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Background Desmoid-Type Fibromatosis (DTF) is a rare mesenchymal neoplasm with a locally invasive pattern and high risk of local recurrence after surgery. Historically, the standard treatment for DTF was surgical resection. However, considering the difficulty of achieving surgical eradication, the possible unnecessary morbidity and the unpredictability of the natural history, a wait-and-see approach has been proposed for asymptomatic DTF. Methods We analyzed 87 consecutive patients with histologically-proven sporadic primary DTF, first recurrence or residual disease managed at our institution between 2000 and 2018. Patients and tumor-related variables were reviewed and analyzed. Two different treatment strategies were adopted according to different time periods: in the “early period” (2000–2010) patients underwent surgical treatment irrespective of the clinical presentation, whereas in the “late period” (2012–2018) asymptomatic patients used to undergo a wait-and-see strategy. The event-free survival (EFS) was compared trough a pre-post comparison. Results In the early period, surgery was performed in 51 (94.4%) patients and watchful waiting in 3 (5.6%). In the late period, the watchful waiting group accounted for 24 (72.7%) patients and the surgical group for 9 (27.3%). No statistically independent prognostic factors were found. EFS did not show statistically significant differences between early and late period groups. Conclusion Wait-and-see policy has shown to be equivalent to upfront surgery in terms of EFS; therefore, a conservative approach is recommended in asymptomatic patients diagnosed with DTF that can be followed through watchful waiting.

Myoid gonadal stromal tumor represents a rare testicular neoplasm displaying smooth muscular and gonadal stromal differentiation. This entity has very few cases reported in the literature that describe heterogeneous clinical and pathological characteristics. Bayesian statistics provides a useful framework to combine information from diverse sources. We here presented a case series-the largest so far reported-of myoid gonadal stromal tumor (4 cases) with extensive morphologic, immunohistochemical, and molecular characterization, performed a systematic review of the literature (that identified 9 papers), and used a Bayesian data analysis to understand the characteristics of this disease. Our study collectively described 16 cases. This neoplasm is mainly found in adults (mean age about 40 years) and often has a size of about 3 cm. By morphology, the tumor can infiltrate testicular tubules and is composed of spindle cells; few mitoses can be seen (usually 2/10 HPF). Neoplastic cells are diffusely positive with α-smooth muscle actin with a tram-track staining pattern. S100 protein, FOXL2, and SF1 are also characteristically positive. Moreover, this neoplasm can display epithelial differentiation, in about half of the cases. In conclusion, we foresee the use of this statistical approach in pathology: our analysis allowed a more precise description of this rare entity.

MRP-1 is implicated in multidrug resistance and was described as prognostic in high-risk patients with soft-tissue sarcoma (STS) in a previous study. The current research aimed to validate MRP-1 prognostic/predictive value in localized sarcomas treated with anthracyclines plus ifosfamide within the ISG-1001 phase III study. In addition, the inhibitory activity on MRP-1 was investigated in preclinical studies to identify new combinations able to increase the efficacy of standard chemotherapy in STS. MRP-1 expression was assessed by IHC in tissue microarrays from patients with STS and tested for correlation with disease-free survival (DFS) and overall survival (OS). In vitro studies tested the efficacy of MRP-1 inhibitors (nilotinib, ripretinib, selumetinib, and avapritinib) in sarcoma cell lines. The effect of combinations of the most active MRP-1 inhibitors and chemotherapy was measured on the basis of apoptosis. MRP-1 was evaluable in 231 of 264 cases who entered the study. MRP-1 expression (strong intensity) was independently associated with worse DFS [HR, 1.78; 95% confidence interval (CI), 1.11–2.83; P = 0.016], in the multivariate analysis, with a trend for a worse OS (HR, 1.78; 95% CI, 0.97–3.25; P = 0.062). In vitro studies showed that the addition of MRP-1 inhibitors (nilotinib or avapritinib) to doxorubicin plus palifosfamide, significantly increased cell death in SK-UT-1 and CP0024 cell lines. MRP-1 is an adverse predictive factor in localized high-risk patients with STS treated with neoadjuvant anthracyclines plus ifosfamide followed by surgery. In vitro findings support the clinical assessment of the combination of chemotherapy and MRP-1 inhibitors as a promising strategy to overcome the drug ceiling effect for chemotherapy., The study was partially funded through a European Union grant (EUROSARC FP7 278472). The authors would like to thank Patricio Ledesma Figueroa for Data Management. J. Martin-Broto, D.S. Moura and N. Hindi would like to thank the International Accelerator Award funded by Cancer Research UK [C56167/A29363], Associazione Italiana per la Ricerca sul Cancro [AIRC - 24297] and Fundacion Científica – Asociacion Espanola Contra el Cancer [Foundation AECC - GEACC19007MA]. D.S. Moura was supported by a Sara Borrell grant (CD20/00155) funded by the Instituto de Salud Carlos III. C. Romagosa was supported by a grant from the “Programa d'impuls del talent i de l'ocupabilitat del PERIS 2016–2020.” J-Y. Blay would like to express gratitude for the support from NetSARC (INCA and DGOS) EURACAN (EC 739521) and LYRICAN (INCA-DGOS-INSERM 12563). The ISH1001 study was supported by Eurosarc (FP7–278742).

