MRI Features as Prognostic Factors in Myxofibrosarcoma: Proposal of MRI Grading System

Role of magnetic resonance imaging in the prediction of histological grade in soft tissue sarcomas

BACKGROUND

Soft tissue sarcomas are rare malignant tumors with significant heterogeneity. The importance of classifying histological grades is fundamental to defining the treatment approach.

OBJECTIVE

To evaluate magnetic resonance imaging (MRI) in predicting the histological grade of soft tissue sarcomas.

METHODS

A retrospective observational study included patients over 18 years undergoing MRI and primary tumor surgery at AC Camargo Cancer Center from January 2015 to June 2022. Two radiologists evaluated MRI criteria (size, margin definition, heterogeneity of the T2 signal, high-intensity peritumoral signal on T2, and postperitumoral contrast), and a grading prediction score was calculated. χ2 and logistic regression analyses were conducted.

RESULTS

Sixty-eight patients were included (38 men; median: 48 years). Moreover, 52 high-grade and 16 low-grade tumors were observed. The MRI criteria associated with histological grade were peritumoral high-intensity T2-weighted signals (p < 0.001) and peritumoral postcontrast enhancement (p = 0.006). Logistic regression confirmed their significance (odds ratio [OR]: 11.8 and 8.8, respectively). Each score point increment doubled the chance of high-grade tumors (OR: 2.0; p = 0.014).

CONCLUSION

MRI effectively predicts histological grades of soft tissue sarcomas. Peritumoral high-intensity T2-weighted signals and peritumoral postcontrast enhancement are valuable indicators of high-grade tumors. This highlights MRI's importance in treatment decision-making for sarcoma patients.

Biology and Management of High-Grade Myxofibrosarcoma: State of the Art and Future Perspectives

Myxofibrosarcoma (MFS) is one of the most common adult soft tissue sarcomas, typically arising in the extremities. Histologically, MFS is classified into three grades: low, intermediate, and high. Histological grades correlate with distant metastases and tumor-associated mortality. The diagnosis of MFS is challenging due to a lack of well-characterized immunohistochemical markers. High-grade MFS displays highly complex karyotypes with multiple copy number alterations. Recent integrated genomic studies have shown the predominance of somatic copy number aberrations. However, the molecular pathogenesis of high-grade MFS remains poorly understood. The standard treatment for localized MFS is surgical resection. The systemic treatment options for advanced disease are limited. This review provides an updated overview of the clinical and imaging features, pathogenesis, histopathology, and treatment of high-grade MFS.

Fibroblastic and Myofibroblastic Soft-Tissue Tumors: Imaging Spectrum and Radiologic-Pathologic Correlation

Fibroblastic and myofibroblastic tumors are a variable group of neoplasms ranging from benign to malignant. These lesions may affect patients of any age group but are more frequently encountered in the pediatric population. Patient clinical presentation depends on the location, growth pattern, adjacent soft-tissue involvement, and pathologic behavior of these neoplasms. In the 2020 update to the World Health Organization (WHO) classification system, these tumors are classified on the basis of their distinct biologic behavior, histomorphologic characteristics, and molecular profiles into four tumor categories: (a) benign (eg, fibrous hamartoma of infancy, nodular fasciitis, proliferative fasciitis, fibroma of the tendon sheath, calcifying aponeurotic fibroma); (b) intermediate, locally aggressive (eg, desmoid fibromatosis); (c) intermediate, rarely metastasizing (eg, dermatofibrosarcoma protuberans, myxoinflammatory fibroblastic sarcoma, low-grade myofibroblastic sarcoma, infantile fibrosarcoma); and (d) malignant (eg, sclerosing epithelioid fibrosarcomas; low-grade fibromyxoid sarcoma; myxofibrosarcoma; fibrosarcoma, not otherwise specified). Detection of various components of solid tumors at imaging can help in prediction of the presence of corresponding histopathologic variations, thus influencing diagnosis, prognosis, and treatment planning. For example, lesions with a greater myxoid matrix or necrotic components tend to show higher signal intensity on T2-weighted MR images, whereas lesions with hypercellularity and dense internal collagen content display low signal intensity. In addition, understanding the radiologic-pathologic correlation of soft-tissue tumors can help to increase the accuracy of percutaneous biopsy and allow unnecessary interventions to be avoided. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Understanding a mass in the paraspinal region: an anatomical approach

