Chemical and Physical Characterisation of Macroaggregated Human Serum Albumin: Strength and Specificity of Bonds with 99mTc and 68Ga.

BACKGROUND: Macroaggregated human serum albumin (MAA) properties are widely used in nuclear medicine, labelled with 99mTc. The aim of this study is to improve the knowledge about the morphology, size, dimension and physical-chemical characteristics of MAA and their bond with 99mTc and 68Ga. METHODS: Commercial kits of MAA (Pulmocis®) were used. Characterisation through experiments based on SEM, DLS and Stokes' Law were carried out. In vitro experiments for Langmuir isotherms and pH studies on radiolabelling were performed and the stability of the radiometal complex was verified through competition reactions. RESULTS: The study settles the MAA dimension within the range 43-51 µm. The Langmuir isotherm reveals for [99mTc]MAA: Bmax (46.32), h (2.36); for [68Ga]MAA: Bmax (44.54), h (0.893). Dual labelling reveals that MAA does not discriminate different radioisotopes. Experiments on pH placed the optimal pH for labelling with 99mTc at 6. CONCLUSION: Radiolabelling of MAA is possible with high efficiency. The nondiscriminatory MAA bonds make this drug suitable for radiolabelling with different radioisotopes or for dual labelling. This finding illustrates the need to continue investigating MAA chemical and physical characteristics to allow for secure labelling with different isotopes.

Pancreatic serous cystoadenoma (CSA) showing increased tracer uptake at 68-GaDOTA-peptide Positron Emission Tomography (68Ga-DOTA-peptide PET-CT): a case report.

BACKGROUND: Serous cysto-adenoma (SCA) is a rare benign neoplasm of the pancreas. SCA can mimic other pancreatic lesions, such as neuroendocrine tumours. 68Gallium-DOTA-peptide Positron Emission Tomography (PET) is able to image in vivo the over-expression of the somatostatin receptors, playing an important role for the identification of neuroendocrine neoplasms. CASE PRESENTATION: We reported a case of 63-year-old man, with a solid lesion of 7 cm of diameter of the body-tail of the pancreas. Two fine-needle-aspirations (FNA) were inconclusive. A 68Ga-DOTA-peptide PET-CT revealed a pathological uptake of the pancreatic lesion. The diagnosis of a pancreatic neuroendocrine neoplasm was established and a laparoscopic distal splenopancreatectomy and cholecystectomy was performed. Final histopathological report revealed the presence of a micro-cystic SCA. CONCLUSIONS: The current case firstly reports a pancreatic SCA showing increased radiopharmaceutical uptake at 68Ga-DOTA-peptide PET-CT images. This unexpected finding should be taken into account during the diagnostic algorithm of a pancreatic lesion, in order to minimize the risk of misdiagnosis and overtreatment of SCA.

Performance of FDG-PET/CT in solitary pulmonary nodule based on pre-test likelihood of malignancy: results from the ITALIAN retrospective multicenter trial.

PURPOSE: The aim of this study was to determine the performance of 18F-FDG-PET/CT in patients with solitary pulmonary nodule (SPN), stratifying the risk according to the likelihood of pulmonary malignancy. METHODS: FDG-PET/CT of 502 patients, stratified for pre-test cancer risk, were retrospectively analyzed. FDG uptake in SPN was assessed by a 4-point scoring system and semiquantitative analysis using the ratio between SUVmax in SPN and SUVmean in mediastinal blood pool (BP) and between SUVmax in SPN and SUVmean in liver (L). Histopathology and/or follow-up data were used as standard of reference. RESULTS: SPN was malignant in 180 (36%) patients, benign in 175 (35%), and indeterminate in 147 (29%). The 355 patients with a definitive SPN nature (malignant or benign) were considered for the analysis. Considering FDG uptake ≥ 2, sensitivity, specificity, positive (PPV) and negative (NPV) predictive values, and accuracy were 85.6%, 85.7%, 86%, 85.2%, and 85.6% respectively. Sensitivity and PPV were higher (P < 0.05) in intermediate and high-risk patients, while specificity and NPV were higher (P < 0.05) in low-risk patients. On receiver operating characteristic curve analysis, the cut-offs for better discrimination between benign and malignant SPN were 1.56 (sensitivity 81% and specificity 87%) and 1.12 (sensitivity 81% and specificity 86%) for SUVmax/SUVmeanBP and SUVmax/SUVmeanL respectively. In intermediate and high-risk patients, including the SUVmax/SUVmeanBP, the specificity shifted from 85% and 50% to 100%. CONCLUSION: Visual FDG-PET/CT has an acceptable performance in patients with SPN, but accuracy improves when SUVratios are considered, particularly in patients with intermediate and high risk of malignancy.

