tumour edge, extent of surrounding oedema, and extent of fat involvement, which is highly important for guiding surgical resection and predicting postoperative recurrence. As an invasive sarcoma, CCS has a high risk of metastasis. Regardless of the pathological condition of the resected tumour, MRI or computed tomography (CT) should be performed every 1-2 years to assess recurrence at the primary site and to screen for metastasis in the lungs, liver, and bones. If necessary, PET-CT can be performed to evaluate the overall condition of the patient.

Essential role of postoperative follow-up in the management of clear cell sarcoma

Clear cell sarcoma (CCS) is a rare melanocytic soft tissue sarcoma known for its propensity to metastasize to the lymph nodes and typically has an unfavorable prognosis. Currently, surgical resection is the primary treatment for localized CCS, while radiotherapy and chemotherapy are preferred for metastatic cases. The roles of adjuvant chemotherapy, radiotherapy, and lymph node dissection are controversial. Although immunotherapy has emerged as a promising avenue in CCS treatment research, there are no established clinical standards for postoperative follow-up. This editorial discusses a recent article by Liu et al, with a focus on current diagnostic modalities, treatment approaches, and the challenging prognosis associated with CCS. Our aim is to underscore the importance of long-term patient follow-up in CCS management.

Biological and therapeutic insights from animal modeling of fusion-driven pediatric soft tissue sarcomas

Survival for children with cancer has primarily improved over the past decades due to refinements in surgery, radiation and chemotherapy. Although these general therapies are sometimes curative, the cancer often recurs, resulting in poor outcomes for patients. Fusion-driven pediatric soft tissue sarcomas are genetically defined by chromosomal translocations that create a chimeric oncogene. This distinctive, almost 'monogenic', genetic feature supports the generation of animal models to study the respective diseases in vivo. This Review focuses on a subset of fusion-driven pediatric soft tissue sarcomas that have transgenic animal tumor models, which includes fusion-positive and infantile rhabdomyosarcoma, synovial sarcoma, undifferentiated small round cell sarcoma, alveolar soft part sarcoma and clear cell sarcoma. Studies using the animal models of these sarcomas have highlighted that pediatric cancers require a specific cellular state or developmental stage to drive tumorigenesis, as the fusion oncogenes cause different outcomes depending on their lineage and timing of expression. Therefore, understanding these context-specific activities could identify targetable activities and mechanisms critical for tumorigenesis. Broadly, these cancers show dependencies on chromatin regulators to support oncogenic gene expression and co-opting of developmental pathways. Comparative analyses across lineages and tumor models will further provide biological and therapeutic insights to improve outcomes for these children.

Navigating diagnostic challenges-distinguishing malignant melanoma and clear cell sarcoma of soft tissues: a case report and review of the literature

BACKGROUND

Within the spectrum of melanocytic-differentiated tumors, the challenge faced by pathologists is discerning accurate diagnoses, with clear cell sarcoma of soft tissues standing out as a rare and aggressive neoplasm originating from the neural crest. Accounting for 1% of all soft tissue sarcomas, clear cell sarcoma of soft tissues poses diagnostic complexities, often misidentified owing to its phenotypic resemblance to malignant melanoma. This chapter delves into the intricacies of clear cell sarcoma of soft tissues, its epidemiology, characteristic manifestations, and the imperative need for a comprehensive diagnostic approach involving immunohistochemical and molecular analyses.

CASE PRESENTATION

A compelling case unfolds as a 25-year-old male from Morocco, initially misdiagnosed with malignant melanoma, experiences tumor recurrence on the second toe. With no history of trauma or familial neoplasia, the patient's clinical journey is explored, emphasizing the importance of detailed clinical examinations and radiological assessments. The chapter elucidates the histopathological findings, immunohistochemical spectrum, and the correlation between clinical parameters and diagnostic inference, ultimately leading to metatarsal amputation. This clinical vignette highlights the multidimensional diagnostic process in soft tissue neoplasms, emphasizing the synergistic role of clinical, radiological, and histopathological insights.