The paraspinal region encompasses all tissues around the spine. The regional anatomy is complex and includes the paraspinal muscles, spinal nerves, sympathetic chains, Batson's venous plexus and a rich arterial network. A wide variety of pathologies can occur in the paraspinal region, originating either from paraspinal soft tissues or the vertebral column. The most common paraspinal benign neoplasms include lipomas, fibroblastic tumours and benign peripheral nerve sheath tumours. Tumour-like masses such as haematomas, extramedullary haematopoiesis or abscesses should be considered in patients with suggestive medical histories. Malignant neoplasms are less frequent than benign processes and include liposarcomas and undifferentiated sarcomas. Secondary and primary spinal tumours may present as midline expansile soft tissue masses invading the adjacent paraspinal region. Knowledge of the anatomy of the paraspinal region is of major importance since it allows understanding of the complex locoregional tumour spread that can occur via many adipose corridors, haematogenous pathways and direct contact. Paraspinal tumours can extend into other anatomical regions, such as the retroperitoneum, pleura, posterior mediastinum, intercostal space or extradural neural axis compartment. Imaging plays a crucial role in formulating a hypothesis regarding the aetiology of the mass and tumour staging, which informs preoperative planning. Understanding the complex relationship between the different elements and the imaging features of common paraspinal masses is fundamental to achieving a correct diagnosis and adequate patient management. This review gives an overview of the anatomy of the paraspinal region and describes imaging features of the main tumours and tumour-like lesions that occur in the region.

CT and MR Imaging of Retroperitoneal Sarcomas: A Practical Guide for the Radiologist

Primary retroperitoneal sarcomas (RPS) represent around 10-16% of all sarcomas, with liposarcomas and leiomyosarcomas being the most common subtypes. RPS have some peculiar characteristics, imaging appearances, worse prognosis, and complications compared to other locations of sarcoma. Commonly, RPS primarily present as large masses, progressively encasing adjacent structures, causing mass effect, and complications. RPS diagnosis is often challenging, and these tumors may be overlooked; however, failure to recognize RPS characteristics leads to a worse prognosis for the patients. Surgery is the only recognized curative treatment, but the anatomical constraints of the retroperitoneum limit the ability to achieve wide resection margins; therefore, these tumors have a high rate of recurrence, and require long-term follow-up. The radiologist has an important role in the diagnosis of RPS, the definition of their extent, and their follow-up. Specific knowledge of the main imaging findings is required to reach an early diagnosis, and, ultimately, to guarantee the best patient management. This article provides an overview of the current knowledge regarding cross-sectional imaging features of patients with retroperitoneal sarcomas, presenting tips and tricks to improve imaging diagnosis of RPS.

The Prognostic Relevance of MRI Characteristics in Myxofibrosarcoma Patients Treated with Neoadjuvant Radiotherapy

To improve local control, neoadjuvant radiotherapy (nRT) followed by surgery is the standard of care in myxofibrosarcoma (MFS) because of its infiltrative growth pattern. Nevertheless, local recurrence rates are high. Data on prognostic factors for poor clinical outcomes are lacking. This retrospective study thus investigates the prognostic relevance of magnetic resonance imaging (MRI) characteristics before and after nRT in 40 MFS patients, as well as their association with disease-free survival (DFS) and overall survival (OS). A vascular pedicle, defined as extra-tumoral vessels at the tumor periphery, was observed in 12 patients (30.0%) pre-nRT and remained present post-nRT in all cases. Patients with a vascular pedicle had worse DFS (HR 5.85; 95% CI 1.56-21.90; p = 0.009) and OS (HR 9.58; 95% CI 1.91-48.00; p = 0.006). An infiltrative growth pattern, referred to as a tail sign, was observed in 22 patients (55.0%) pre-nRT and in 19 patients (47.5%) post-nRT, and was associated with worse DFS post-nRT (HR 6.99; 95% CI 1.39-35.35; p = 0.019). The percentage of tumor necrosis estimated by MRI was increased post-nRT, but was not associated with survival outcomes. The presence of a tail sign or vascular pedicle on MRI could support the identification of patients at risk for poor clinical outcomes after nRT.

Imaging Recommendations for Diagnosis, Staging, and Management of Soft Tissue Sarcomas

Soft tissue lesions are a wide range of tumors of mesenchymal cell origin, occurring anywhere in the body with a vast number of histological subtypes both benign and malignant. These are common in clinical practice and vast majority are benign. This article focuses on soft tissue sarcoma of the trunk and extremities and discusses their imaging guidelines.

Soft-tissue sarcoma in adults: Imaging appearances, pitfalls and diagnostic algorithms

This article provides an overview of the current knowledge regarding diagnostic imaging of patients with soft-tissue sarcomas, which is a heterogeneous group of rare mesenchymal malignancies. After an initial contextualization, diagnostic flow-chart based on initial radiological findings of soft-tissue masses (with specific focus on adipocytic soft-tissue tumors [STTs], hemorragic STTs and retroperitoneal STTs) are provided considering relevant results from novel researches, guidelines, and experts' viewpoints, with the aim to help radiologists and clinicians in their practice. Particularly, the central place of sarcoma reference centers in the diagnostic and therapeutic management is highlighted, as well as the pivotal role that radiologists should play to correctly identify patients with soft-tissue sarcoma at the initial stage of the disease. Indications and methods for performing imaging-guided biopsies are also discussed, as well as clues to improve soft-tissue sarcoma grading with conventional and quantitative imaging.