Background: Paravertebral localization of primary undifferentiated pleomorphic sarcoma (UPS) with bone and vascular involvement is infrequent and challenging. Multi-step surgical procedure has been described as a feasible and effective option to achieve sustained local tumor control.Methods: We report on a 62-year old man with paravertebral UPS infiltrating the aortic wall and the 9th thoracic vertebra who underwent a multi-step surgical procedure aimed at achieving oncologic radicality through a coordinated effort between thoracic, vascular and spinal surgeons. After balancing the risks and benefits of perioperative therapies, upfront surgery was performed including aortic resection with bypass grafting followed by a triple en bloc vertebrectomy with tumor excision. Mid-term follow-up (22 months) is then provided.Results: The combined procedure achieved oncological radicality and no local recurrence in the mid-term. No major complications occurred.Conclusions: Multi-step and multi-specialty surgery is a feasible and effective strategy to treat primary UPS in unfavorable localization. A strategic cooperation between surgeons and a multidisciplinary tumor board is required to define an optimal, personalized treatment strategy in sarcoma patients.

We investigated the clinical significance of a vascular growth pattern of hepatocellular carcinoma (HCC), the vessels that encapsulate tumor clusters (VETC), previously linked to HCC metastatic dissemination. VETC was assessed in a large multi-institutional cohort of 541 resected HCCs from Italy, Korea and Japan, and matched against a full spectrum of clinical and pathological variables. The VETC phenotype (defined as ≥ 55% tumor area by CD34 immunostaining) was easily reproducible and reliably detectable in whole sections and small-sized tissues of tissue microarray. VETC HCCs represented 18.9% of the whole series, the lowest proportion occurring in the cohort with smallest tumors (8.7%, Japanese series). VETC was significantly associated with several clinical and pathological features such as high alfa-fetoprotein (AFP) level, tumor size greater than 5 cm, poor differentiation, macrotrabecular pattern, less compact pattern, less inflammatory infiltrates, and frequent microvascular invasion. VETC was associated with early recurrence (hazard ratio [HR]: 1.52 [1.06-2.19], P = 0.023), disease-free survival (HR: 1.66 [1.21-2.27], P = 0.002), and overall survival (HR: 2.26 [1.37-3.72], P = 0.001) at multivariable analysis. VETC affected the survival in HCC patients stratified for etiology (hepatitis C virus/hepatitis B virus), vascular invasion, and specific molecular phenotypes (β-catenin/GS+). This distinct vascular pattern was enriched in the recently reported macrotrabecular massive HCC subtype, which was seen in 7.8% (42 of 541) of patients and associated with high AFP levels and poor differentiation. Conclusion: The VETC pattern was found to be easily detectable in a consistent fraction of HCC and a powerful pathological finding affecting survival. This study suggests that the heterogeneous pattern of angiogenesis is involved in HCC behavior.