CONCLUSION

The diagnostic challenges inherent in melanocytic-differentiated tumors, exemplified by the rarity of soft tissue clear cell sarcoma, underscore the essential role of an integrated diagnostic approach. This concluding chapter emphasizes the perpetual collaboration required across pathology, clinical medicine, and radiology for nuanced diagnostic precision and tailored therapeutic strategies. The rarity of these soft tissue malignancies necessitates ongoing interdisciplinary engagement, ensuring the optimization of prognosis and treatment modalities through a comprehensive understanding of the diagnostic intricacies presented by clear cell sarcoma of soft tissues.

A Comparison of Clear Cell Sarcoma to Jaw and Salivary Tumors Bearing EWS Fusions

OBJECTIVE

To review tumors identified as "clear cell sarcoma" in order to determine similarities to the rare EWS fusion positive jaw and salivary gland tumors clear cell odontogenic carcinoma (CCOC) and clear cell carcinoma of the salivary gland (CCC).

METHODS

PubMed was used to collect all reports of clear cell sarcoma (CCS). Search parameters were "clear cell sarcoma" and "CCS." References in the publications were screened and cross-referenced. Data extracted included demographic characteristics, presenting signs and symptoms, radiographic findings, histological and immunohistochemical features and known molecular/genetic aberrations.

RESULTS

Clear cell sarcoma has several similarities to CCOC and CCC. All three tumor types have similar histologic appearances including the presence of clear cells, as well as similar genetic profiles in that all harbor an EWSR1-CREB family fusions. Additionally, these tumors appear in soft tissue as well as bone, and can have a prolonged clinical course. CCS can appear anywhere in the body, including the head and neck region. All three tumors appear to have a predilection to women, although CCS may have a slight younger age of onset as compared to CCOC and CCC (3rd vs 5th decade of life, respectively).

CONCLUSION

Gaining a better understanding of the similarities and differences between these three tumors may lead to a better understanding of each one.

EWSR1::ATF1 Orchestrates the Clear Cell Sarcoma Transcriptome in Human Tumors and a Mouse Genetic Model

Clear cell sarcoma (CCS) is a rare, aggressive malignancy that most frequently arises in the soft tissues of the extremities. It is defined and driven by expression of one member of a family of related translocation-generated fusion oncogenes, the most common of which is EWSR1::ATF1. The EWSR1::ATF1 fusion oncoprotein reprograms transcription. However, the binding distribution of EWSR1::ATF1 across the genome and its target genes remain unclear. Here, we interrogated the genomic distribution of V5-tagged EWSR1::ATF1 in tumors it had induced upon expression in mice that also recapitulated the transcriptome of human CCS. ChIP-sequencing of V5-EWSR1::ATF1 identified previously unreported motifs including the AP1 motif and motif comprised of TGA repeats that resemble GGAA-repeating microsatellites bound by EWSR1::FLI1 in Ewing sarcoma. ChIP-sequencing of H3K27ac identified super enhancers in the mouse model and human contexts of CCS, which showed a shared super enhancer structure that associates with activated genes.

The current management of clear cell sarcoma

Clear cell sarcoma (CCS) is a rare melanocytic soft tissue sarcoma with a high propensity for lymphatic metastasis and poor prognosis. It is characterized by the translocation of t (12;22), resulting in the rearrangement of the EWSR1 gene and overexpression of MET. Despite improvements in the diagnosis and treatment of soft tissue sarcomas, the management of CCSs remains challenging owing to their rarity, unique biological behaviour and limited understanding of their molecular pathogenesis. The standard treatment for localized CCSs is surgical excision with negative margins. However, there is an ongoing debate regarding the role of adjuvant chemotherapy, radiotherapy and lymphadenectomy in the management of this disease. CCSs are usually resistant to conventional chemotherapy. Targeted therapies, such as sunitinib and MET inhibitors, may provide promising results. Immunotherapy, particularly immune checkpoint inhibitors, is currently under investigation as a potential treatment option for CCSs. Further research is needed to better understand the biology of CCSs and develop effective therapeutic strategies. The purpose of this review is to provide a comprehensive overview of current knowledge and advances in the diagnosis and treatment of CCSs.

Primary angiomatoid fibrous histiocytoma of the mandible with EWSR1-ATF1 fusion in an adult patient: case report and review of literature

OBJECTIVE

We report our diagnosis of a rare case of primary angiomatoid fibrous histiocytoma in the mandible of a 42-year-old male using next-generation sequencing to detect disease-specific EWSR1-ATF1 fusion.