Risk-related 18F-FDG PET/CT and new diagnostic strategies in patients with solitary pulmonary nodule: the ITALIAN multicenter trial.

PURPOSE: Diagnosis of solitary pulmonary nodule (SPN) is an important public health issue and 18F-FDG PET/CT has proven to be more effective than CT alone. Pre-test risk stratification and clinical presentation of SPN could affect the diagnostic strategy. A relevant issue is whether thoracic segmental (s)-PET/CT could be implemented in patients with SPN. This retrospective multicenter study compared the results of FDG whole-body (wb)-PET/CT to those of s-PET/CT. METHODS: 18F-FDG PET/CT of 502 patients, stratified for pre-test cancer risk, were retrospectively analyzed. The thoracic part of wb-PET/CT, considered s-PET/CT, was compared to wb-PET/CT. Clinical and PET/CT variables were investigated for SPN characterization as well as for identification of patients in whom s-PET/CT could be performed. Histopathology or follow-up data were used as a reference. RESULTS: In the study population, 36% had malignant, 35% benign, and 29% indeterminate SPN. 18F-FDG uptake indicative of thoracic and extra-thoracic lesions was detectable in 13% and 3% of the patients. All patients with extra-thoracic metastases (n = 13) had thoracic lymph node involvement and highest 18F-FDG uptake at level of SPN (negative predictive value 100%). Compared to wb-PET/CT, s-PET/CT could save about 2/3 of 18F-FDG dose, radiation exposure or scan-time, without affecting the clinical impact of PET/CT. CONCLUSION: Pre-test probability of malignancy can guide the diagnostic strategy of 18FDG-PET/CT in patients with SPN. In subjects with low-intermediate pretest probability s-PET/CT imaging might be planned in advance, while in those at high risk and with thoracic lymph node involvement a wb-PET/CT is necessary.

Selective proliferative response of microglia to alternative polarization signals.

BACKGROUND: Microglia are resident myeloid cells of the central nervous system (CNS) that are maintained by self-renewal and actively participate in tissue homeostasis and immune defense. Under the influence of endogenous or pathological signals, microglia undertake biochemical transformations that are schematically classified as the pro-inflammatory M1 phenotype and the alternatively activated M2 state. Dysregulated proliferation of M1-activated microglia has detrimental effects, while an increased number of microglia with the alternative, pro-resolving phenotype might be beneficial in brain pathologies; however, the proliferative response of microglia to M2 signals is not yet known. We thus evaluated the ability of interleukin-4 (IL-4), a typical M2 and proliferative signal for peripheral macrophages, to induce microglia proliferation and compared it with other proliferative and M2 polarizing stimuli for macrophages, namely colony-stimulating factor-1 (CSF-1) and the estrogen hormone, 17ß-estradiol (E2). METHODS: Recombinant IL-4 was delivered to the brain of adult mice by intracerebroventricular (i.c.v.) injection; whole brain areas or ex vivo-sorted microglia were analyzed by real-time PCR for assessing the mRNA levels of genes related with cell proliferation (Ki67, CDK-1, and CcnB2) and M2 polarization (Arg1, Fizz1, Ym-1) or by FACS analyses of in vivo BrdU incorporation in microglia. Primary cultures of microglia and astrocytes were also tested for proliferative effects. RESULTS: Our results show that IL-4 only slightly modified the expression of cell cycle-related genes in some brain areas but not in microglia, where it strongly enhanced M2 gene expression; on the contrary, brain delivery of CSF-1 triggered proliferation as well as M2 polarization of microglia both in vivo and in vitro. Similar to IL-4, the systemic E2 administration failed to induce microglia proliferation while it increased M2 gene expression. CONCLUSIONS: Our data show that, in contrast to the wider responsiveness of peripheral macrophages, microglia proliferation is stimulated by selected M2 polarizing stimuli suggesting a role for the local microenvironment and developmental origin of tissue macrophages in regulating self-renewal following alternative activating stimuli.

