Soft tissue tumor imaging in adults: whole-body staging in sarcoma, non-malignant entities requiring special algorithms, pitfalls and special imaging aspects. Guidelines 2024 from the European Society of Musculoskeletal Radiology (ESSR).

OBJECTIVES: The revised European Society of Musculoskeletal Radiology (ESSR) consensus guidelines on soft tissue tumor imaging represent an update of 2015 after technical advancements, further insights into specific entities, and revised World Health Organization (2020) and AJCC (2017) classifications. This second of three papers covers algorithms once histology is confirmed: (1) standardized whole-body staging, (2) special algorithms for non-malignant entities, and (3) multiplicity, genetic tumor syndromes, and pitfalls. MATERIALS AND METHODS: A validated Delphi method based on peer-reviewed literature was used to derive consensus among a panel of 46 specialized musculoskeletal radiologists from 12 European countries. Statements that had undergone interdisciplinary revision were scored online by the level of agreement (0 to 10) during two iterative rounds, that could result in 'group consensus', 'group agreement', or 'lack of agreement'. RESULTS: The three sections contain 24 statements with comments. Group consensus was reached in 95.8% and group agreement in 4.2%. For whole-body staging, pulmonary MDCT should be performed in all high-grade sarcomas. Whole-body MRI is preferred for staging bone metastasis, with [18F]FDG-PET/CT as an alternative modality in PET-avid tumors. Patients with alveolar soft part sarcoma, clear cell sarcoma, and angiosarcoma should be screened for brain metastases. Special algorithms are recommended for entities such as rhabdomyosarcoma, extraskeletal Ewing sarcoma, myxoid liposarcoma, and neurofibromatosis type 1 associated malignant peripheral nerve sheath tumors. Satisfaction of search should be avoided in potential multiplicity. CONCLUSION: Standardized whole-body staging includes pulmonary MDCT in all high-grade sarcomas; entity-dependent modifications and specific algorithms are recommended for sarcomas and non-malignant soft tissue tumors. CLINICAL RELEVANCE STATEMENT: These updated ESSR soft tissue tumor imaging guidelines aim to provide support in decision-making, helping to avoid common pitfalls, by providing general and entity-specific algorithms, techniques, and reporting recommendations for whole-body staging in sarcoma and non-malignant soft tissue tumors. KEY POINTS: An early, accurate, diagnosis is crucial for the prognosis of patients with soft tissue tumors. These updated guidelines provide best practice expert consensus for standardized imaging algorithms, techniques, and reporting. Standardization can improve the comparability examinations and provide databases for large data analysis.

Magnetic resonance imaging characteristics of musculoskeletal hydatid disease.

BACKGROUND: Hydatid disease is a parasitic infection seen in endemic areas. Musculoskeletal hydatid disease is rarely reported. PURPOSE: To describe the magnetic resonance imaging (MRI) features of musculoskeletal hydatid disease and to highlight the specific findings in the diagnosis of hydatid cysts. MATERIAL AND METHODS: The MRI scans of 29 cases diagnosed as musculoskeletal hydatid disease between 2000 and 2022 were retrospectively analyzed. The localization, size, appearance (unilocular or multilocular), signal characteristics, rim sign, presence of internal septa and membrane, and gadolinium enhancement pattern of hydatid cysts were evaluated. RESULTS: A total of 29 patients diagnosed with hydatid cyst were included in the study. Of the lesions, 18 were localized in bone and 11 were in soft tissue. The bone hydatid cysts on MRI showed heterogeneous low to intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images in the medullary bone. In 15/18 patients, there was also cortical destruction and extension into the adjacent soft tissue planes. In 8/11 cases where the cyst was located in muscle tissue, the "cyst or cysts within a cyst" appearance was observed on MRI. The rim sign was observed in 7/11 cases and the "water lily" sign was noted in 2/11 cases. CONCLUSION: MRI provides valuable information for the diagnosis of hydatid disease with its distinctive imaging features. Knowledge of the different patterns of hydatid cysts on MRI may be helpful in the diagnosis of this disease.

Soft tissue tumor imaging in adults: European Society of Musculoskeletal Radiology-Guidelines 2023-overview, and primary local imaging: how and where?

