Pediatric Osteosarcoma: Correlation of Imaging Findings with Histopathologic Features, Treatment, and Outcome

Neoplastic and Non-neoplastic Bone Lesions of the Knee

Numerous anatomical variants are described around the knee, many of which look like bony lesions, so it is important to know them to avoid unnecessary complementary tests and inadequate management. Likewise, several alterations in relation to normal development can also simulate bone lesions.However, numerous pathologic processes frequently affect the knee, including traumatic, inflammatory, infectious, and tumor pathology. Many of these entities show typical radiologic features that facilitate their diagnosis. In other cases, a correct differential diagnosis is necessary for proper clinical management.Despite the availability of increasingly advanced imaging techniques, plain radiography is still the technique of choice in the initial study of many of these pathologies. This article reviews the radiologic characteristics of tumor and nontumor lesions that may appear around the knee to make a correct diagnosis and avoid unnecessary complementary radiologic examinations and inadequate clinical management.

Unusual presentation of aneurysmal bone cyst (ABC) in children: pediatric intracranial osteosarcoma with secondary ABC

A 13-year-old female patient presented with painless vision loss and proptosis for 18 months. Imaging findings were highly suggestive of a supraorbital aneurysmal bone cyst (ABC) for which she underwent complete surgical excision. Postoperatively, she developed left hemiparesis. Computed tomography angiography (CTA) revealed right complete internal carotid arterial (ICA) thrombosis. This was managed conservatively, and she improved in hemiparesis over the next 3 weeks. Histopathology report revealed osteosarcoma with secondary ABC, for which she was referred for radiotherapy. At 1.5 months follow-up, the patient's left lower limb power improved to 4 + /5. She was walking without support, and her left upper limb power was 4/5.

Deep learning for differentiation of osteolytic osteosarcoma and giant cell tumor around the knee joint on radiographs: a multicenter study

OBJECTIVES

To develop a deep learning (DL) model for differentiating between osteolytic osteosarcoma (OS) and giant cell tumor (GCT) on radiographs.

METHODS

Patients with osteolytic OS and GCT proven by postoperative pathology were retrospectively recruited from four centers (center A, training and internal testing; centers B, C, and D, external testing). Sixteen radiologists with different experiences in musculoskeletal imaging diagnosis were divided into three groups and participated with or without the DL model's assistance. DL model was generated using EfficientNet-B6 architecture, and the clinical model was trained using clinical variables. The performance of various models was compared using McNemar's test.

RESULTS

Three hundred thirty-three patients were included (mean age, 27 years ± 12 [SD]; 186 men). Compared to the clinical model, the DL model achieved a higher area under the curve (AUC) in both the internal (0.97 vs. 0.77, p = 0.008) and external test set (0.97 vs. 0.64, p < 0.001). In the total test set (including the internal and external test sets), the DL model achieved higher accuracy than the junior expert committee (93.1% vs. 72.4%; p < 0.001) and was comparable to the intermediate and senior expert committee (93.1% vs. 88.8%, p = 0.25; 87.1%, p = 0.35). With DL model assistance, the accuracy of the junior expert committee was improved from 72.4% to 91.4% (p = 0.051).

CONCLUSION

The DL model accurately distinguished osteolytic OS and GCT with better performance than the junior radiologists, whose own diagnostic performances were significantly improved with the aid of the model, indicating the potential for the differential diagnosis of the two bone tumors on radiographs.

CRITICAL RELEVANCE STATEMENT

The deep learning model can accurately distinguish osteolytic osteosarcoma and giant cell tumor on radiographs, which may help radiologists improve the diagnostic accuracy of two types of tumors.

KEY POINTS

• The DL model shows robust performance in distinguishing osteolytic osteosarcoma and giant cell tumor. • The diagnosis performance of the DL model is better than junior radiologists'. • The DL model shows potential for differentiating osteolytic osteosarcoma and giant cell tumor.

Can conventional magnetic resonance imaging at presentation predict chemoresistance in osteosarcoma?

OBJECTIVES

Histological tumour necrosis is the current indicator for the response of osteosarcoma after neoadjuvant chemotherapy. Chemoresistant tumours require close monitoring and adjustment of treatment. Characteristics of tumours on baseline MRI may be able to predict response to chemotherapy. The aim is to identify which baseline MRI findings can help predict chemoresistant osteosarcoma.