Heterogeneous induction of microglia M2a phenotype by central administration of interleukin-4.

BACKGROUND: Acquisition of the M1 or M2 phenotypes by microglia has been shown to occur during the development of pathological conditions, with M1 activation being widely involved in neurotoxicity in relation with the anatomical localization and the reactivity of subtypes of microglia cells. On the contrary, little is known on the ability of microglia to undergo M2 polarization by interleukin-4 (IL4), the typical M2a polarization signal for peripheral macrophages. METHODS: Recombinant mouse IL4 was injected in the third cerebral ventricle of mice to induce brain alternative polarization. The mRNA levels of Fizz1, Arg1, and Ym1 genes, known to be up-regulated by IL4 in peripheral macrophages, together with additional polarization markers, were evaluated in the striatum and frontal cortex at different time intervals after central administration of IL4; in parallel, M2a protein expression was evaluated in tissue extracts and at the cellular level. RESULTS: Our results show that the potency and temporal profile of IL4-mediated M2a gene induction vary depending on the gene analyzed and according to the specific brain area analyzed, with the striatum showing a reduced M2a response compared with the frontal cortex, as further substantiated by assays of polarization protein levels. Of notice, Fizz1 mRNA induction reached 100-fold level, underscoring the potency of this specific IL4 signaling pathway in the brain. In addition, immunochemistry assays demonstrated the localization of the M2 response specifically to microglia cells and, more interestingly, the existence of a subpopulation of microglia cells amenable to undergoing M2a polarization in the healthy mouse brain. CONCLUSIONS: These results show that the responsiveness of brain macrophages to centrally administered IL4 may vary depending on the gene and brain area analyzed, and that M2a polarization can be ascribed to a subpopulation of IL4-responsive microglia cells. The biochemical pathways that enable microglia to undergo M2a activation represent key aspects for understanding the physiopathology of neuroinflammation and for developing novel therapeutic and diagnostic agents.

Prostate-Specific Membrane Antigen Positron Emission Tomography Oncological Applications beyond Prostate Cancer in Comparison to Other Radiopharmaceuticals.

BACKGROUND: Prostate-specific membrane antigen (PSMA) is a type II transmembrane glycoprotein overexpressed on the surface of tumor cells in most of the patients affected by prostate adenocarcinoma (PCa). However, PSMA expression has also been demonstrated in the endothelial cells of newly formed vessels of various solid tumors, suggesting a role for PSMA in neoangiogenesis. In this scenario, gallium-68 (68Ga) or fluoro-18 (18F)-labeled PSMA positron emission tomography (PET) may play a role in tumors other than PCa, generally evaluated employing other radiopharmaceuticals targeting different pathways. This review aims to investigate the detection rate of PSMA-PET compared to other radiopharmaceuticals (especially [18F]FDG) in non-prostate tumors to identify patients who may benefit from the use of such a theragnostic agent. METHODS: We performed a bibliographic search on three different databases until February 2024 using the following terms: "positron emission tomography", "PET", "PET/CT", "Prostate-specific membrane antigen", "PSMA", "non-prostate", "not prostate cancer", "solid tumor", "FDG", "Fluorodeoxyglucose", "FAPi", "FET", "MET", "DOPA", "choline", "FCH", "FES", "DOTATOC", "DOTANOC", and "DOTATATE". Only original articles edited in English with at least 10 patients were included. RESULTS: Out of a total of 120 articles, only 25 original articles comparing PSMA with other radiotracers were included in this study. The main evidence was demonstrated in renal cell carcinoma, where PSMA showed a higher detection rate compared to [18F]FDG PET/CT, with implications for patient management. PSMA PET may also improve the assessment of other entities, such as gliomas, in defining regions of early neoangiogenesis. Further data are needed to evaluate the potential role of PSMA-PET in triple-negative breast cancer as a novel therapeutic vascular target. Finally, unclear applications of PSMA-PET include thyroid and gastrointestinal tumors. CONCLUSIONS: The present review shows the potential use of PSMA-labeled PET/CT in solid tumors beyond PCa, underlining its value over other radiopharmaceuticals (mainly [18F]FDG). Prospective clinical trials with larger sample sizes are crucial to further investigate these possible clinical applications.