STUDY DESIGN

After the initial cone beam computerized tomography scan and reconstruction, we performed immunohistochemical staining and fluorescence in situ hybridization analysis on tissue samples to detect EWSR1 gene rearrangement. For the final diagnosis, we performed next-generation sequencing to detect disease-specific EWSR1-ATF1 fusion.

RESULTS

FISH analysis showed approximately 55% of tumor cells with mostly isolated red signals, as well as several split red-green signals, indicating the presence of EWSR1 gene rearrangement. Next-generation sequencing analysis identified an EWSR1 exon9-ATF1 exon4 fusion, a diagnostic biomarker of angiomatoid fibrous histiocytoma (AFH). Based on the findings, we diagnosed primary AFH derived from the mandible.

CONCLUSIONS

Next-generation sequencing is a powerful methodology for detecting disease-specific EWSR1-ATF1 fusion and diagnosing primary angiomatoid fibrous histiocytoma.

Gene fusions in superficial mesenchymal neoplasms: Emerging entities and useful diagnostic adjuncts

Cutaneous mesenchymal neoplasms are diagnostically challenging because of their overlapping morphology, and, often, the limited tissue in skin biopsy specimens. Molecular and cytogenetic techniques have identified characteristic gene fusions in many of these tumor types, findings that have expanded our understanding of disease pathogenesis and motivated development of useful ancillary diagnostic tools. Here, we provide an update of new findings in tumor types that can occur in the skin and superficial subcutis, including dermatofibrosarcoma protuberans, benign fibrous histiocytoma, epithelioid fibrous histiocytoma, angiomatoid fibrous histiocytoma, glomus tumor, myopericytoma/myofibroma, non-neural granular cell tumor, CIC-rearranged sarcoma, hybrid schwannoma/perineurioma, and clear cell sarcoma. We also discuss recently described and emerging tumor types that can occur in superficial locations and that harbor gene fusions, including nested glomoid neoplasm with GLI1 alterations, clear cell tumor with melanocytic differentiation and ACTIN::MITF translocation, melanocytic tumor with CRTC1::TRIM11 fusion, EWSR1::SMAD3-rearranged fibroblastic tumor, PLAG1-rearranged fibroblastic tumor, and superficial ALK-rearranged myxoid spindle cell neoplasm. When possible, we discuss how fusion events mediate the pathogenesis of these tumor types, and we also discuss the related diagnostic and therapeutic implications of these events.

Undifferentiated pleomorphic sarcoma of the breast with neoplastic fever: case report and genomic characterization

PURPOSE

Primary breast sarcomas are extraordinary rare, in particular undifferentiated pleomorphic sarcoma (UPS). UPS with neoplastic fever (UPS-NF) of the breast has not been reported yet. Here, we present an extended UPS-NF of the breast including its comprehensive molecular workup.

METHODS

A 58-year-old female presented with general malaise, fever spikes, weight loss, and a massively swollen left breast. C-reactive protein and blood leucocytes were significantly increased. However, repeated blood cultures and smears were all sterile. Histopathology of the abscess-forming tumor revealed an undifferentiated malignancy with numerous of tumor giant cells as well as spindle-shaped cells with nuclear pleomorphism and hyperchromasia. Immunohistochemistry demonstrated partial, patchy desmin staining and weak heterogonous neuron-specific enolase immunoreactivity of tumor cells, but a focal staining for Melan-A.

RESULTS

Neither common melanoma driver mutations nor an ultraviolet mutational signature was detected by whole genome sequencing. Using FISH and RT-PCR we also excluded translocations characteristic for clear cell sarcoma. Thus, the diagnosis of inflammatory UPS-NF of the breast was considered highly probable. Despite a complete mastectomy, the tumor recurred after only three months. This recurrence was treated with a combination of ipilimumab and nivolumab based on the primary tumor's TPS score for PD-L1 of 30%. After an initial response, however, the tumor was progressive again.

CONCLUSION

We describe here the first case of UPS-NF of the breast, which shows great clinical and histopathologic resemblances to previously reported UPS-NF of other anatomic localizations.

