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Undifferentiated pleomorphic sarcoma (UPS) and malignant peripheral nerve sheath tumor (MPNST) are aggressive soft tissue sarcomas that do not respond well to current treatment modalities. The limited availability of UPS and MPNST cell lines makes it challenging to identify potential therapeutic targets in a laboratory setting. Understanding the urgent need for improved treatments for these tumors and the limited cellular models available, we generated additional cell lines to study these rare cancers. Patient-derived tumors were used to establish 4 new UPS models, including one radiation-associated UPS-UPS271.1, UPS511, UPS0103, and RIS620, one unclassified spindle cell sarcoma-USC060.1, and 3 new models of MPNST-MPNST007, MPNST3813E, and MPNST4970. This study examined the utility of the new cell lines as sarcoma models by assessing their tumorigenic potential and mutation status for known sarcoma-related genes. All the cell lines formed colonies and migrated in vitro. The in vivo tumorigenic potential of the cell lines and corresponding xenografts was determined by subcutaneous injection or xenograft re-passaging into immunocompromised mice. USC060.1 and UPS511 cells formed tumors in mice upon subcutaneous injection. UPS0103 and RIS620 tumor implants formed tumors in vivo, as did MPNST007 and MPNST3813E tumor implants. Targeted sequencing analysis of a panel of genes frequently mutated in sarcomas identified TP53, RB1, and ATRX mutations in a subset of the cell lines. These new cellular models provide the scientific community with powerful tools for detailed studies of tumorigenesis and for investigating novel therapies for UPS and MPNST., (© 2022. The Author(s), under exclusive licence to United States and Canadian Academy of Pathology.)

New York esophageal squamous cell carcinoma 1 (NY-ESO-1, CTAG1B) is a cancer-testis antigen and currently a focus of several targeted immunotherapeutic strategies. We performed a large-scale immunohistochemical expression study of NY-ESO-1 using tissue microarrays of mesenchymal tumors from three institutions in an international collaboration. A total of 1132 intermediate and malignant and 175 benign mesenchymal lesions were enrolled in this study. Immunohistochemical staining was performed on tissue microarrays using a monoclonal antibody for NY-ESO-1. Among mesenchymal tumors, myxoid liposarcomas showed the highest positivity for NY-ESO-1 (88%), followed by synovial sarcomas (49%), myxofibrosarcomas (35%), and conventional chondrosarcomas (28%). Positivity of NY-ESO-1 in the remaining mesenchymal tumors was consistently low, and no immunoreactivity was observed in benign mesenchymal lesions. On the basis of these findings, nearly 90% of myxoid liposarcomas, as well as a significant proportion of synovial sarcomas, myxofibrosarcomas, and conventional chondrosarcomas are good candidates for immunotherapy targeting NY-ESO-1.

Metastasis causes most cancer deaths, but is incompletely understood. MicroRNAs can regulate metastasis, but it is not known whether a single miRNA can regulate metastasis in primary cancer models in vivo. We compared the expression of miRNAs in metastatic and nonmetastatic primary mouse sarcomas and found that microRNA-182 (miR-182) was markedly overexpressed in some tumors that metastasized to the lungs. By utilizing genetically engineered mice with either deletion of or overexpression of miR-182 in primary sarcomas, we discovered that deletion of miR-182 substantially decreased, while overexpression of miR-182 considerably increased, the rate of lung metastasis after amputation of the tumor-bearing limb. Additionally, deletion of miR-182 decreased circulating tumor cells (CTCs), while overexpression of miR-182 increased CTCs, suggesting that miR-182 regulates intravasation of cancer cells into the circulation. We identified 4 miR-182 targets that inhibit either the migration of tumor cells or the degradation of the extracellular matrix. Notably, restoration of any of these targets in isolation did not alter the metastatic potential of sarcoma cells injected orthotopically, but the simultaneous restoration of all 4 targets together substantially decreased the number of metastases. These results demonstrate that a single miRNA can regulate metastasis of primary tumors in vivo by coordinated regulation of multiple genes.

We report on an optical noncontact method for the detection of soft-tissue tumors based on the measurement of their elasticity. A focused air-puff system is used to excite surface waves (SWs) on soft tissues with transient static pressure. A high-speed phase-sensitive optical coherence tomography system is used to measure the SWs as they propagate from the point of excitation. To evaluate the stiffness of soft tissues, the Young's modulus is quantified based on the group velocity of SWs. Pilot experiments were performed on ex vivo human myxoma and normal fat. Results demonstrate the feasibility of the proposed method to measure elasticity and differentiate soft-tissue tumors from normal tissues.

Soft tissue sarcomas are an uncommon and diverse group of more than 50 mesenchymal malignancies. The pathogenesis of many of these is poorly understood, but others have begun to reveal the secrets of their underlying mechanisms. With considerable effort over recent years, soft tissue sarcomas have increasingly been classified on the basis of underlying molecular alterations. In turn, this has allowed the development and application of targeted agents in several specific, molecularly defined, sarcoma subtypes. This review will focus on the rationale for targeted therapy in sarcoma, with emphasis on the relevance of specific molecular factors and pathways in both translocation-associated sarcomas and in genetically complex tumors. In addition, we will address some of the early successes in sarcoma-targeted therapy as well as a few challenges and disappointments in this field. Finally, we will discuss several possible opportunities represented by poorly understood, but potentially promising new therapeutic targets, as well as several novel biological agents currently in preclinical and early phase I/II trials. This will provide the reader with the context for understanding the current state of this field and a sense of where it may be headed in the coming years.