Myxofibrosarcoma landscape: diagnostic pitfalls, clinical management and future perspectives

Myxofibrosarcoma (MFS) is a common entity of adult soft tissue sarcomas (STS) characterized by a predilection of the extremities and a high local recurrence rate. Originally classified as a myxoid variant of malignant fibrous histiocytoma, this musculoskeletal tumor has been recognized since 2002 as a distinct histotype showing a spectrum of malignant fibroblastic lesions with myxoid stroma, pleomorphism and curvilinear vessels. Currently, the molecular pathogenesis of MFS is still poorly understood and its genomic profile exhibits a complex karyotype with a number of aberrations including amplifications, deletions and loss of function. The diagnosis is challenging due to the unavailability of specific immunohistochemical markers and is based on the analysis of cytomorphologic features. The mainstay of treatment for localized disease is represented by surgical resection, with (neo)-adjuvant radio- and chemotherapy. In the metastatic setting, chemotherapy represents the backbone of treatments, however its role is still controversial and the outcome is very poor. Recent advent of genomic profiling, targeted therapies and larger enrollment of patients in translational and clinical studies, have improved the understanding of biological behavior and clinical outcome of such a disease. This review will provide an overview of current diagnostic pitfalls and clinical management of MFS. Finally, a look at future directions will be discussed.

Soft Tissue Sarcomas: The Role of Quantitative MRI in Treatment Response Evaluation

BACKGROUND

Although curative surgery remains the cornerstone of the therapeutic strategy in patients with soft tissue sarcomas (STS), neoadjuvant radiotherapy and chemotherapy (NART and NACT, respectively) are increasingly used to improve operability, surgical margins and patient outcome. The best imaging modality for locoregional assessment of STS is MRI but these tumors are mostly evaluated in a qualitative manner.

OBJECTIVE

After an overview of the current standard of care regarding treatment for patients with locally advanced STS, this review aims to summarize the principles and limitations of (i) the current methods used to evaluate response to neoadjuvant treatment in clinical practice and clinical trials in STS (RECIST 1.1 and modified Choi criteria), (ii) quantitative MRI sequences (i.e., diffusion weighted imaging and dynamic contrast enhanced MRI), and (iii) texture analyses and (delta-) radiomics.

Vascular Proximity Increases the Risk of Local Recurrence in Soft-Tissue Sarcomas of the Thigh-A Retrospective MRI Study

Simple Summary

Proximity to major vessels increases risk of local recurrence in soft tissue sarcomas of the thigh. When major vessels were observed to be surrounded by the tumor on preoperative MRI, vascular resection and by-pass reconstruction offered a better local control.

Abstract

The aim of this study was to establish the prognostic effects of the proximity of the tumor to the main vessels in patients affected by soft tissue sarcomas (STS) of the thigh. A total of 529 adult patients with deeply seated STS of the thigh and popliteal fossa were included. Vascular proximity was defined on MRI: type 1 > 5 mm; type 2 ≤ 5 mm and >0 mm; type 3 close to the tumor; type 4 enclosed by the tumor. Proximity to major vessels type 1–2 had a local recurrence (LR) rate lower than type 3–4 (p < 0.001). In type 4, vascular by-pass reduced LR risk. On multivariate analysis infiltrative histotypes, high FNLCC grade, radiotherapy administration, and type 3–4 of proximity to major vessels were found to be independent prognostic factors for LR. We observed an augmented risk of recurrence, but not of survival as the tumor was near to the major vessels. When major vessels were found to be surrounded by the tumor on preoperative MRI, vascular resection and bypass reconstruction offered a better local control.