Mesenchymal tumours with melanocytic expression: a potential pitfall in the differential diagnosis of malignant melanoma

Mesenchymal tumours with melanocytic expression can pose a diagnostic challenge because they frequently demonstrate both morphological and immunohistochemical overlap with other cutaneous melanocytic neoplasms. Therefore, they present potential pathological pitfalls that may lead to a misdiagnosis of malignant melanoma. Mesenchymal neoplasms that closely mimic melanoma include malignant melanotic nerve sheath tumour (melanotic schwannoma), epithelioid schwannoma, malignant peripheral nerve sheath, cutaneous syncytial myoepithelioma, clear cell sarcoma of soft tissue, and perivascular epithelioid cell tumour. Awareness of these melanoma mimics is necessary for establishing the correct diagnosis so that the appropriate clinical management can be rendered to the patient. This in-depth review highlights key diagnostic features and molecular genetics and also discusses the differential diagnosis and treatment of mesenchymal tumours that exhibit melanocytic expression.

Targeting epigenetic features in clear cell sarcomas based on patient-derived cell lines

BACKGROUND

Clear cell sarcomas (CCSs) are translocated aggressive malignancies, most commonly affecting young adults with a high incidence of metastases and a poor prognosis. Research into the disease is more feasible when adequate models are available. By establishing CCS cell lines from a primary and metastatic lesion and isolating healthy fibroblasts from the same patient, the in vivo process is accurately reflected and aspects of clinical multistep carcinogenesis recapitulated.

METHODS

Isolated tumor cells and normal healthy skin fibroblasts from the same patient were compared in terms of growth behavior and morphological characteristics using light and electron microscopy. Tumorigenicity potential was determined by soft agar colony formation assay and in vivo xenograft applications. While genetic differences between the two lineages were examined by copy number alternation profiles, nuclear magnetic resonance spectroscopy determined arginine methylation as epigenetic features. Potential anti-tumor effects of a protein arginine N-methyltransferase type I (PRMT1) inhibitor were elicited in 2D and 3D cell culture experiments using cell viability and apoptosis assays. Statistical significance was calculated by one-way ANOVA and unpaired t-test.

RESULTS

The two established CCS cell lines named MUG Lucifer prim and MUG Lucifer met showed differences in morphology, genetic and epigenetic data, reflecting the respective original tissue. The detailed cell line characterization especially in regards to the epigenetic domain allows investigation of new innovative therapies. Based on the epigenetic data, a PRMT1 inhibitor was used to demonstrate the targeted antitumor effect; normal tissue cells isolated and immortalized from the same patient were not affected with the IC50 used.

CONCLUSIONS

MUG Lucifer prim, MUG Lucifer met and isolated and immortalized fibroblasts from the same patient represent an ideal in vitro model to explore the biology of CCS. Based on this cell culture model, novel therapies could be tested in the form of PRMT1 inhibitors, which drive tumor cells into apoptosis, but show no effect on fibroblasts, further supporting their potential as promising treatment options in the combat against CCS. The data substantiate the importance of tailored therapies in the advanced metastatic stage of CCS.

A Clear Cell Sarcoma Case: A Diagnostic and Treatment Challenge, with a Promising Response to Trabectedin

INTRODUCTION

Clear cell sarcoma (CCS) is a rare and aggressive soft tissue sarcoma. CCS is characterized by the translocation t(12;22) (q13;q12), involving the fusion of EWSR1 and ATF1 genes, and less frequently the fusion gene EWSR1-CREB1. Usually, CCSs are considered poorly responsive to conventional chemotherapy. However, trabectedin has shown activity against translocation-related sarcomas. Furthermore, preclinical results suggest that trabectedin is a promising antitumor agent for CCS, potentially inducing melanocytic differentiation.

CASE PRESENTATION

We report the case of a challenging anatomopathological diagnosis in a patient with an aggressive metastatic CCS. Following the diagnosis of CCS, the patient experienced a clinical and radiological tumor response to trabectedin after four lines of treatment.

CONCLUSION

This is a novel report of CCS treated with trabectedin that resulted in a partial response and suggests the need for further research on trabectedin as a therapeutic option for CCS.

Clear cell sarcoma of soft tissue with plasmacytoid morphology: A rare case report

RATIONALE

Clear cell sarcoma of soft tissue (CCSST) is a rare malignant tumor that occurs in the extremities of young adults. CCSST has been documented to have atypical histopathological features, such as epidermotropism or myxoid differentiation, which may set pitfalls in the differential diagnosis. We report a case of CCSST with plasmacytoid morphology which has never been described.

