Multi-omics joint analysis revealed the metabolic profile of retroperitoneal liposarcoma.

Retroperitoneal liposarcoma (RLPS) is the main subtype of retroperitoneal soft sarcoma (RSTS) and has a poor prognosis and few treatment options, except for surgery. The proteomic and metabolic profiles of RLPS have remained unclear. The aim of our study was to reveal the metabolic profile of RLPS. Here, we performed proteomic analysis (n = 10), metabolomic analysis (n = 51), and lipidomic analysis (n = 50) of retroperitoneal dedifferentiated liposarcoma (RDDLPS) and retroperitoneal well-differentiated liposarcoma (RWDLPS) tissue and paired adjacent adipose tissue obtained during surgery. Data analysis mainly revealed that glycolysis, purine metabolism, pyrimidine metabolism and phospholipid formation were upregulated in both RDDLPS and RWDLPS tissue compared with the adjacent adipose tissue, whereas the tricarboxylic acid (TCA) cycle, lipid absorption and synthesis, fatty acid degradation and biosynthesis, as well as glycine, serine, and threonine metabolism were downregulated. Of particular importance, the glycolytic inhibitor 2-deoxy-D-glucose and pentose phosphate pathway (PPP) inhibitor RRX-001 significantly promoted the antitumor effects of the MDM2 inhibitor RG7112 and CDK4 inhibitor abemaciclib. Our study not only describes the metabolic profiles of RDDLPS and RWDLPS, but also offers potential therapeutic targets and strategies for RLPS.

Expression and function of Siglec-15 in RLPS and its correlation with PD-L1: Bioinformatics Analysis and Clinicopathological Evidence.

Purpose: Retroperitoneal liposarcoma (RLPS) is a rare malignancy without effective treatment. Since current treatment for unresectable RLPS is unsatisfactory, immunotherapy and targeted therapy are urgently needed. Siglec-15 is a transmembrane protein highly homologous to PD-L1 and is involved in tumor immune escape. The biological function of Siglec-15 in RLPS, its prognostic relevance and its relationship with PD-L1 need to be further clarified. In this study, we aimed to explore the biological function of Siglec-15 in sarcomas through bioinformatics analysis, and we also evaluated Siglec-15 and PD-L1 expression in RLPS samples. The relationship between the expression of Siglec-15 and PD-L1 and their clinicopathological relevance and prognostic value were also investigated in clinical RLPS patients. Methods: The RNA sequencing data of 259 sarcoma cases and 48 RLPS cases from TCGA were used to analyze the Siglec-15 expression and the differentially expressed genes (DEG) related with Siglec-15 expression. In addition, DEGs were subsequently analyzed through the gene ontology (GO)/ Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein-protein interaction (PPI) network. Tumor specimens were obtained from 91 RLPS patients of our sarcoma center, and Siglec-15 and PD-L1 expression were evaluated using immunohistochemistry. The correlation between the expression level of these two markers as well as their correlation with clinicopathological factors and prognosis of RLPS patients was also assessed. Results: GEPIA analysis showed that the high expression of Siglec-15 was associated with poor sarcoma OS (P=0.034). A total of 682 differential genes were identified between the high and low expression groups of Siglec-15 in RLPS. Enrichment analysis of the KEGG pathway showed that Siglec-15 was related to the Hippo signaling pathway and the neuroactive ligand-receptor interaction. GO annotation analysis showed that the expression of Siglec-15 may thus be able to affect serine hydrolase activity, alongside signal receptor activator activity. The top 5 genes with the largest number of connection points are APOA1, F2, AHSG, AMBP, SERPINC1. In subsequent studies, we used 91 liposarcoma samples from our center for verification. Siglec-15 was expressed in 84.6% of RLPS cases, whereas PD-L1 was expressed in 17.6% of RLPS cases. A negative correlation was observed between Siglec-15 and PD-L1 expression (P=0.020). In this group of RLPS patients, high Siglec-15 expression was correlated with poorer disease-free survival (DFS) (P=0.021), and it was an independent predictor of DFS (hazard ratio: 2.298; 95% confidence interval: 1.154-4.576; P=0.018). However, we did not find a correlation between PD-L1 expression and overall survival or DFS in RLPS patients. Conclusion: The DEG and signaling pathways identified in the study could provide a preliminary understanding of the underlying molecular mechanisms of Siglec-15 in the development and progression of RLPS. High expression of Siglec-15 was a negative independent predictive factor for DFS of RLPS. The negative relationship between Siglec-15 and PD-L1 expression suggested that the Siglec-15 pathway might be an important supplement to PD-L1 treatment.