The immune activity of selective estrogen receptor modulators is gene and macrophage subtype-specific yet converges on Il1b downregulation.

Raloxifene belongs to the family of Selective Estrogen Receptor Modulators (SERMs), which are drugs widely prescribed for Estrogen Receptor alpha (ERα)-related pathologies. Recently, SERMs are being tested in repurposing strategies for ERα-independent clinical indications, including a wide range of microbial infections. Macrophages are central in the fight against pathogen invasion. Despite estrogens have been shown to regulate macrophage phenotype, SERMs activity in these cells is still poorly defined. We investigated the activity of Raloxifene in comparison with another widely used SERM, Tamoxifen, on immune gene expression in macrophages obtained from mouse and human tissues, including mouse peritoneal macrophages, bone marrow-derived macrophages, microglia or human blood-derived macrophages, assaying for the involvement of the ERα, PI3K and NRF2 pathways also under inflammatory conditions. Our data demonstrate that Raloxifene acts by a dual mechanism, which entails ERα antagonism and off-target mediators. Moreover, micromolar concentrations of Raloxifene increase the expression of immune metabolic genes, such as Vegfa and Hmox1, through PI3K and NRF2 activation selectively in peritoneal macrophages. Conversely, Il1b mRNA down-regulation by SERMs is consistently observed in all macrophage subtypes and unrelated to the PI3K/NRF2 system. Importantly, the production of the inflammatory cytokine TNFα induced by the bacterial endotoxin, LPS, is potentiated by SERMs and paralleled by the cell subtype-specific increase in IL1ß secretion. This work extends our knowledge on the biological and molecular mechanisms of SERMs immune activity and indicate macrophages as a pharmacological target for the exploitation of the antimicrobial potential of these drugs.

Somatostatin receptor SPECT.

Somatostatin is a peptide with a broad distribution in the nervous system and acts as a neurotransmitter in several organs, having a wide range of mainly inhibiting effects, such as the suppression of growth hormone release, as well as the inhibition of pancreatic and gastrointestinal hormone release. Five somatostatin receptor subtypes have been cloned and demonstrated to have an emphasized expression in all human tumours. In particular, type 2 receptors were identified as the most frequently represented on the surface of neuroendocrine tumour cells, providing the molecular basis for many clinical applications of somatostatin analogues. Towards the end of the 1980s, the in vivo demonstration of somatostatin receptors on the surface of some tumours raised interest in receptor imaging, and indeed the peptide receptor overexpression on tumour cells, as compared to normal tissues, constitutes the basis for molecular imaging of these tumours. This review intends to illustrate the development of single photon emission radiopharmaceuticals for the study of somatostatin receptors and their application in diagnostic imaging.

Tamoxifen Twists Again: On and Off-Targets in Macrophages and Infections.

Beyond the wide use of tamoxifen in breast cancer chemotherapy due to its estrogen receptor antagonist activity, this drug is being assayed in repurposing strategies against a number of microbial infections. We conducted a literature search on the evidence related with tamoxifen activity in macrophages, since these immune cells participate as a first line-defense against pathogen invasion. Consistent data indicate the existence of estrogen receptor-independent targets of tamoxifen in macrophages that include lipid mediators and signaling pathways, such as NRF2 and caspase-1, which allow these cells to undergo phenotypic adaptation and potentiate the inflammatory response, without the induction of cell death. Thus, these lines of evidence suggest that the widespread antimicrobial activity of this drug can be ascribed, at least in part, to the potentiation of the host innate immunity. This widens our understanding of the pharmacological activity of tamoxifen with relevant therapeutic implications for infections and other clinical indications that may benefit from the immunomodulatory effects of this drug.

Matched pairs dosimetry: 124I/131I metaiodobenzylguanidine and 124I/131I and 86Y/90Y antibodies.

The technological advances in imaging and production of radiopharmaceuticals are driving an innovative way of evaluating the targets for antineoplastic therapies. Besides the use of imaging to better delineate the volume of external beam radiation therapy in oncology, modern imaging techniques are able to identify targets for highly specific medical therapies, using chemotherapeutic drugs and antiangiogenesis molecules. Moreover, radionuclide imaging is able to select targets for radionuclide therapy and to give the way to in vivo dose calculation to target tissues and to critical organs. This contribution reports the main studies published on matched pairs dosimetry with (124)I/(131)I- and (86)Y/(90)Y-labelled radiopharmaceuticals, with an emphasis on metaiodobenzylguanidine (MIBG) and monoclonal antibodies.