PATIENT CONCERNS

A 15-year-old male, presented with a 5-cm mass in his left inguinal area.

DIAGNOSIS

Positron emission tomography-computed tomography examination showed nodules in the left groin and the lung, the latter was considered metastasis. A core needle biopsy with the diagnosis of CCSST with plasmacytoid morphology was made according to histology, immunostaining, and molecular analysis.

INTERVENTIONS

The patient received chemotherapy of doxorubicin and ifosfamide.

OUTCOMES

The patient failed to respond to the standard chemotherapy and deceased twelve months after diagnosis.

LESSONS

This special case of CCSST with plasmacytoid features demonstrated a morphological variation never been documented and may easily lead to misdiagnosis. For such cases, molecular analysis is essential to provide solid evidence for accurate diagnosis.

Primary clear cell sarcoma of soft tissue in the posterior cervical spine invading the medulla oblongata: A case report

BACKGROUND

Clear cell sarcoma (CCS) is a rare and highly malignant soft tissue tumor, usually occurring in the deep soft tissues of the distal tendons and aponeurosis of the extremities, especially the feet and knees. CCS originating in the head and neck is extremely rare. The clinical manifestations of CCS in the head and neck are not typical, and the imaging manifestations have certain characteristics, but the diagnosis still depends on pathological examination and genetic testing.

CASE SUMMARY

A 33-year-old male patient had paroxysmal headache for more than 4 years, accompanied by nausea and vomiting, which could be relieved after rest. Computed tomography angiography showed a left paraspinal soft tissue mass. Contrast-enhanced imaging showed obvious uneven enhancement with adjacent bone lytic destruction. Magnetic resonance imaging examination showed isosignal on T₁-weighted images, slightly high signal on T₂-weighted images (T₂WI), high signal on Tirm fat suppression sequence, significantly high signal on diffusion weighted imaging, and obvious and uneven enhancement. The lesion invaded the anterior medulla oblongata through the left atlantoaxial foramen and compressed the cervical spinal cord on T₂WI. Primary CCS of soft tissue was diagnosed by pathology and genetic examination.

CONCLUSION

CCS should be considered in the differential diagnosis of soft tissue tumors of the head and neck, and their diagnosis depends on pathological examination and genetic testing.

Malignant Superficial Mesenchymal Tumors in Children

Malignant superficial mesenchymal tumors are a very diverse group of neoplasms with few clinical and radiological discriminatory factors. Hence, some of these cancers are rarely suspected based on clinical and radiological grounds, others may be easily misdiagnosed, and the histological analysis of a biopsy or resection is central in the diagnostic process. In children, the age at presentation is a major element of the differential diagnosis. Some tumors have a very distinct epidemiology, while others may be seen at any age. More recently, the advances in molecular biology have greatly improved the diagnosis of mesenchymal tumors and new entities are still being described. In the present review, we provide an overview of the diversity of malignant superficial mesenchymal tumors in children, including new and/or rare entities. We discuss the important diagnostic features, be they clinical, histological, or molecular. Special attention was given to the genetic features of these tumors, particularly when they were helpful for the diagnosis or treatment.

Clinical Experience with Apatinib and Camrelizumab in Advance Clear Cell Sarcoma: A Retrospective Study

Purpose

Advanced clear cell sarcoma (CCS) is a rare subtype of sarcoma with few effective treatments. Evidence shows that apatinib is efficacious and safe for CCS. This study aimed to assess the safety and efficacy of apatinib and/or camrelizumab (a PD-1 inhibitor) in treating advanced CCS.

Methods

We retrospectively reviewed 12 patients with advanced CCS who received apatinib and/or camrelizumab therapy between November 2018 and July 2021. Standard descriptive statistics were employed for continuous variables and categorical variables (number and percentage).

Results

Of the 12 CCS patients, 3 had a partial response (PR), and 4 had stable disease (SD). Among the 5 patients treated with apatinib monotherapy, 1 PR and 2 SD were found, and the addition or replacement of camrelizumab after progressive disease (PD) did not work. In the 4 patients who received apatinib plus camrelizumab combination therapy, 1 PR and 1 SD were found. All 3 patients who received camrelizumab first had PD, and 1 PR and 1 SD were found after adding apatinib. Grade 3 or 4 adverse events were significantly more common in the apatinib plus camrelizumab combination therapy than in the apatinib or camrelizumab monotherapy, and these included increased aspartate aminotransferase and increased alanine aminotransferase levels.