OBJECTIVES: Early, accurate diagnosis is crucial for the prognosis of patients with soft tissue sarcomas. To this end, standardization of imaging algorithms, technical requirements, and reporting is therefore a prerequisite. Since the first European Society of Musculoskeletal Radiology (ESSR) consensus in 2015, technical achievements, further insights into specific entities, and the revised WHO-classification (2020) and AJCC staging system (2017) made an update necessary. The guidelines are intended to support radiologists in their decision-making and contribute to interdisciplinary tumor board discussions. MATERIALS AND METHODS: A validated Delphi method based on peer-reviewed literature was used to derive consensus among a panel of 46 specialized musculoskeletal radiologists from 12 European countries. Statements were scored online by level of agreement (0 to 10) during two iterative rounds. Either "group consensus," "group agreement," or "lack of agreement" was achieved. RESULTS: Eight sections were defined that finally contained 145 statements with comments. Overall, group consensus was reached in 95.9%, and group agreement in 4.1%. This communication contains the first part consisting of the imaging algorithm for suspected soft tissue tumors, methods for local imaging, and the role of tumor centers. CONCLUSION: Ultrasound represents the initial triage imaging modality for accessible and small tumors. MRI is the modality of choice for the characterization and local staging of most soft tissue tumors. CT is indicated in special situations. In suspicious or likely malignant tumors, a specialist tumor center should be contacted for referral or teleradiologic second opinion. This should be done before performing a biopsy, without exception. CLINICAL RELEVANCE: The updated ESSR soft tissue tumor imaging guidelines aim to provide best practice expert consensus for standardized imaging, to support radiologists in their decision-making, and to improve examination comparability both in individual patients and in future studies on individualized strategies. KEY POINTS: • Ultrasound remains the best initial triage imaging modality for accessible and small suspected soft tissue tumors. • MRI is the modality of choice for the characterization and local staging of soft tissue tumors in most cases; CT is indicated in special situations. Suspicious or likely malignant tumors should undergo biopsy. • In patients with large, indeterminate or suspicious tumors, a tumor reference center should be contacted for referral or teleradiologic second opinion; this must be done before a biopsy.

Tumor-like Lesions of Bone and Soft Tissues and Imaging Tips for Differential Diagnosis.

In the musculoskeletal system, tumor-like lesions may present similar imaging findings as bone and soft tissue tumors and can be defined as tumors on radiologic examinations. Misinterpretation of the imaging findings can lead to inappropriate clinical management of the patient.There is still some debate regarding the pathophysiology and origin of tumor-like lesions that include congenital, developmental, inflammatory, infectious, metabolic, reactive, posttraumatic, post-therapeutic changes, and some miscellaneous entities causing structural changes. Although tumor-like lesions are historically defined as non-neoplastic lesions, some of them are classified as real neoplasms.We discuss a spectrum of entities mimicking tumors of bone and soft tissues that include various non-neoplastic diseases and anatomical variants based on imaging findings.

The value of magnetic resonance arthrography in the evaluation of repaired menisci.

AIM: To evaluate the diagnostic value of direct magnetic resonance (MR) arthrography in detection of re-torn or unhealed menisci which were previously repaired. MATERIALS AND METHODS: Twenty-six menisci of 24 symptomatic patients who had undergone a meniscus repair surgery were included in this retrospective study. These patients had been evaluated with gadolinium-enhanced direct MR arthrography. A subsequent second-look arthroscopy was performed thereafter. The findings of MR arthrography were compared with the arthroscopic findings. RESULTS: Sixteen recurrent meniscal lesions were detected with MR arthrography; the remaining ten repaired menisci were evaluated as healed. At second-look arthroscopy, six out of 26 repaired menisci were evaluated as completely healed. Eight of them had incomplete healing, and 12 of them were unhealed. MR arthrography had four false-negative results, but there were none false-positive results. It was arthroscopically shown that three of these four false-negative results were belonged to patients who had incomplete healing. MR arthrography had a sensitivity, specificity, and overall accuracy of 80, 100, and 84.6 %, respectively. When incomplete lesions were left out of analysis, its sensitivity and accuracy reached to 94.8 and 94.4 %. CONCLUSION: The findings of this study showed that MR arthrography was a reliable diagnostic tool in evaluating previously repaired menisci. Yet diagnosis of incomplete meniscal lesions seemed to be challenging.

Pitfalls in MR imaging of musculoskeletal tumors.