Background Indirect evidence suggesting the immunosensitivity/immunogenicity of neuroblastoma is accumulating. The aims of this study were to investigate the immune landscape of neuroblastoma and to evaluate the in vivo immunogenicity of the NY-ESO-1 tumor antigen in advanced neuroblastoma patients. Methods The immune infiltrating cells of the NY-ESO-1+ tumors from three HLA*A201 patients with metastatic neuroblastoma who relapsed after conventional treatments were evaluated by immunohistochemistry. The patients were vaccinated with the HLA-A*0201-restricted peptide NY-ESO-1157-165(V). The peptide was emulsified in Montanide ISA51 and given subcutaneously in a phase I pilot study. The immunogenicity of NY-ESO-1 antigen was evaluated by monitoring mononuclear cells in patient peripheral blood, pre- and post-vaccine, by short-term in vitro sensitization, HLA-multimer staining and IFN-γ ELISpot analysis. Results Both CD3 T cells and CD163 myeloid cells were present in pre-vaccine tumors and PD-1 and PD-L1 expression was mainly found in the immune infiltrate. Despite the advanced stage of the disease, the vaccination induced systemic NY-ESO-1 specific CD8 T cells releasing IFN-γ in response to activation with the NY-ESO-1 peptide and an HLA-A2 positive neuroblastoma cell line. Conclusions Our results indicate that vaccination with a tumor-associated peptide is able to boost NY-ESO-1-specific, functionally active T cells in advanced neuroblastoma patients with lymphocyte infiltration in their pre-vaccine tumors. Trial registration EudraCT #2006–002859-33. Electronic supplementary material The online version of this article (10.1186/s12885-018-4910-8) contains supplementary material, which is available to authorized users.

Summary HCC incidence rates have been rising in the past 3 decades and by 2025 > 1 million individuals will be affected annually. High-throughput sequencing technologies led to the identification of several molecular HCC subclasses that can be broadly grouped into 2 major subgroups, each characterized by specific morphological and phenotypical features. It is likely that this increasing knowledge and a more appropriate characterization of HCC at the pathological level will impact HCC patient management.

Rhabdomyosarcoma (RMS) represents more than 50% of paediatric soft tissue tumours. Conversely, it is extremely rare among adults, where it shows peculiar biological and clinical features that are still poorly investigated. RMS patients should be referred to a Sarcoma Centre, where the contribution of experienced radiologists plays a relevant role in the diagnostic assessment of the disease, including precise localisation, staging, image-guided biopsy, response evaluation after treatment and follow-up. Besides CT and MRI, hybrid imaging including positron emission tomography (PET)/CT and PET/MRI are giving an increasing contribution to provide functional insights about tumour biology and to improve the diagnostic accuracy of the imaging work-up. This review paper provides a revision of the pathology, clinical and radiological features of adult RMS, with a particular focus on the growing role of hybrid PET-based imaging.

Background Rhabdomyosarcomas (RMSs) are the most frequent soft tissue sarcoma in children and adolescents, defined by skeletal muscle differentiation and the status of FOXO1 fusions. In pediatric malignancies, in particular RMS, scant and controversial observations are reported about PD-L1 expression as a putative biomarker and few immune checkpoint clinical trials are conducted. Methods PD-L1 assessment was evaluated by immunohistochemistry (IHC) utilizing two anti-PDL1 antibodies, in a pilot cohort of 25 RMS. Results were confirmed in primary and commercial RMS cell lines by cytofluorimetric analysis and IHC. Results PD-L1 expression was detectable, by both anti-PD-L1 antibodies, in the immune contexture of immune cells infiltrating and/or surrounding the tumor, in 15/25 (60%) RMS, while absent expression was observed in neoplastic cells. Flow cytometry analysis and PD-L1 IHC of commercial and primary RMS cell lines confirmed a very small percentage of PD-L1 positive-tumor cells, under the detection limits of conventional IHC. Interestingly, increased PD-L1 expression was observed in the immune contexture of 4 RMS cases post chemotherapy compared to their matched pre-treatment samples. Conclusion Here we identify a peculiar pattern of PD-L1 expression in our RMS series with scanty positive-tumor cells detected by flow cytometry, and recurrent expression in the immune cells surrounding or infiltrating the tumor burden. Electronic supplementary material The online version of this article (10.1186/s12885-018-4554-8) contains supplementary material, which is available to authorized users.

Background Ossifying fibromyxoid tumor (OFMT) is a rare soft tissue neoplasm of uncertain lineage and intermediate biological potential. It is more common in middle-aged men, usually arising from the deep tissues of the extremities. It is now established that it is a translocation related tumor, most often marked by translocation of PHF1 gene. Surgery is the mainstay of treatment and proves usually curative, although, in rarer cases the disease shows malignant features and tendency to recur both locally and at distant sites. In such cases, no standard treatment exists. Case presentation We report on a case of malignant advanced OFMT of the hand with lung metastases responding to isolated limb perfusion with human recombinant tumor necrosis factor and melphalan and chemotherapy with epirubicin and ifosfamide. Conclusions To our knowledge, this is the first report of activity of soft tissue sarcoma-oriented chemotherapy in advanced OFMT.