Conclusion

Apatinib has promising effectiveness for CCS. Camrelizumab efficacy for the treatment of clear cell sarcoma is inconclusive. The efficacy of apatinib and PD-1 inhibitors in CCS need to be further investigated in prospective clinical trials.

Molecular targeted therapy for advanced or metastatic soft tissue sarcoma

Soft tissue sarcomas are a form of rare and heterogeneous neoplasms with high recurrence rate and mortality. Over the past decades, less progress has been achieved. Surgical management with or without adjuvant/neoadjuvant radiotherapy is still the first-line treatment for localized soft tissue sarcomas, and chemotherapy is the additional option for those with high-risk. However, not all patients with advanced or metastatic soft tissue sarcomas benefit from conventional chemotherapy, targeted therapy takes the most relevant role in the management of those resistant to or failed to conventional chemotherapy. Heterogeneous soft tissue sarcomas vary from biological behavior, genetic mutations, and clinical presentation with a low incidence, indicating the future direction of histotype-based even molecule-based personalized therapy. Furthermore, increasing preclinical studies were carried out to investigate the pathogenesis and potential therapeutic targets of soft tissue sarcomas and increasing new drugs have been developed in recent years, which had started opening new doors for clinical treatment for patients with advanced/metastatic soft tissue sarcomas. Here we sought to summarize the concise characteristics and advance in the targeted therapy for the most common subtypes of soft tissue sarcomas.

Uncommon and peculiar soft tissue sarcomas: Multidisciplinary review and practical recommendations. Spanish Group for Sarcoma research (GEIS -GROUP). Part II

Among all Soft Tissue sarcomas there are some subtypes with low incidence and/or peculiar clinical behaviour, that need to be consider separately. Most of them are orphan diseases, whose biological characteristics imply a clearly different diagnostic and therapeutic approach from other more common sarcoma tumors. We present a brief and updated multidiciplinary review, focused on practical issues, aimed at helping clinicians in decision making. In this second part we review these subtypes: Alveolar Soft Part Sarcoma, Epithelioid Sarcoma, Clear Cell Sarcoma, Desmoplastic Small Round Cell Tumor, Rhabdoid Tumor, Phyllodes Tumor, Tenosynovial Giant Cell Tumors, Myoepithelial Tumor, Perivascular Epithelioid Cell Neoplasms (PEComas), Extraskeletal Myxoid Chondrosarcoma, NTRK-fusions Sarcomas. Most of them present their own radiological and histopathological feautures, that are essential to know in order to achieve early diagnosis. In some of them, molecular diagnosis is mandatory, not only in the diagnosis, but also to plan the treatment. On the other hand, and despite the low incidence, a great scientific research effort has been made to achieve new treatment opportunities for these patients even with approved indications. These include new treatments with targeted therapies and immunotherapy, which today represent possible therapeutic options. It is especially important to be attentive to new and potential avenues of research, and to promote the conduct of specific clinical trials for rare sarcomas.

An obstructive role of NK cells on metastatic growth of clear-cell sarcoma cells in a xenoplant murine model

Clear cell sarcoma (CCS) affects the deep soft tissues in young adults and is known to have high rates of metastasis, including lymphatic metastasis. In our previous study an xenoplant model of CCS was established, which exhibited local tumor growth, lymphatic metastasis, and distant metastasis in SCID-Beige mice. In the current study, the role of NK cells during metastasis in the same xenoplant murine model was investigated. Injection of murine or human NK cells significantly suppressed the metastasis of HS-MM CCS cells in SCID-Beige mice. Notably, reverse transcription-quantitative PCR analysis demonstrated that injection of NK cells did not alter the mRNA expression levels of ERSR1-ATF1, which is specifically transcribed in CCS, in the buffy coat of circulating blood cells of HS-MM-xenoplanted SCID-Beige mice. BALB/c nude mice xenoplanted with HS-MM cells exhibited local growth without evident metastasis, whereas inoculation with the anti-asialo-GM1 antibody, which has previously been found to abolish NK-cell activity, resulted in metastasis of HS-MM cells in BALB/c nude mice. The injection of the anti-CD96 antibody, which increases the cytotoxicity of NK cells, significantly suppressed the metastasis of HS-MM cells in SCID-Beige mice. These results indicated that NK cells impaired the metastatic tumor microenvironments in the present mice xenoplant model.