A wide range of musculoskeletal tumors and tumor-like conditions may be encountered when patients undergo radiologic examinations. Although MR imaging is a powerful medical imaging method that has been used extensively in the evaluation of musculoskeletal tumors, nontumoral or tumorlike lesions may have similar imaging findings. The imaging features of certain normal, reactive, benign neoplastic, inflammatory, traumatic, or degenerative processes in the musculoskeletal system may mimic malignant tumors. Misinterpretation of the imaging findings can lead to inappropriate clinical management of the patient. We review and describe the MR imaging characteristics of nontumoral bone lesions that are located in the marrow cavity, cortical bone, or in both, and soft tissue lesions that may be misinterpreted as sarcoma.

Primary tumors of the spine.

Spinal tumors consist of a large spectrum of various histologic entities. Multiple spinal lesions frequently represent known metastatic disease or lymphoproliferative disease. In solitary lesions primary neoplasms of the spine should be considered. Primary spinal tumors may arise from the spinal cord, the surrounding leptomeninges, or the extradural soft tissues and bony structures. A wide variety of benign neoplasms can involve the spine including enostosis, osteoid osteoma, osteoblastoma, aneurysmal bone cyst, giant cell tumor, and osteochondroma. Common malignant primary neoplasms are chordoma, chondrosarcoma, Ewing sarcoma or primitive neuroectodermal tumor, and osteosarcoma. Although plain radiographs may be useful to characterize some spinal lesions, magnetic resonance imaging is indispensable to determine the extension and the relationship with the spinal canal and nerve roots, and thus determine the plan of management. In this article we review the characteristic imaging features of extradural spinal lesions.

Musculoskeletal brucellosis.

Brucellosis is a zoonosis of worldwide distribution caused by small gram-negative nonencapsulated coccobacilli of the genus Brucella. It is characterized by a granulomatous reaction in the reticuloendothelial system. Because it affects several organs and tissues, it may have various clinical manifestations. Musculoskeletal involvement is one of the most common locations, and the frequency of bone and joint (osteoarticular) involvement of brucellosis varies between 10% and 85%. Osteoarticular involvement includes spondylitis, sacroiliitis, osteomyelitis, peripheral arthritis, bursitis, and tenosynovitis. The most common osteoarticular finding in children is monoarticular arthritis, mostly located in the knees and hips; whereas in adults, sacroiliitis is the most frequent. Imaging studies, including radiography, computed tomography (CT), magnetic resonance (MR) imaging, and bone scintigraphy, have been used for diagnosis. Radiography is limited to evaluating the focal form of spinal brucellosis and advanced disease at the joints. CT and bone scintigraphy have limited value because of their inadequate soft tissue resolution. MR imaging is the method of choice to assess the extent of disease and follow up the treatment response. However, MR imaging has a low specificity to predict the exact cause of an osteoarticular lesion, and in case of arthralgia or symptoms of osteomyelitis or spondylodiscitis, the index of suspicion should be high in regions where the disease is endemic.

Musculoskeletal hydatid disease.

Hydatid disease is an infectious disease caused by the larval stage of the parasitic tapeworm Echinococcosis granulosus. Its distribution is worldwide. Although hydatid disease can develop in almost any part of the body, it is most commonly found in the liver and lung. Musculoskeletal involvement is rare. The radiological appearance of the hydatid disease of musculoskeletal system mimics tumors and other inflammatory conditions. Therefore preoperative diagnosis of musculoskeletal hydatid disease is sometimes difficult clinically and radiologically. On radiography, different radiographic changes may occur. In cases of osteolytic and inflammatory changes, it may mimic any variant of nonspecific or specific osteomyelitis. Bone erosion and destruction may lead to almost complete osteolysis, bone may distort, and on occasion, its radiologic appearances may be confused with those of a malignant bone tumor. Computed tomography (CT) is more accurate in delineating the area of destruction. The primary role of CT and magnetic resonance imaging is in the recognition of extraosseous spread of the hydatid disease within the soft tissues. This article reviews the pathological basis and the clinical and imaging features of musculoskeletal hydatid disease.

Solitary osteochondroma causing popliteal pseudoaneurysm that presented as a mass lesion.

Osteochondromas are the most frequently occurring bone tumors and can rarely lead to vascular complications. A 14-year-old boy with solitary exostosis of the right femur presented with a mass lesion at the posterior aspect of the thigh. Radiological studies demonstrated a popliteal artery pseudoaneurysm. In this case report, radiological findings of this lesion are reviewed.