e16554 Background: VETC has been described as an epithelial-to-mesenchymal-transition independent process of metastasis in hepatocellular carcinoma (HCC): endothelium covers small clusters of neoplastic cells allowing tumor dissemination. It has also been noted that VETC-positive HCCs benefit more from tyrosine kinase inhibitors (TKI) therapy. Interestingly, this type of angiogenesis was also found in RCC - and other cancers - and associated with poor prognosis. The objectives of the present study are: 1) to investigate the prognostic role of VETC in a cohort of primary consecutive RCC. 2) to model the predictive role VETC to TKI response in a cohort of metastatic RCC patients treated with sunitinib or pazopanib. Methods: The study was observational and retrospective. To evaluate the VETC effect on overall survival (OS) for Cox regression, with power .8, Hazard Ratio 2.35, proportion of subject VETC+ .4, proportion of events .6, correlation among covariates .4 and a type I error rate .5, the estimated sample size was n=89. We included consecutive patients undergoing surgery at our institution for primary RCC from 2005 to 2007, (Surgical Series; n=92 cases). Moreover, to investigate the possible role of VETC in predicting TKIs benefit, we considered all RCC patients treated with first line TKIs at our center (TKI Series; sunitinib, n = 39; pazopanib n = 17), and recorded the progression free survival (PFS). VETC was assessed with CD34 immunohistochemistry and defined as a continuous endothelial lining around tumor clusters. We used Bayesian probabilistic modeling to detect small effects and multilevel hierarchical modeling to reduce overfitting. Models were fit using Stan and R. The study was approved by institutional review board (n. 865/20) and registered on ClinicalTrials.gov. Results: VETC+ RCC had a worse prognosis in the Surgical Series, with a posterior probability density (PPD) of median OS of 88 months (mo) (standard deviation, SD: 16 mo) for VETC positive Vs 136 mo (SD: 26 mo) for VETC-; the expected loss of median OS was 48 mo (SD: 31 mo) for patients having a VETC + RCC. Conversely in the TKI Series, VETC+ RCC showed longer PFS compared to VETC- ones: with sunitinib a PPD of median PFS of 35 mo (SD:11 mo) for VETC+ Vs 19 mo (SD: 5 mo) for VETC-. Under Pazopanib a PPD of median PFS of 20 mo (SD: 8 mo) for VETC+ Vs 11 mo (SD: 7 mo) for VETC-. The expected gain of median PFS for of VETC+ cases, was 17 and 9 mo (SD: 12 and 11 mo), respectively in sunitinib and pazopanib treated cases. Conclusions: Our results confirmed the general adverse prognostic role of VETC in RCC, however this phenotype gave a substantial PFS gain for patients treated with TKI, similarly to what have been observed in HCC. VETC could be a new predictive bio-marker that allows the delivery of a personalized treatment: patients affected by RCC might directly benefit from a better selection of already approved drugs.

Medullary carcinoma is a rare malignant tumor of the kidney. It affects individuals of African descent and all cases reported show evidence of sickle cell trait. We reviewed an unusual carcinoma arising in a white man, the ninth in the literature. The tumor demonstrated features associated with renal medullary carcinoma, or unclassified renal cell carcinoma, medullary phenotype as recently described; the presence of sickle cell trait confirmed the diagnosis of medullary carcinoma. This case is helpful in the differential diagnosis with non-sickle cell associated “renal cell carcinoma, unclassified with medullary phenotype,” and study of this spectrum of tumors is ongoing.