Dietary essential amino acids restore liver metabolism in ovariectomized mice via hepatic estrogen receptor α.

In female mammals, the cessation of ovarian functions is associated with significant metabolic alterations, weight gain, and increased susceptibility to a number of pathologies associated with ageing. The molecular mechanisms triggering these systemic events are unknown because most tissues are responsive to lowered circulating sex steroids. As it has been demonstrated that isoform alpha of the estrogen receptor (ERα) may be activated by both estrogens and amino acids, we test the metabolic effects of a diet enriched in specific amino acids in ovariectomized (OVX) mice. This diet is able to block the OVX-induced weight gain and fat deposition in the liver. The use of liver-specific ERα KO mice demonstrates that the hepatic ERα, through the control of liver lipid metabolism, has a key role in the systemic response to OVX. The study suggests that the liver ERα might be a valuable target for dietary treatments for the post-menopause.

ERα-independent NRF2-mediated immunoregulatory activity of tamoxifen.

Sex differences in immune-mediated diseases are linked to the activity of estrogens on innate immunity cells, including macrophages. Tamoxifen (TAM) is a selective estrogen receptor modulator (SERM) used in estrogen receptor-alpha (ERα)-dependent breast cancers and off-target indications such as infections, although the immune activity of TAM and its active metabolite, 4-OH tamoxifen (4HT), is poorly characterized. Here, we aimed at investigating the endocrine and immune activity of these SERMs in macrophages. Using primary cultures of female mouse macrophages, we analyzed the expression of immune mediators and activation of effector functions in competition experiments with SERMs and 17ß-estradiol (E2) or the bacterial endotoxin LPS. We observed that 4HT and TAM induce estrogen antagonist effects when used at nanomolar concentrations, while pharmacological concentrations that are reached by TAM in clinical settings regulate the expression of VEGFα and other immune activation genes by ERα- and G protein-coupled receptor 1 (GPER1)-independent mechanisms that involve NRF2 through PI3K/Akt-dependent mechanisms. Importantly, we observed that SERMs potentiate cell phagocytosis and modify the effects of LPS on the expression of inflammatory cytokines, such as TNFα and IL1ß, with an overall increase in cell inflammatory phenotype, further sustained by potentiation of IL1ß secretion through caspase-1 activation. Altogether, our data unravel a novel molecular mechanism and immune functions for TAM and 4HT, sustaining their repurposing in infective and other estrogen receptors-unrelated pathologies.

131I/123I-metaiodobenzylguanidine (mIBG) scintigraphy: procedure guidelines for tumour imaging.

The aim of this document is to provide general information about mIBG scintigraphy in cancer patients. The guidelines describe the mIBG scintigraphy protocol currently used in clinical routine, but do not include all existing procedures for neuroendocrine tumours. The guidelines should therefore not be taken as exclusive of other nuclear medicine modalities that can be used to obtain comparable results. It is important to remember that the resources and facilities available for patient care may vary from one country to another and from one medical institution to another. The present guidelines have been prepared for nuclear medicine physicians and intend to offer assistance in optimizing the diagnostic information that can currently be obtained from mIBG scintigraphy. The corresponding guidelines of the Society of Nuclear Medicine (SNM) and the Dosimetry, Therapy and Paediatric Committee of the EANM have been taken into consideration, and partially integrated into this text. The same has been done with the most relevant literature on this topic, and the final result has been discussed within a group of distinguished experts.

Procedure guidelines for PET/CT tumour imaging with 68Ga-DOTA-conjugated peptides: 68Ga-DOTA-TOC, 68Ga-DOTA-NOC, 68Ga-DOTA-TATE.

The aim of these guidelines is to assist nuclear medicine physicians in recommending, performing, reporting and interpreting the results of somatostatin (SST) receptor PET/CT imaging using 68Ga-DOTA-conjugated peptides, analogues of octreotide, that bind to SST receptors. This imaging modality should not be regarded as the only approach to visualizing tumours expressing SST receptors or as excluding other imaging modalities useful for obtaining comparable results. The corresponding guidelines of 111In-pentetreotide scintigraphy imaging have been considered and partially integrated with this text. The same has been done with the relevant and recent literature in this field and the final result has been discussed by distinguished experts.