Clinicopathologic Features of Retroperitoneal Malignant Solitary Fibrous Tumors.

We aimed to explore the clinicopathologic and histologic characteristics, as well as the (differential) diagnosis of retroperitoneal malignant solitary fibrous tumors (RMSFTs) in this study. Nine cases of RMSFTs were recruited and identified by an experienced pathologist from the Pathology Department of Beijing Shijitan Hospital. Clinical information was extracted from medical records and obtained by phone calls. A systematic review of published literature on RMSFTs was conducted using PubMed. A pre-specified search strategy was adopted using the key words "solitary fibrous tumor" and "retroperitoneum." Case reports and literature published in the China Academic Journals (CNKI) and WAN FANG databases were also included. In total, 58 patients (33 males and 25 females) were included; their age ranged from 17 to 83 years, with a median age of 52 years. The tumor size ranged from 4 to 36 cm, and most patients had abdominal masses and pain. Of these patients, 56 underwent surgical resection, and two patients died and underwent an autopsy. All patients were followed up for up to 288 months (with a median follow-up of 36 months). RMSFTs are extremely rare. Their diagnosis mainly relies on the histological morphology and the expression profiles of a panel of pathologic molecules measured by immunohistochemistry. Diagnosis of RMSFTs is usually based on the expression of biomarkers such as vimentin, CD34, Bcl-2, CD99, and STAT6. Differential diagnosis includes spindle-shaped cell tumors, such as schwannoma, gastrointestinal stromal tumors, dermatofibrosarcoma protuberans, synovial sarcoma, malignant peripheral nerve sheath tumors, and fibrosarcoma. RMSFTs are prone to recur and even metastasize. Complete resection remains a major treatment, and close follow-up is highly recommended.

Diagnostic and management challenges for MDM2-, CDK4-negative fatty tumors of the retroperitoneum.

BACKGROUND: Neoplasms of the retroperitoneum that contain a major fat component may represent either benign entities, such as lipomas or angiomyolipomas, or malignancy such as liposarcoma. Distinguishing these diagnoses has important implications for management. While liposarcomas often stain positively for MDM2 and CDK4 proteins, absence of these markers can lead to diagnostic and management challenges. METHODS: We examined three cases in our institution of fat-containing masses of the retroperitoneum that lacked MDM2 and CDK4 markers to highlight the challenges in diagnosing and managing these cases. A thorough review of the literature examining radiologic and histologic features that can be used to determine that diagnosis was conducted and summarized. RESULTS: The three cases we present represent the three main diagnostic entities that can be found in among fatty tumors of the retroperitoneum: lipoma, angiomyolipoma, and liposarcoma. While radiologic features and analysis of histology helped to inform management, these cases in conjunction with the literature also illustrate the limitations of the diagnostic work up and importance also factoring the biologic behavior of the tumor in its management. CONCLUSION: Fat-containing tumors of the retroperitoneum that do not stain for MDM2 or CDK4 can pose a diagnostic challenge. Assessing radiologic and pathologic features in conjunction with the biologic behavior of these tumors should inform their management.

Expression of IL4Rα and IL13Rα1 are associated with poor prognosis of soft-tissue sarcoma of the extremities, superficial trunk, and retroperitoneum.

BACKGROUND: IL4Rα and IL13Rα1 are constituents of the type II IL4 receptor. Recently, IL4Rα and IL13Rα1 were reported to have roles in cancer progression and suggested as potential prognostic markers. However, studies on IL4Rα and IL13Rα1 in soft-tissue sarcomas have been limited. METHODS: This study investigated the immunohistochemical expression of IL4Rα and IL13Rα1 in 89 soft-tissue sarcomas of the extremities, superficial trunk, and retroperitoneum. Immunohistochemical staining for IL4Rα and IL13Rα1 were scored according to a combination of staining intensity and staining area in tissue microarray samples. Positivity for the immunohistochemical expression of IL4Rα and IL13Rα1 were determined using receiver operating curve analysis. Statistical analysis was performed using regression analysis and a chi-square test. RESULTS: In human soft-tissue sarcomas, immunohistochemical expression of IL4Rα was significantly associated with IL13Rα1 expression. Nuclear and cytoplasmic expression of IL4Rα and IL13Rα1 were significantly associated with shorter survival of soft-tissue sarcoma patients in univariate analysis. Multivariate analysis indicated that nuclear expression of IL4Rα and IL13Rα1 were independent indicators of shorter overall survival (IL4Rα; p = 0.002, IL13Rα1; p = 0.016) and relapse-free survival (IL4Rα; p = 0.022, IL13Rα1; p < 0.001) of soft-tissue sarcoma patients. Moreover, the co-expression pattern of nuclear IL4Rα and IL13Rα1 was an independent indicator of shorter survival of soft-tissue sarcoma patients (overall survival; overall p < 0.001, relapse-free survival; overall p < 0.001). CONCLUSIONS: This study suggests IL4Rα and IL13Rα1 are associated with the progression of soft-tissue sarcoma, and the expression of IL4Rα and IL13Rα1 might be novel prognostic indicators of soft-tissue sarcoma patients.

