Sarcoma is comprised of a heterogeneous group of tumors originating from the mesenchyme. Sarcoma is also the first tumor that responded to immunotherapeutic agents often termed as “Coley's toxins.” However, immunotherapy is yet to establish its presence in sarcomas. Complex interactions between tumor and immune cells in the tumor microenvironment play a crucial role in response to immunotherapy. There is a dynamic equilibrium created by the immune cells infiltrating the tumor, and this forms the basis of tumor evasion. Manipulating the intratumoral microenvironment will help overcome tumor evasion.

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Purpose. Patients with large >5 cm, high-grade resectable soft tissue sarcomas (STS) have the highest risk of distant metastases. Previously we have shown that dendritic cell (DC) based vaccines show consistent immune responses. Methods. This was a Phase I single institution study of neoadjuvant radiation with DC injections on 18 newly diagnosed high-risk STS patients. Neoadjuvant treatment consisted of 50 Gy of external beam radiation (EBRT), given in 25 fractions delivered five days/week, combined with four intratumoral injections of DCs followed by complete resection. The primary endpoint was to establish the immunological response to neoadjuvant therapy and obtain data on its clinical safety and outcomes. Results. There were no unexpected toxicities or serious adverse events. Twelve out of 18 (67%) patients were alive, of which an encouraging 11/18 (61%) were alive with no systemic recurrence over a period of 2–8 years. Favorable immunological responses correlated with clinical responses in some cases. Conclusions. This study provides clinical support to using dendritic cell injections along with radiation in sarcomas, which when used optimally in combination can help clinical outcomes in soft tissue sarcoma. Study registration number is NCT00365872.

e22548 Background: Clinical responses in patients with soft tissue sarcoma administered immune checkpoint inhibitors have been infrequent. Little is known regarding the immune microenvironment in soft tissue sarcoma that leads to a lack of effective responses with immune therapies. Whilst several studies have shown T cell infiltration in sarcomas, these tumors do not respond to immunotherapies. Macrophages are important regulators of immune responses in the tumor microenvironment. Studies in mouse models indicate that macrophages regulate immune checkpoint inhibitor response. With the overall goal of developing more effective combination immunotherapies for sarcoma, we examined tumor associated macrophages in patients with soft tissue sarcoma administered neoadjuvant chemotherapy. Interactions between macrophage infiltration, tumor immunogenicity and overall survival were also assessed using publicly available RNAseq and exome mutation data. Methods: Immunohistochemistry was performed on formalin fixed soft tissue sarcoma tissue. Tissues from 20 patients with soft tissue sarcoma pre and post neo-adjuvant chemotherapy were included. TAMs were detected by CD68; M2 subtype were detected by CD163. CD4, CD8, and CD25 T cells were also examined. The density of CD68+ TAMs, CD163+ TAMs and the ratio of CD163+ TAMs / CD68+ TAMs were calculated and their correlation with survival was also made. Publicly available RNAseq and exome mutation data were assembled from The Cancer Genome Atlas (TCGA) sarcoma cohort (n = 259). For each tumor, a relative measure of abundance of tumor-infiltrating macrophages was estimated using gene expression. Tumor mutational burden (TMB), expressed as the rate of non- synonymous mutations per megabase of sequenced DNA, was used as a measure of tumor immunogenicity. Interactions between macrophage infiltration, tumor immunogenicity and overall survival were assessed by Cox regression and Kaplan-Meier analysis. Categorical relationships involving clinical, immunologic, and genomic features of the tumor immune subclasses were compared. Results: Specific alteration in the density of CD68+ TAMs, CD163+ TAMs, and the CD163 / CD68 ratio were observed in patients with soft tissue sarcoma responding to neoadjuvant chemotherapy. Categorical relationships involving macrophage infiltration, TMB, and survival were also observed. Conclusions: These study support the targeting of tumor associated macrophages in patients with soft tissue sarcoma and suggest that changes in TAMs may be achievable using neoadjuvant chemotherapy.

Endometriosis is a common gynecological disorder most often involving the pelvic region. Although it is rare, endometriosis occurring outside of the peritoneal cavity most commonly occurs within scars of the abdominal wall, but it has been reported in the lungs, pleura, kidneys, brain, and the extremities. Herein, we present 2 cases of endometriosis, including 1 case of endometriosis of the wrist that clinically mimicked a soft-tissue neoplasm and 1 case of right-groin endometriosis mimicking synovial sarcoma during the initial pathological interpretation of findings on fine needle aspiration. We also report on a third patient with synovial sarcoma to demonstrate a diagnostic pitfall. To our knowledge, endometriosis within the skeletal muscle of the wrist has not been previously reported in the literature. A literature review was performed, and we discuss how this diagnostic pitfall may be avoided. We review the techniques for diagnosing synovial sarcoma and the importance of a high index of suspicion for endometriosis when investigating any soft-tissue mass in a female patient of reproductive age. Adequate pathological evaluation in conjunction with the correlating clinical and radiological information should help facilitate an accurate diagnosis.