11543 Background: The ceiling-drug effect seen for most active drugs in STS could be related, partially, to multidrug resistance mechanisms (MDRM). We previously reported the independent prognostic role for RFS and OS of MRP1 in high-risk localized STS of limbs and trunk-wall treated with epirubicin and ifosfamide (Mol Cancer Ther.2014 13(1):249-59). A translational study was carried out within the randomized phase III trial of epirubicin plus ifosfamide vs histotype-tailored neoadjuvant chemotherapy (NCT01710176), to investigate MRP1 prognostic value using the trial population as validation set. Methods: Patients enrolled in the trial were invited to participate, through the informed consent, to this analysis. IHC used QCRL-1 (Santa Cruz biotechnology) MRP1 monoclonal antibody. TMAs were built on the highest-grade area of each tumor, being the procedure blinded for clinical data. MRP1 expression was grouped as low (≤ 25% positive cells) vs high ( > 25% positive cells) expression. For data analysis, patients were grouped as A) epirubicin plus ifosfamide control arm and B) histotype-tailored experimental arm. Drugs used in group B were: gemcitabine-docetaxel (UPS), gemcitabine-DTIC (LMS), trabectedin (High-grade (HG) myxoid LPS), ifosfamide-etoposide (MPNST) and high-dose ifosfamide (SS). Prognostic value of MRP1’s extension was analyzed using Cox’s proportional hazard regression. A p-value < 0.05 was considered statistically significant. Results: 175 patients were analyzed (median age 49; males 61%) with median follow-up of 4.66 y. Group A (n = 88) included HG-myxoid LPS (27%), SS (25%), UPS (24%), LMS (12%) MPNST (10%) and others (2%); group B (n = 87) included UPS (38%), SS (24%), HG-myxoid LPS (20%), LMS (10%) and MPNST (8%). MRP1 high extension was distributed as follows: 48% (A) and 57% (B). High MRP-1 expression showed significantly worse prognosis for disease-free survival (DFS) (HR 2.71 (1.31-5.62) p = 0.007) and a trend towards worse OS (HR = 2.75 (0.97-7.81) p = 0.058) in group A. No correlation was seen between MRP-1 expression and DFS (p = 0.384) or OS (p = 0.665), in group B. Conclusions: MRP1 overexpression was related to significant worse prognosis in 2 prospective randomized series of high-risk, localized, STS treated with neoadjuvant epirubicin and ifosfamide. These agents are both substrate of MRP1; this could add rationale for a possible predictive role, as MDRM, for the two most active drugs in STS. A trial combining epirubicin, ifosfamide and MRP1 inhibitor is currently under design.

Item does not contain fulltext Importance: Epithelioid sarcoma (ES) is an exceedingly rare malignant neoplasm with distinctive pathologic, molecular, and clinical features as well as the potential to respond to new targeted drugs. Little is known on the activity of anthracycline-based regimens, gemcitabine-based regimens, and pazopanib in this disease. Objective: To report on the activity of anthracycline-based regimens, gemcitabine-based regimens, and pazopanib in patients with advanced ES. Design, Setting, and Participants: Seventeen sarcoma reference centers in Europe, the United States, and Japan contributed data to this retrospective analysis of patients with locally advanced/metastatic ES diagnosed between 1990 and 2016. Local pathological review was performed in all cases to confirm diagnosis according to most recent criteria. Exposures: All patients included in the study received anthracycline-based regimens, gemcitabine-based regimens, or pazopanib. Main Outcome and Measures: Response was assessed by RECIST. Progression-free survival (PFS) and overall survival (OS) were computed by Kaplan-Meier method. Classic and proximal subtypes were defined based on morphology (according to 2013 World Health Organization guidelines). Results: Overall, 115 patients were included, 80 (70%) were men and 35 (30%) were women, with a median age of 32 years (range, 15-77 years). Of the 115 patients with ES, 85 were treated with anthracycline-based regimens, 41 with gemcitabine-based regimens, and 18 with pazopanib. Twenty-four received more than 1 treatment. Median follow-up was 34 months. Response rate for anthracycline-based regimens was 22%, with a median PFS of 6 months. One complete response (CR) was reported. A trend toward a higher response rate was noticed in morphological proximal type (26%) vs classic type (19%) and in proximal vs distal primary site (26% vs 18%). The response rate for gemcitabine-based regimens was 27%, with 2 CR and a median PFS of 4 months. In this group, a trend toward a higher response rate was reported in classic vs proximal morphological type (30% vs 22%) and in distal vs proximal primary site (40% vs 14%). In the pazopanib group, no objective responses were seen, and median PFS was 3 months. Conclusions and Relevance: This is the largest retrospective series of systemic therapy in ES. We confirm a moderate activity of anthracycline-based and gemcitabine-based regimens in ES, with a similar response rate and PFS in both groups. The value of pazopanib was low. These data may serve as a benchmark for trials of novel agents in ES.

STS is a generic term that refers to a heterogeneous group of rare neoplastic diseases. The aim of this review is to discuss the role of pathology in the multidisciplinary management of STS patients. This will be done: (I) illustrating the framework for the current classification; (II) examining the characteristics that allows an expert diagnosis; (III) describing the role of the sarcoma pathologist in patient management; and (IV) discussing some of the most frequent diagnosis and their criticalities.