11C-Metomidate PET/CT Detected Multiple Ectopic Adrenal Rest Tumors in a Woman With Congenital Adrenal Hyperplasia.

CONTEXT: Women with congenital adrenal hyperplasia (CAH) may present with androgen excess that is difficult to control with conventional suppressive doses of glucocorticoids. Clinical management is challenging, and the woman is at great risk of developing steroid-induced complications. PATIENTS AND METHODS: A 32-year-old woman with salt-wasting CAH due to 21-hydroxylase deficiency underwent right-sided adrenalectomy because of a large myelolipoma. Over the years, androgens became increasingly difficult to suppress on prednisolone 5 + 0 + 2.5 mg daily, and at age 39 years the left adrenal with an enlarging myelolipoma was removed. A month later serum testosterone levels had increased from 4.1 preoperatively to 18.3 nmol/L (reference 0.2-1.8 nmol/L), and adrenocorticotropin levels from 32 to 283 pmol/L (reference < 14 pmol/L). No adrenal parenchyma was visualized on computed tomography (CT). In the further search for the source of the markedly elevated testosterone, positron emission tomography (PET) was performed with 2 different tracers, 18fluorodeoxyglucose (18FDG) reflecting glucose metabolism and 11C-metomidate, an inhibitor of 11-ß-hydroxylase targeting adrenocortical tissue. RESULTS: 18FDG-PET/CT with cosyntropin stimulation showed ovarian/paraovarian hypermetabolism, suggestive of adrenal rest tumors. Further characterization with 11C-metomidate PET/CT showed uptakes localized to the ovaries/adnexa, behind the spleen, and between the right crus diaphragmaticus and inferior vena cava. CONCLUSION: Adrenal rest tumors can give rise to high androgen levels in spite of suppressive supraphysiological glucocorticoid doses. This case illustrates, for the first time, the value of 11C-metomidate PET as a sensitive method in documenting adrenal rest tumors, currently considered rare in women with CAH.

High Expression of microRNA-371a-3p in Cystic Fluid of Post-Chemotherapy Teratoma with Concurrent Normal Serum Levels in Patients with Non-Seminomatous Testicular Germ Cell Tumours.

BACKGROUND: MicroRNA-371a-3p (miR-371), the novel serum biomarker of testicular germ cell tumours (GCTs), is produced by undifferentiated subtypes of GCTs but not by teratoma. Cystic teratoma developing from retroperitoneal metastases of GCT subsequent to chemotherapy had been shown to contain high levels of classical serum tumour markers of GCT in the presence of normal marker levels in serum. To date, no information is available regarding the presence of miR-371 in the cystic fluid of residual teratoma after chemotherapy. METHODS: Four patients (age 18-26 years) undergoing retroperitoneal lymph node dissection (RPLND) for cystic residual masses resulting from chemotherapy of bulky retroperitoneal GCT had measurements of miR-371 in both serum and cystic fluid aspirated from surgical specimens. Measurement of the miR was performed with quantitative real-time PCR using miR-30b-5p as reference. Results were tabulated and analysed in a descriptive manner. RESULTS: Histologically, all of the surgical specimens involved teratoma only with no evidence of vital undifferentiated GCT tissue. All patients were cured. Prior to RPLND, miR-371 serum levels were not measurable or close to zero in all of the patients. Cystic fluid revealed elevated levels of miR-371 in 3 patients and traces of miR in one. CONCLUSIONS: The detection of miR-371 in the cystic fluid of teratoma is somewhat enigmatic since this GCT subtype usually does not express the miR. Two hypotheses may explain the finding: First, miR-371 molecules were released into the cystic fluid by active GCT tissue prior to chemotherapy. High levels were kept after regression of vital GCT tissue because the cystic lumen is without a specific drainage system. Second, teratoma cells lining the interior cyst wall may shed small amounts of miR-371 into the lumen. Because of the lacking drainage system, even small levels may accumulate. The present finding adds to the understanding of the biology of the novel biomarker of GCT.