Magnetic resonance imaging of soft tissue sarcoma: features related to prognosis

Magnetic Resonance Imaging is a fundamental tool in the evaluation of soft tissue sarcoma. Imaging features are relevant for the assessment of treatment strategies, surgical planning and also for patients' prognosis prediction. Among soft tissue sarcoma and also other malignancies, the size of the mass is usually considered the prognostic key element in diagnostic imaging. Moreover, several other features should be obtained from MRI studies with prognostic implications in all type of soft tissue sarcoma: peritumoral enhancement, signs of necrosis, deep location, ill-defined borders/signs of infiltrations. Focusing on soft tissue sarcoma subtypes, some other magnetic resonance imaging features are more specific and related to prognosis. In myxofibrosarcoma the magnetic resonance imaging "tail sign" and a "water-like" appearance on fluid-sensitive sequences, due to rich myxoid matrix content, are both associated with higher risk of local recurrence after surgical excision; nevertheless, the "tail sign" is also related to a higher risk of distant metastases at diagnosis. The "tail sign" is associated with higher risk of local recurrence after surgical excision in undifferentiated pleomorphic sarcoma as well. In patients affected by synovial sarcoma, the "triple sign" identifiable in magnetic resonance imaging (T2w sequences) is associated with decreased disease-free survival and indicates the simultaneous presence of solid cellular elements (intermediate signal intensity), hemorrhage or necrosis (high signal intensity) and fibrotic regions (low signal intensity). In addition, absence of calcifications are associated with reduced disease-free survival in patients affected by synovial sarcoma. Signal heterogeneity is associated with worst prognosis in all type of soft tissue sarcoma, particularly in myxoid liposarcoma. In recent years, several new quantitative tools applied on magnetic resonance imaging have been proved to predict patients' prognosis. Above all the new tools, radiomics seems to be one of the most promising, and, has been proved to have the capability in discriminating low-grade from high-grade soft tissue sarcomas. Therefore, magnetic resonance imaging studies in patients with soft tissue sarcoma should be accurately evaluated and their results should be taken into account for prognostic assessment.

Margin Assessment in Soft Tissue Sarcomas: Review of the Literature

Simple Summary

Many classifications to assess margins status for soft tissue sarcomas are reported in the literature. Most of the series are heterogeneous and variable in size, making it difficult to compare results from study to study. Thus, which is the best way to assess margins in order to predict the risk of local recurrence is still debated. The aim of this narrative review is to provide a comprehensive assessment of the literature on margins, and to highlight the need for a uniform description of the margin status for patients with soft tissue sarcomas (STS).

Abstract

Adequacy of margins must take into consideration both the resection margin width (quantity) and anatomic barrier (quality). There are several classification schemes for reporting surgical resection margin status for soft tissue sarcomas (STS). Most of the studies regarding treatment outcomes in STS included all histologic grades and histological subtypes, which include infiltrative and non-infiltrative subtypes and are very heterogeneous in terms of both histologic characteristics and treatment modalities (adjuvant treatments or not). This lack of consistency makes it difficult to compare results from study to study. Therefore, there is a great need for evidence-based standardization concerning the width of resection margins. The aim of this narrative review is to provide a comprehensive assessment of the literature on margins, and to highlight the need for a uniform description of the margin status for patients with STS. Patient cases should be discussed at multidisciplinary tumor boards and treatments should be individualized to clinical and demographic characteristics, which must include also a deep knowledge of specific histotypes behaviors, particularly infiltrative ones.

Development and validation of a prognostic nomogram for predicting the overall survival of myxofibrosarcoma patients: a large population-based study

Background

Although some studies have explored prognostic factors of myxofibrosarcoma (MFS), the sample sizes were small, generally fewer than 100 patients. There is still no effective prognostic model for MFS patients based on a large population and comprehensive factors. The present study was designed to establish and validate a large population-based, clinically relevant prognostic nomogram for predicting 3- and 5-year overall survival (OS) in patients with MFS.

Methods

We identified patients with MFS (ICD-O-3 code: 8811/3) who were diagnosed between 2004 and 2015 from the Surveillance, Epidemiology, and End Results database and separated them into training and validation cohorts (7:3 ratio). Survival was described using the Kaplan-Meier method. Univariate and multivariate Cox regression analyses were used to identify prognostic factors of survival. An individual nomogram was established to predict OS at 3 and 5 years in MFS patients. The discriminative ability and predictive accuracy of the nomogram were compared to those of the traditional American Joint Committee on Cancer (AJCC) staging system in the training and validation cohorts. Finally, MFS patients were divided into two subgroups based on the prognostic index (PI) score of the nomogram, and the survival outcomes of the subgroups were compared.

Results

A total of 1,270 patients were included. Age at diagnosis, total number of in situ or malignant tumors, tumor size, tumor site, tumor extension, AJCC stage, surgical status, chemotherapy, and radiotherapy were the independent predictors of survival and were included in the nomogram. The nomogram had C-indexes of 0.806 in the training cohort and 0.783 in the validation cohort, which were greater than those of the sixth edition of the AJCC staging system (training cohort, 0.669 and validation cohort, 0.674). Decision curve analysis (DCA) revealed that the nomogram was useful with high clinical net benefits. Survival outcomes were significantly different between the different risk subgroups (P<0.001).

Conclusions

A novel nomogram based on a large population was constructed to evaluate survival outcomes for MFS. Its predictive efficacy was markedly superior than that of the traditional sixth edition of the AJCC staging system.