Extraskeletal myxoid chondrosarcoma (EMC) is an extremely rare soft tissue sarcoma, marked by a translocation involving the NR4A3 gene. EMC is usually indolent and moderately sensitive to anthracycline-based chemotherapy. Recently, we reported on the therapeutic activity of sunitinib in a series of EMC cases, however the molecular target of sunitinib in EMC is unknown. Moreover, there is still the need to identify alternative therapeutic strategies. To better characterize this disease, we performed whole transcriptome sequencing in five EMC cases. Peculiarly, in one sample, an in-frame deletion (c.1735_1737delGAT p.D579del) was identified in exon 11 of KIT. The deletion was somatic and heterozygous and was validated both at DNA and mRNA level. This sample showed a marked high expression of KIT at the mRNA level and a mild phosphorylation of the receptor. Sanger sequencing of KIT in additional 15 Formalin Fixed Paraffin Embedded (FFPE) EMC did not show any other mutated cases. In conclusion, exon 11 KIT mutation was detected only in one out of 20 EMC cases analyzed, indicating that KIT alteration is not a recurrent event in these tumors and cannot explain the EMC sensitivity to sunitinib, although it is an actionable mutation in the individual case in which it has been identified.

Perivascular epithelioid cell tumor (PEComa) is a family of mesenchymal tumors. Conventional chemotherapy has little activity in this disease, but case reports are available on the activity of mammalian target of rapamycin inhibitors (e.g. sirolimus and temsirolimus). Pharmacokinetic assays of sirolimus are available as this drug has a precise therapeutic window and blood levels might be influenced by CYP3A4 polymorphisms and drug interactions. We report on a case of a patient with metastatic, progressive PEComa who started sirolimus at a dose of 5 mg/day with evidence of grade (G) 3 mucositis, G2 thrombocytopenia, and G1 leucopenia 10 days after the treatment started, in absence of concomitant medications or prohibited food assumption. Elevated sirolimus blood levels were detected (156.8 ng/ml). Sirolimus was stopped, and toxicity resolved in 5 weeks. Computed tomography scan 2 months after the treatment started showed a partial response (RECIST). After toxicity resolution, the patient restarted sirolimus at a dose of 1 mg/day, with blood levels in the range of 10-20 ng/ml. Tumor response was confirmed and maintained, and the patient is still under treatment 18 months later, with no additional adverse effects. Genetic analysis of five selected polymorphisms (rs2740574, rs776746, rs1128503, rs2032582, and rs1045642) in drug metabolism enzymes and transporters did not provide a clear explanation of the observed unusual pharmacokinetic. This case confirms the activity of mammalian target of rapamycin inhibitors in PEComa and strengthens the importance of pharmacokinetic drug blood levels monitoring in patients treated with sirolimus. In our patient, after dose adjustment, sirolimus could be restarted with a prolonged clinical benefit and no additional toxicity.

INTRODUCTION: Retroperitoneal sarcoma (RPS) is a rare disease accounting for 0.1%–0.2% of all malignancies. Management of RPS is complex and requires multidisciplinary, tailored treatment strategies at all stages, but especially in the context of metastatic or multifocal recurrent disease. Due to the rarity and heterogeneity of this family of diseases, the literature to guide management is limited. METHODS: The Trans-Atlantic Retroperitoneal Sarcoma Working Group (TARPSWG) is an international collaboration of sarcoma experts from all disciplines convened in an effort to overcome these limitations. The TARPSWG has compiled the available evidence surrounding metastatic and multifocally recurrent RPS along with expert opinion in an iterative process to generate a consensus document regarding the complex management of this disease. The objective of this document is to guide sarcoma specialists from all disciplines in the diagnosis and treatment of multifocal recurrent or metastatic RPS. RESULTS: All aspects of patient assessment, diagnostic processes, local and systemic treatments, and palliation are reviewed in this document, and consensus recommendations provided accordingly. Recommendations were guided by available evidence, in conjunction with expert opinion where evidence was lacking. CONCLUSIONS: This consensus document combines the available literature regarding the management of multifocally recurrent or metastastic RPS with the practical expertise of high-volume sarcoma centers from multiple countries. It is designed as a tool for decision making in the complex multidisciplinary management of this condition and is expected to standardize management across centers, thereby ensuring that patients receive the highest quality care.