A review of retroperitoneal liposarcoma genomics.

Retroperitoneal liposarcomas are rare tumours that carry a poorer prognosis than their extremity counterparts. Within their subtypes - well differentiated (WDL), dedifferentiated (DDL), myxoid (MLS) and pleomorphic (PLS) - they exhibit a diverse genomic landscape. With recent advances in next generation sequencing, the number of studies exploring this have greatly increased. The recent literature has deepened our understanding of the hallmark MDM2/CDK4 amplification in WDL/DDL and addressed concerns about toxicity and resistance when targeting this. The FUS-DDIT3 fusion gene remains the primary focus of interest in MLS with additional potential targets described. Whole genome sequencing has driven identification of novel genes and pathways implicated in WDL/DDL outside of the classic 12q13-15 amplicon. Due to their rarity; anatomical location and histologic subtype are infrequently mentioned when reporting the results of these studies. Reports can include non-adipogenic or extremity tumours, making it difficult to draw specific retroperitoneal conclusions. This narrative review aims to provide a summary of retroperitoneal liposarcoma genomics and the implications for therapeutic targeting.

Primary small intestine mesenteric low-grade fibromyxoid sarcoma with foci of atypical epithelioid whorls and diffuse DOG1 expression: a case report.

BACKGROUND: Low-grade fibromyxoid sarcoma (LGFMS) is a rare fibroblastic tumor often involving deep tissue of trunk and lower extremities in young to middle-aged patients. Rarely, LGFMS can occur in other sites including head and neck, chest, abdomen and female reproductive system. Three cases of LGFMS in mesentery of small intestine have been reported and all have conventional histologic features. Herein we reported a unique case of LGFMS in mesentery of small intestine. CASE PRESENTATION: A 43 year-old male with chief complaint of lower back pain for 4 years presented to our hospital. Physical exam reveal a firm, non-tender, non-distended, mobile large abdominal mass, which was shown on abdominal CT as a 10 cm retroperitoneal tumor. Biopsy revealed a spindle cell neoplasm in a myxoid background with a delicate vascular network. Tumor resection was performed. Gross examination of the resected specimen showed a 10.8 cm, tan-white, smooth, firm, lobulated mesenteric mass with bulging and gelatinous cut surface and confined within small bowel serosa. Microscopic examination demonstrated foci epithelioid cords and whorls with prominent atypia, in additional of regular, bland-appearing spindle cells in a fibrous and myxoid stroma and osseous metaplasia. The tumor cells stained diffusely positive for DOG1 with moderate staining density, and diffusely and strongly positive for MUC4. Rearrangement involving FUS (16p11.2) gene was identified with break-apart probe and confirmed by Anchored Multiplex PCR. A final diagnosis of low-grade fibromyxoid sarcoma was rendered. CONCLUSION: Our case highlights the importance of including LGFMS in the differential diagnosis of mesenteric tumors and the DOG1 positivity which could represent a potential diagnostic pitfall.

Uncommon Localization of Extrarenal Xp11.2 Translocation-associated Renal Cell Carcinoma (RCC): Case Report.