Boron neutron capture therapy for clear cell sarcoma

Clear cell sarcoma of tendons and aponeuroses (CCS) is a rare, malignant tumor arising in lower extremities with no effective treatment other than wide surgical resection. Here described is a case of primary CCS in the peroneal tendon of the right foot of a 54-year-old woman enrolled to undergo BNCT. The tumor mass post-BNCT disappeared totally without damage to other normal tissue, demonstrating, for the first time, the potential efficacy of BNCT in complete local control of CCS.

Rare Tumor-Normal Matched Whole Exome Sequencing Identifies Novel Genomic Pathogenic Germline and Somatic Aberrations

Whole exome sequencing (WES) of matched tumor-normal pairs in rare tumors has the potential to identify genome-wide mutations and copy number alterations (CNAs). We evaluated 27 rare cancer patients with tumor-normal matching by WES and tumor-only next generation sequencing (NGS) as a comparator. Our goal was to: 1) identify known and novel variants and CNAs in rare cancers with comparison to common cancers; 2) examine differences between germline and somatic variants and how that functionally impacts rare tumors; 3) detect and characterize alleles in biologically relevant genes-pathways that may be of clinical importance but not represented in classical cancer genes. We identified 3343 germline single nucleotide variants (SNVs) and small indel variants-1670 in oncogenes and 1673 in tumor suppressor genes-generating an average of 124 germline variants/case. The number of somatic SNVs and small indels detected in all cases was 523:306 in oncogenes and 217 in tumor suppressor genes. Of the germline variants, six were identified to be pathogenic or likely pathogenic. In the 27 analyzed rare cancer cases, CNAs are variable depending on tumor type, germline pathogenic variants are more common. Cell fate pathway mutations (e.g., Hippo, Notch, Wnt) dominate pathogenesis and double hit (mutation + CNV) represent ~18% cases.

Spindle Cell Sarcoma of the Maxilla: A Rare Entity, Case Report, and Review of the Literature

Spindle cell sarcoma (SCS) is a malignancy, with the most recent Surveillance, Epidemiology, and End Results (SEER) data citing a total of 250 reported cases occurring in the head and neck. Of these cases, none originated in the maxillofacial hard tissue. To the best of our knowledge, only 2 cases of primary osseous SCS of the maxillofacial region have been reported. These cases were not accounted for in the SEER data. The diagnosis of SCS requires its differentiation from other sarcomas and spindle cell neoplasms. Therefore, a comprehensive review to reinforce its inclusion in oral and maxillofacial surgeons' differential diagnosis for osseous neoplastic pathology is desired. In the present case report, we have described a maxillary SCS in a patient with an initial diagnosis of a spindle cell lesion of uncertain biologic behavior. We reviewed the data for SCS, including the epidemiologic data, diagnostic challenges, clinical and radiographic presentations, prognostic indicators, and treatment.

Clear cell sarcoma of soft tissue in pleural cavity: A case report

BACKGROUND

Clear cell sarcoma (CCS) of soft tissue is a rare malignant soft tissue sarcoma usually reported to locate at distal end of extremities and rarely at trunk. Herein, we report a case of CCS in pleural cavity.

CASE SUMMARY

A 31-year-old male was admitted for an uncertain mass in left pleural cavity in routine physical examination without any symptoms. A VATS surgery was performed to remove the tumor. The pathological finding displayed a cystic mass with 6.5 cm at the longest diameter, dark red in section and cysts could be found locally. A strong expression of S-100, HMB45 and Vimentin was detected in immunohistochemical staining, which was inclined to the diagnosis of the CCS of soft tissue. The patient refused chemotherapy, radiotherapy and targeted therapy because of the personal financial situation. Follow-up computed tomography scans were done at the 90^th postoperative day and the 180^th postoperative day, and no obvious sign of recurrence was found till now.

CONCLUSION

CCS of soft tissue also can be found in pleural cavity although in an extremely rare incidence. Radical resection is useful to improve the prognosis.