Background In retroperitoneal sarcoma (RPS), the optimal extent of resection must balance adequate disease control with potential for morbidity. We sought to study the frequency and outcomes after a Whipple procedure or pancreaticoduodenectomy (PD) in patients undergoing resection for primary RPS. Methods Participating referral centers within the Trans-Atlantic Retroperitoneal Sarcoma Working Group provided retrospective data from January 2007 to December 2016 for patients with primary RPS who underwent PD along with the total number of consecutive resections done during the same time period. Data from participating centers were combined for analysis. Results In total, 29 patients underwent PD among 2068 resections performed for primary RPS (1.4%). The predominant histologic subtypes were liposarcoma and leiomyosarcoma. All PD patients underwent concomitant resection of additional organs (median: 2, range: 1–5), including 13 patients (45%) who also received vena cava resection. Definitive evidence of microscopic invasion of the duodenum or pancreas was seen in 84% of patients. Postoperatively, 10 patients (34%) had major complications including 8 (28%) that developed a clinically-significant pancreatic leak. One postoperative death (3.4%) occurred. With a median follow-up of 4.8 years, 19 patients (66%) developed disease recurrence. The patterns of recurrence were dependent on histologic subtype. Conclusion Although infrequent, when PD is done for primary RPS, resection of additional organs is often required and major complication rates are moderate. The recurrence rate is overall high and the pattern of recurrence is dictated by histologic subtype.

Sarcomas represent a highly heterogeneous group of tumors as reflected in the significant overlap between their histologic phenotypes between the different types, posing diagnostic challenges for the pathologist. Definitive tumor classification is increasingly important because of prognostication and emergence of targeted therapies for some of the sarcoma types. In this review, we highlight pertinent pathologic and molecular aspects of sarcomas common in the retroperitoneum, relevant to the surgical oncologist.

Background Solitary fibrous tumour (SFT) is a rare soft tissue sarcoma with a low metastatic potential. A higher metastatic rate is observed in the high-grade/dedifferentiated variant. The most common expected site of distant spread are the lungs and the liver. Bone involvement is generally viewed as a late stage of disease spread. We report on a retrospective series of SFT patients relapsing with a single distant bone recurrence as first metastatic event, without evidence of other organ involvement. Case presentation All patients affected by a single distant bone metastasis from SFT as first distant event, without any evidence of other site of metastasis, observed at our Institution, were considered. Bone involvement from SFT was pathologically assessed in all cases and confirmed by expert pathologists. A total of six patients were retrospectively identified. Primary tumour arose from the meninges in four patients, from soft tissues in two. Bone metastases were located to the vertebrae, the hip, the acetabulum and the rib. In all cases, bone relapse was the first event, with one patient presenting a local relapse. Median time from the primary tumour and the evidence of bone relapse was 40 months (range 0–58). In 2/6 patients bone metastasis was treated with radiotherapy (RT), in 2/6 with surgery, in 2/6 with surgery plus RT. At a median follow-up of 55 months (range 23–88), 5/6 patients are alive (2/5 without disease, 3/5 with multicentric metastatic disease) and one is dead of disease. 2/6 patients did not relapse after the treatment of the bone metastasis. Conclusions This small series in a relatively rare histology suggests that isolated, possibly late, bone metastases are a plausible scenario, in particular in meningeal SFT. Notably, new bone lesions in a patient with a history of SFT should be always investigated. Exclusive local treatments may be an option, though collection of such series would be needed to define the best treatment strategy.

Background Extra-pleural and extra-meningeal solitary fibrous tumour (SFT) is a rare sarcoma histotype curable with surgery in the majority of patients. The behaviour of these tumours ranges from indolent/very low grade to malignant/high grade but it is still not possible to accurately predict prognosis after surgery. We have investigated a multi-centre series to stratify the risk of recurrence to patients with SFTs. Methods We retrospectively analysed the data from 243 patients who underwent surgery (2002–2011) at four sarcoma referral centres. Results Upon univariate analysis, hypercellularity, atypia, necrosis, high mitotic rate (ie >4 mitoses/10 HPF) were associated with both disease-free and overall survival. Surgical margins were a significant prognostic factor for disease-free (P = 0.007) but not for overall survival. Unexpectedly, larger tumour size was associated with a better prognosis (P = 0.038) and fewer recurrences (P = 0.024). Upon multivariable analysis, high mitotic rate (hazard ratio, HR = 2.85, P = 0.002), cellular atypia (HR = 1.62, P = 0.015) and hypercellularity (HR = 1.82, P = 0.031) were significantly associated with recurrences. A SFT recurrence score has been provided to stratify risk of recurrence. Conclusion This study provides a prognostic model to stratify risk of recurrence in patients with resectable SFTs. This allows clinician to decide on an optimal follow-up strategy and to select patients that may benefit from adjuvant treatments.