The World Health Organization has recognized Xp11.2 translocation-associated renal cell carcinoma (RCC) as a distinct neoplasm that arises within the kidney. Although many reports of extrarenal carcinoma may be found in the literature, to the best of our knowledge, Xp11 translocation-associated RCC with intact kidneys has not been documented. This report describes a multilobulated right retroperitoneal soft tissue mass (7.9×5.3×12.6 cm) of a 37-year-old man complaining of abdominal pain in the right side. The patient underwent a computed tomography-guided biopsy. Microscopic evaluation reveals a tumor with papillary and sheaths architectures with cells revealing clear to eosinophilic cytoplasm. Immunohistochemical evaluation on the biopsy reveals that the tumor is positive for PAX-8, CD10, and TFE3. It is negative for CK7, EMA, Vimentin, RCC, CK8/18, D20, CD3, PLAP, OCT4, CD30, MART-1, Inhibin, S-100, HMB-45, Desmin, SMA, and DOG-1. The diagnosis was malignant epithelioid neoplasm and the diagnosis of translocation RCC was suggested. Excision was recommended. The patient underwent right radical nephrectomy with removal of this large mass. Pathologic examination showed a large cystic and solid, nonhomogenous mass with some necrotic areas, originating from the perirenal fat between the adrenal gland and the kidney. Microscopic features showed a tumor with papillary, rhabdoid, and clear cell features. Immunohistochemical stains showed that the tumor cells positively expressed AMACR, PAX-8, CD10, RCC, and TFE3, but were negative for cytokeratins, vimentin, HMB-45, desmin, SMA, EMA, and MSA. Cytogenetic studies confirmed the diagnosis of Xp11.2 translocation-associated RCC with positive TFE3 gene rearrangement. To the best of our knowledge, this type of extrarenal tumor has never been reported.

18F-NaF Uptake in Retroperitoneal Neurofibroma and Uterine Leiomyoma Calcifications.

A 48-year-old woman with intermittent lower back pain for 9 months and known retroperitoneal neurofibroma underwent F-NaF PET/CT scan to assess possible bony lesions causing the pain. Incidentally, the images showed elevated NaF activity in the retroperitoneal neurofibroma. In addition, uterine leiomyoma with heterogeneous calcifications revealed increased NaF activity.

Linc00423 as a tumor suppressor in retroperitoneal liposarcoma via activing MAPK signaling pathway through destabilizing of NFATC3.

Unraveling the noncoding RNA expression networks governing cancer initiation and development is essential while remains largely uncompleted in retroperitoneal liposarcoma (RLS). Through RNA-seq technologies and computational biology, deregulated long noncoding RNAs (lncRNAs) are being identified and reveal that lncRNAs are implicated in serial steps of RLS development. High-throughput sequencing with computational methods for assembling the transcriptome of five paired RLS patient's tissues. We found that long intergenic noncoding RNA 423 (linc00423) was downregulated in RLS tissues. Gain-of-function assays revealed that overexpressed linc00423 obviously inhibited RLS cell growth in vitro and in vivo. Additionally, RNA sequence, RNA-pulldown and RIP assays evidenced that linc00423 involved in MAPK signaling pathway via destabilizing of nuclear factor of activated T-cells 3 (NFATC3). Summing up, our findings demonstrated that linc00423 acted as the tumor suppressor in RLS cells through regulating the protein level of NFATC3 at a post-transcriptional level and negatively regulated the MAPK signaling pathway at a transcriptional level. Linc00423 might serve as a candidate prognostic biomarker and a target for novel therapies of RLS patients.

The use of pharmacokinetically guided carboplatin chemotherapy in a pre-term infant with neuroblastoma-associated spinal cord compression.

Neonatal neuroblastoma may require chemotherapy either due to mass effect or unfavourable cytogenetics. This case focuses on using pharmacokinetic (PK) guided chemotherapy to treat neonatal neuroblastoma. A newborn baby was noted to have left leg immobility. Imaging showed a retroperitoneal tumour with spinal canal extension causing spinal cord compression. PK-guided carboplatin was given after conventionally dosed chemotherapy demonstrated no improvement. After initiation of PK therapy, clinical and radiological improvement was seen. We discuss our decision to use PK-guided chemotherapy despite guidelines recommending weight-based dosing and discuss the benefits in terms of clinical efficacy without increased toxicity.

Variable somatostatin receptor subtype expression in 151 primary pheochromocytomas and paragangliomas.

Pheochromocytomas (PHEOs) and paragangliomas (PGLs) are neuroendocrine tumors that express somatostatin receptors (SSTRs), a phenomenon that constitutes a basis for tumor imaging and treatment with somatostatin analogues and peptide receptor radionuclide therapy. We studied the immunohistochemical expression of SSTR1-5 in 151 primary tumors, including 14 metastasized and 16 SDHB-deficient tumors. SSTR2 and SSTR3 were most abundantly present in these tumors, whereas the tumors were mostly negative for SSTR1, SSTR4, and SSTR5. All metastasized PGLs (9/9), but only one metastasized PHEO (1/5), were strongly SSTR2 positive. SSTR3 expression was lower in metastatic tumors and tumors with a high proliferation rate (MIB1 ≥ 5%), but tumors had variable individual SSTR profiles. No correlation was found between SDHB status and SSTR expression. Our results suggest that new SSTR analogues with affinity for several SSTRs could be relevant for a subgroup of patients with these tumors. Better knowledge of tumor SSTR profiles could open the door for personalized imaging and treatment in the future. Because SSTR profiles vary in PHEOs and PGLs, individual analysis is required for each tumor.