Unlike melanoma, clear cell sarcoma harbors either a t(12;22)(q13;q12) recurrent translocation, resulting in an EWSR1/ATF1 chimeric gene, or less commonly a t(2;22)(q34;q12) translocation fusing EWSR1 and CREB1. Few studies have examined the prevalence of all chimeric types and variants to assess the usage of ancillary genetic testing in routine diagnosis. We investigated rearrangement prevalence in 17 clear cell sarcomas, two positive control cell lines, and two melanomas (negative controls). Fluorescence in situ hybridization (FISH) analysis using the LSI EWSR1 break-apart probe and a reverse transcription polymerase chain reaction (RT-PCR) assay optimized for formalin-fixed paraffin-embedded tissue to detect all four reported EWSR1/ATF1 clear cell sarcoma chimeric types and the EWSR1/CREB1 variant was performed. All 15 cases available for testing by FISH were positive for EWSR1 rearrangement including two cases with insufficient RNA for RT-PCR. Thirteen of 15 cases successfully tested by RT-PCR harbored a type 1 chimeric transcript (EWSR1 exon 8/ATF1 exon 4), of which five tumors simultaneously carried a type 2 chimeric transcript (EWSR1 exon 7/ATF1 exon 5). One case carried a type 2 transcript alone and one case contained an EWSR1/CREB1 transcript. Both control cases were positive by both techniques with one case carrying both types 1 and 2 chimeric transcripts and the other types 2 and 3 (EWSR1 exon 10/ATF1 exon 5). Consequently, both techniques are equally effective in assessing for an EWSR1 rearrangement and are useful ancillary diagnostic tests for clear cell sarcoma. They also reinforce the prevalence of this translocation in these tumors. In addition, EWSR1-CREB1 was identified in a clear cell sarcoma of soft tissue providing further evidence that this chimeric variant is not exclusive to gastrointestinal clear cell sarcomas and should be included in RT-PCR assays of soft tissue clear cell sarcomas.

Gastrointestinal stromal tumors (GISTs) rarely metastasize to the skin. We describe 5 patients with GIST with subcutaneous and cutaneous metastases. The mean age at metastasis was 54 years (range 30-68 years) with a male predominance (4:1). Primary tumors occurred in the stomach (n = 3), small bowel (n = 1), and abdomen, not otherwise specified (n = 1). The average time from primary tumor resection to the resection of skin metastases was 59 months (range 11-155 months). The metastases occurred in the scalp (n = 2), cheek (n = 1), and abdomen (n = 2) with 3 patients presenting with solitary nodules and 2 patients with multiple nodules. The average size was 2 cm (range 0.6-4 cm). Histologically, 2 cases were spindled and 3 cases demonstrated mixed epithelioid and spindle cell morphology. All were confirmed to have CD117 reactivity. KIT genotyping was performed in 4 of 5 cases. Two cases harbored a mutation in exon 11, and the remaining 2 cases were wild type in exons 9, 11, 13, and 17. All 5 patients had multiple concurrent or subsequent abdominal and/or hepatic metastases. In 4 patients with an average follow-up of 32 months (range 6-75 months), after the resection of the metastases, 2 were alive with disease and 2 died of disease. Cutaneous metastases seem to be a late complication of GIST, but their presence does not necessarily herald a rapid demise of the patient.

Extraskeletal myxoid chondrosarcoma is a rare soft tissue tumor characterized by a nodular growth pattern with eosinophilic cells usually in a reticular pattern and abundant myxoid stroma. In contrast to other myxoid sarcomas, the majority of extraskeletal myxoid chondrosarcomas harbor a balanced translocation, t(9;22)(q22;q12), that fuses EWSR1 with NR4A3 (also known as CHN). Other less common translocations involving NR4A3 have also been described. We examined the diagnostic utility of fluorescence in situ hybridization for extraskeletal myxoid chondrosarcoma using the LSI EWSR1 break-apart probe (Abbott Molecular/Vysis, Des Plaines, IL, USA). Sixteen cases of extraskeletal myxoid chondrosarcoma with formalin-fixed paraffin-embedded tissue available were retrieved (1991-2007). The mean age at time of presentation was 57 years (range, 30-78). The male to female ratio was 7:1. All cases where either consistent with or highly suggestive of the diagnosis, with most of the primary tumors occurring in the thigh, inguinal or gluteal region. Fifteen of 16 cases were analyzable, of which 14 (93%) were positive for the rearrangement of the EWSR1 locus. In this study, the vast majority of extraskeletal myxoid chondrosarcomas are associated with a rearrangement at the EWSR1 locus (22q12). Fluorescence in situ hybridization is useful to support the diagnosis of extraskeletal myxoid chondrosarcomas and may help to differentiate it from mimics such as other myxoid sarcomas, particularly in limited biopsies.

Human sarcomas are rare but diverse malignant tumors derived from mesenchymal tissue. Clinical response to therapy is currently determined by the modified World Health Organization (WHO) criteria or the Response Evaluation Criteria in Solid Tumors (RECIST), but these standards correlate poorly with sarcoma patient outcome. We introduced ligand-directed particles with elements of AAV and phage (AAVP) to enable integration of tumor targeting to molecular imaging. We report drug-response monitoring and prediction in a nude rat model of human sarcoma by AAVP imaging. As a proof-of-concept, we imaged Herpes simplex thymidine kinase in a clinic-ready setting with PET to show that one can a priori predict tumor response to a systemic cytotoxic. Given the target expression in patient-derived sarcomas, this platform may be translated in clinical applications. Sarcoma-specific ligands and promoters may ultimately lead to an imaging transcriptome.