111In-pentetreotide scintigraphy: procedure guidelines for tumour imaging.

This document provides general information about somatostatin receptor scintigraphy with (111)In-pentetreotide. This guideline should not be regarded as the only approach to visualise tumours expressing somatostatin receptors or as exclusive of other nuclear medicine procedures useful to obtain comparable results. The aim of this guideline is to assist nuclear medicine physicians in recommending, performing, reporting and interpreting the results of (111)In-pentetreotide scintigraphy.

Reciprocal interference between the NRF2 and LPS signaling pathways on the immune-metabolic phenotype of peritoneal macrophages.

The metabolic and immune adaptation to extracellular signals allows macrophages to carry out specialized functions involved in immune protection and tissue homeostasis. Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that coordinates cell redox and metabolic responses to stressors. However, the individual and concomitant activation of NRF2 and inflammatory pathways have been poorly investigated in isolated macrophages. We here took advantage of reporter mice for the transcriptional activities of NRF2 and nuclear factor-kB (NFκB), a key transcription factor in inflammation, and observe a persisting reciprocal interference in the response of peritoneal macrophages to the respective activators, tert-Butylhydroquinone (tBHQ) and lipopolysaccharide (LPS). When analyzed separately by gene expression studies, these pathways trigger macrophage-specific metabolic and proliferative target genes that are associated with tBHQ-induced pentose phosphate pathway (PPP) with no proliferative response, and with opposite effects observed with LPS. Importantly, the simultaneous administration of tBHQ + LPS alters the effects of each individual pathway in a target gene-specific manner. In fact, this co-treatment potentiates the effects of tBHQ on the antioxidant enzyme, HMOX1, and the antibacterial enzyme, IRG1, respectively; moreover, the combined treatment reduces tBHQ activity on the glycolytic enzymes, TALDO1 and TKT, and decreases LPS effects on the metabolic enzyme IDH1, the proliferation-related proteins KI67 and PPAT, and the inflammatory cytokines IL-1ß, IL-6, and TNFα. Altogether, our results show that the activation of NRF2 redirects the metabolic, immune, and proliferative response of peritoneal macrophages to inflammatory signals, with relevant consequences for the pharmacological treatment of diseases that are associated with unopposed inflammatory responses.

Morphometric vertebral fractures in patients with castration-resistant prostate cancer undergoing treatment with radium-223: a longitudinal study in the real-life clinical practice.

PURPOSE: Radium-223 was associated with high incidence of non-vertebral fractures in patients with castration-resistant prostate cancer (CRPC). However, it is still unclear whether radium-223 may induce skeletal fragility regardless of other therapies for CRPC. We aimed at evaluating the prevalence, incidence, and determinants of vertebral fractures (VFs), i.e., the most frequent complication of skeletal fragility, in CRCP patients undergoing radium-223 therapy in the real-life clinical practice. METHODS: We retrospectively reviewed 49 CRPC patients with symptomatic bone metastases treated with radium-223. Patients received median number of four radium-223 doses (range: 2-6) and were followed-up for a median period of 11 months (range: 6-44). VFs were assessed by a quantitative morphometry using lateral images of spine 11C-Choline PET/CT, excluding from the analysis the vertebral bodies affected by bone metastases. RESULTS: Before radium-223 administration, 24 patients (49%) had VFs significantly associated with duration of androgen deprivation therapy (ADT; odds ratio 1.29) and previous abiraterone therapy (odds ratio 3.80). During radium-223 therapy, incident VFs occurred in 25% of patients, in relationship with prevalent VFs (hazard ratio 6.89) and change in serum total alkaline phosphatase values (hazard ratio 0.97), whereas the correlations with ADT and abiraterone therapy were lost. Noteworthy, the risk of VFs did not correlate with the therapeutic end points of radium-223. CONCLUSIONS: This study provides a first evidence that in real-life clinical practice, radium-223 therapy may induce skeletal fragility with high risk of VFs, likely by inhibition of bone formation and independently of ADT and abiraterone therapy.

Multimodality imaging of adult rhabdomyosarcoma: the added value of hybrid imaging.

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.