Rhabdomyosarcoma is the most common soft-tissue neoplasm in the pediatric population. The survival of children with rhabdomyosarcoma has only marginally improved over the past 25 years and remains poor for those with metastatic disease. A significant challenge to advances in treatment of rhabdomyosarcoma is the relative rarity of this disease, necessitating years to complete clinical trials. Progress can be accelerated by international cooperation and sharing national experiences. This necessitates agreement on a common language to describe patient cohorts and consensus standards to guide diagnosis, treatment, and response assessment. These goals formed the premise for creating the INternational Soft Tissue saRcoma ConsorTium (INSTRuCT) in 2017. Multidisciplinary members of this consortium have since developed international consensus statements on the diagnosis, treatment, and management of pediatric soft-tissue sarcomas. Herein, members of the INSTRuCT Diagnostic Imaging Working Group present international consensus recommendations for imaging of patients with rhabdomyosarcoma at diagnosis, at staging, and during and after completion of therapy. The intent is to promote a standardized imaging approach to pediatric patients with this malignancy to create more-reliable comparisons of results of clinical trials internationally, thereby accelerating progress in managing rhabdomyosarcoma and improving survival.

Fibrosarcoma (FS) is a malignant neoplasm of mesenchymal cells with no specific line of differentiation. Histologically, it mimics the wide spectrum of benign and malignant spindle cell neoplasms creating diagnostic conundrum. Immunohistochemistry plays a crucial role in the diagnosis which relies on various antibodies reacting with different antigens expressed by heterogeneous cells. Thus, there is a need to study the origin of the spindle cells to better comprehend their immunophenotypes that forms cornerstone for final confirmatory diagnosis. This case report describes the case of a 42-year-old male with soft-tissue mass in the mandible. Initial biopsy revealed it a reactive fibrous lesion; however, deeper biopsy confirmed spindle cell malignancy which exhibited immunonegativity to all other markers except vimentin. In addition, this case highlights the origin of various spindle cells with markers expressed during their development. The differential diagnosis of FS from other benign and malignant spindle cell lesions on the basis of clinical, histopathology, and immunohistochemistry is also elaborated.

BACKGROUND: This study aimed to develop a risk stratification model to differentiate benign and malignant MRI-imaged musculoskeletal soft-tissue tumours, informing decisions surrounding biopsy and follow-up imaging.
METHODS: Imaging of patients who underwent MRI and subsequent biopsy to evaluate a soft-tissue mass was retrospectively reviewed. Features analysed included patient age; tumour size; shape; margins; enhancement pattern; signal intensity pattern; deep fascia, neurovascular bundle, bone and joint involvement; and the presence of necrosis, haemorrhage, oedema and intralesional fat. Univariate comparisons, by final histopathological status, employed t-tests and chi-square tests, followed by simple and multiple logistic regressions. Variables included in the final multiple regression model were used to define a three-level risk stratification strategy.
RESULTS: One-hundred and ten patients were included in the analysis. Univariate relationships were identified between malignancy and age, tumour size, deep fascia involvement, neurovascular involvement, necrosis, haemorrhage, oedema and heterogeneous enhancement (all P < 0.01). Final multiple regression modelling included size, enhancement and oedema. Thirty of 40 (75%) tumours >5 cm with surrounding oedema (\'high risk\') were malignant, 13 of 47 (28%) tumours with one or more of tumour size >5 cm, surrounding oedema or heterogeneous enhancement (\'moderate risk\') were malignant, and none of the 16 tumours ≤5 cm with the absence of surrounding oedema and heterogeneous enhancement (\'low risk\') were malignant.
CONCLUSIONS: A model including tumour size, enhancement and oedema has potential to stratify soft-tissue tumours into high-, intermediate- and low-risk categories; this may inform decisions surrounding biopsy and follow-up imaging.

Soft-tissue hematomas are a common clinical entity often associated with trauma, surgery, and bleeding disorders. In the majority of cases, soft-tissue hematomas acutely appear and spontaneously resolve, but sometimes, they present as swellings that slowly expand and progressively increase with time. We present a case of a 70-year-old man with chronic expanding hematoma of the left flank without any history of recent trauma or other medical disease. The diagnosis could not be confirmed on imaging features alone, so the patient was taken to surgery for open biopsy and excision. In patients with slowly growing extremity masses without recent trauma or chronic medical disorders, the differential diagnosis becomes challenging, and chronic expanding hematoma should be considered in addition to soft-tissue sarcomas and other malignancies.

Soft-tissue lesions of the musculoskeletal system are commonly encountered in clinical practice and often manifest as palpable lesions. Moreover, the increasing use of cross-sectional imaging such as CT or MRI has resulted in the incidental detection of many soft-tissue lesions. Ultrasonography remains the primary imaging investigation for soft-tissue lesions. It has been shown to be helpful in depicting processes involving the soft-tissue lesions on cross-sectional imaging. This article describes the ultrasonographic findings of the most frequently incidentally detected benign and malignant soft-tissue lesions on cross-sectional imaging and suggests the characteristics of such diseases, focusing on the ultrasonographic features that allow accurate diagnosis. Familiarity with the clinical setting and the appearance of soft-tissue lesions on both ultrasonography and cross-sectional imaging can lead to accurate diagnosis and appropriate management of the condition.