11566Background: Recently, we showed that the FNCLCC grading system can prognosticate the outcome of retroperitoneal LPS. We aimed to explore the impact of pathological stratification using the FNC...

e23547Background: EMC is an extremely rare soft tissue sarcoma, marked by a translocation involving NR4A3 gene. EMC are usually indolent and generally are moderately sensitive to anthracycline-base...

11561Background: EMC is a rare sarcoma mostly originating from soft tissues. EMC carries a specific translocation, involving NR4A3, which is fused more often with EWSR1 and less frequently with oth...

11074 Background: Surgery with gross margin clearance (R0 and R1) is the standard treatment for RPS and visceral resection has been proposed even in the absence of macroscopic visceral infiltration. Formal definition and margin sampling procedures for pathological evaluation are lacking for RPS. This study investigated VRM as well as viscera infiltration and their association with patient survival. Methods: Consecutive patients operated on for primary RPS (2009-2014) were extracted from a prospectively maintained database. VRM were sampled for each resected organ and classified as negative and positive. Also, tumor infiltration of resected organs was classified as follow: absence of infiltration, infiltration of perivisceral fat, early infiltration (i.e., renal/adrenal capsule, muscular fascia, contact with muscular tunica of hollow viscera), and infiltration of the viscera. Results: In 207 patients VRM were negative in 182 (88%) and positive 25 (12%). Organ infiltration was absent, perivisceral, early, and visceral in 37 (18%), 13 (6%), 17 (8%), and 140 (68%), respectively. Overall survival analysis showed that patients with negative VRM plus organ infiltration (HR = 3.56; 95%CI 1.15-11.00, P = 0.028) and those with positive VRM irrespective of organ infiltration (HR = 7.76; 95%CI 2.18-27.65, P = 0.002) did worse that patients with negative VRM plus no organ infiltration, after adjustment from known prognostic features. Conclusions: After liberal multivisceral resection for primary RPS, up to 80% of patients have infiltrated organs at some extent, while VRM are positive in up to 10% of cases. Visceral resection is justified even in the absence of macroscopic infiltration. Systematic evaluation of microscopic involvement of adjacent viscera may stratify prognosis.

4120 Background: Cutaneous Merkel cell carcinoma (MCC) is a high grade neuroendocrine carcinoma potentially induced by Merkel Cell Polyomavirus (MCPyV), a clonally integrated host in the tumor cell genome. Integration of viral DNA and truncating mutations in the helicase domain of the large T (LT) antigen, a protein implicated in the viral life cycle, have been detected in all MCPyV associated MCCs. These results suggest a role of the virus in tumor pathogenesis according to a two step model: a necessary but not sufficient integration of viral DNA followed by LT antigen premature truncations. Gastrointestinal neuroendocrine tumors (GI-NETs) share common phenotypical features with MCCs, therefore we evaluated whether MCPyVs may be present in GI-NET. Methods: Formalin–fixed and paraffin-embedded samples from 14 cases of liver metastases of G2 GI-NETs, 9 small cell lung cancer (SCLCs) and 4 MCCs of the skin were screened for MCPyV-DNA positivity using two PCR primer sets mapping the LT antigen gene. Then to confirm the putative pathogenetic role of the virus, we seeked for premature truncation of LT antigen by sequencing the helicase portion using seven amplicons mapping 1356-2210 region of the MCPyV complete genome (RefSeq: NC_010277.1). Results: Viral DNA was detected in 7/14 GI-NETs, in 0/9 SCLCs and in 4/4 MCCs. We found a premature stop codon truncating the helicase domain in two GI-NETs. Both the patients had a rapid disease progression. We also found previously not reported alterations in MCCs: a single aminoacid deletion in 3 cases and a point mutation causing a single aminoacid substitution in another case. Conclusions: For the first time the potential tumorigenic signature of MCPyV has been detected in GI-NETs, suggesting a possible role in pathogenesis. The study is ongoing to confirm these observations that could support new diagnostic and therapeutical perspectives of a subset of GI NETs. Moreover we have shown that the clonal integration of MCPyV in MCCs produces different genetic alterations with unknown effects on cell biology.