[Prognostic factors analysis of Ki-67, α-SMA expression in retroperitoneal leiomyosarcoma].

Objective: To investigate the expression and prognostic value of alpha smooth muscle actin(α-SMA) and Ki-67 in retroperitoneal leiomyosarcoma. Methods: Fifty retroperitoneal leiomyosarcoma patients who underwent operation in Chinese People's Liberation Army General Hospital from May 2002 to December 2015 were retrospectively analyzed. There were 14 males and 36 females form 21 to 79 and an average age of 48. Kaplan-Meier estimations and Cox regression analyses were performed. Results: Of the 50 cases, 45 patients underwent complete resection, and others are not. The overall 1, 3, 5-year survival rates were 86.0%, 46.0% and 28.0%, respectively. Tumor size, extent of resection, pathological stage, and expression levels of Ki-67 and alpha smooth muscle actin (α-SMA) were closely related to the survival of retroperitoneal leiomyosarcoma patients (all P<0.05), respectively. Multivariate analysis showed that pathological grade and degree of surgical resection were independent risk factors in the prognosis of patients (P<0.05). Conclusion: The high expression of α-SMA and Ki-67 are indicators of poor prognosis in retroperitoneal leiomyosarcoma, which can be used as a potential survival predictor in patients with retroperitoneal leiomyosarcoma.

Clinicopathological and Molecular Factors, Risk Factors, Treatment Outcomes and Risk of Recurrence in Mesenteric and Retroperitoneal Extragastrointestinal Stromal Tumors.

BACKGROUND/AIM: The objective of the present study was to determine the clinicopathological factors and treatment outcomes of patients suffering from mesenteric or retroperitoneal extragastrointestinal stromal tumors (EGISTs). MATERIALS AND METHODS: A detailed search in PubMed, using the key words "extragastrointestinal stromal tumors" and "EGIST", found eight studies fulfilling the criteria of this study. RESULTS: Thirty-six patients with a mesenteric and 24 patients with a retroperitoneal EGIST were analyzed, with a follow-up period ranging from 2 to 192 months. Retroperitoneal tumors presented as larger tumors than mesenteric ones, with 95% and 93% immunohistochemical positivity for CD117 antigen, respectively. Surgical resection was performed in 91% of cases, with 57% of patients with mesenteric and 70% of patients with retroperitoneal EGISTs being alive at the last follow-up. CONCLUSION: EGISTs most commonly are of considerable size and usually with a high mitotic count, rendering them high-risk tumors. Tumor necrosis, nuclear atypia, tumor histology, and mutations in the tyrosine kinase KIT or platelet-derived growth factor receptor A (PDGFRA) gene, seem to influence tumor behavior.

Abdominopelvic and Retroperitoneal Low-Grade Fibromyxoid Sarcoma: A Clinicopathologic Study of 13 Cases.

OBJECTIVES: Low-grade fibromyxoid sarcoma (LGFMS) is a rare tumor often arising in the lower extremities. Only rare examples in the abdominal cavity, pelvis, and retroperitoneum have been reported. METHODS: cases of abdominopelvic and retroperitoneal LGFMS were retrieved. MUC4, Actin, ALK, ß-catenin, desmin, DOG1, KIT, S100 protein, and STAT6 testing was performed, and a subset was tested for FUS rearrangement. RESULTS: Sites included intra-abdominal/abdominal wall (four cases), retroperitoneum (three cases), pelvis (three cases), small bowel (two cases), and kidney (one case) (median size, 15 cm; age range, 5-61 years). Tumors harbored spindled cells with mild to moderate atypia, displaying alternating myxoid nodules and hyalinized areas. All cases were positive for MUC4, and five (of five) cases tested harbored FUS rearrangement. Variable positivity for DOG1 (four of 10) and actin (two of 10) was identified. Six tumors recurred, and one patient developed metastasis. CONCLUSION: LGFMS arising in these central locations exhibits similar clinicopathologic features to its counterpart in the extremities. LGFMS at these sites may show limited immunoreactivity for DOG1 and actin.