METHODS

Baseline MRI before giving neoadjuvant chemotherapy of 95 patients during 2008-2021 was reviewed by 2 musculoskeletal radiologists. Histological necrosis from surgical specimens was the reference standard. MRIs were reviewed for tumour characteristics (tumour volume, maximum axial diameter, central necrosis, haemorrhage, fluid-fluid level), peritumoural bone and soft tissue oedema, and other parameters including intra-articular extension, epiphyseal involvement, neurovascular involvement, pathologic fracture, and skip metastasis. The cut-off thresholds were generated by receiver operating characteristic curves which then tested for diagnostic accuracy.

RESULTS

Two-third of patients were chemoresistance (histological necrosis <90%). Tumour volume >150 mL, maximum axial diameter >7.0 cm, area of necrosis >50%, presence of intra-articular extension, and peritumoural soft tissue oedema >6.5 cm significantly predicted chemoresistance, particularly when found in combination. Tumour volume >150 mL and maximum axial diameter >7.0 cm could be used as an independent predictor (multivariable analysis, P-value = .025, .045).

CONCLUSIONS

Findings on baseline MRI could help predicting chemoresistant osteosarcoma with tumour size being the strongest predictor.

ADVANCES IN KNOWLEDGE

Osteosarcomas with large size, large cross-sectional diameter, large area of necrosis, presence of intra-articular extension, and extensive peritumoural soft tissue oedema were most likely to have a poor response to neoadjuvant chemotherapy.

Imaging evaluation of blood supply changes after chemotherapy of osteosarcoma and its correlation with tumor necrosis rate

Background

Analysis of the tumour necrosis rate is an important method to evaluate the effect of neoadjuvant chemotherapy for osteosarcoma. However, at present, there is no specific imaging method to evaluate this effect. The purpose of this study was to evaluate the changes in blood supply after chemotherapy by measuring the CT enhancement rate and to analyse the correlation between the CT enhancement rate and the tumour necrosis rate.

Methods

Patients with primary osteosarcoma of the extremities treated in our institute from 2016 to 2017 were analysed retrospectively. In total, 103 eligible patients were enrolled in the study, including 67 males and 36 females, with an average age of 17.7 (6-54) years. Sixty cases had tumour sites in the femur, 25 in the tibia, 10 in the humerus, and eight in other sites. All patients received neoadjuvant chemotherapy including methotrexate, cisplatin + doxorubicin and ifosfamide before surgical treatment. All patients underwent enhanced CT examination of the same tumour site before and after the neoadjuvant chemotherapy protocol. The CT value before and after chemotherapy was measured and the enhancement rate was calculated. The change in the CT enhancement rate after chemotherapy was analysed. Changes in the CT enhancement rate were compared between patients with a tumour necrosis rate greater than 90% and those with one <90%.

Results

The average CT enhancement rates before and after chemotherapy were 1.68 (median 1.63, range 1.00-2.51) and 1.39 (median 1.28, range 1.00-2.83), respectively (P < 0.01). The average CT enhancement rate after chemotherapy decreased by 15.0% (median 16.7%, range -27.5-53%): 75 cases exhibited a decrease, three cases remained unchanged, and 25 cases exhibited an increase. The average enhancement rate before chemotherapy was 1.75 (median 1.68, range 1.18-2.51) in the group with a necrosis rate >90% and 1.62 (median 1.52, range 1.00-2.41) in the group with a necrosis rate < 90% (P = 0.068). The average CT enhancement rate after chemotherapy was 1.20 (median 1.21, range 1.00-1.53) in the group with a necrosis rate > 90% and 1.53 (median 1.43, range 1.00-2.83) in the group with a necrosis rate < 90% (P < 0.01). The enhancement rate of the group with a necrosis rate > 90% decreased by 29.0% (median 28%, range -2.3-53%) (P < 0.01); the enhancement rate of the group with a necrosis rate < 90% decreased by 3.8% on average (median 0.7%, range -27.5-44.5%) (P = 0.225).

Conclusion

After receiving neoadjuvant chemotherapy, most patients with osteosarcoma of the extremities exhibited reductions in the CT enhancement rate. In cases where the tumour necrosis rate was greater than 90%, the tumour blood supply was significantly reduced. This suggests that imaging evaluations based on the CT enhancement rate can be used as a reference for evaluating the preoperative effect of chemotherapy for osteosarcoma.

CT features of osteosarcoma lung metastasis: a retrospective study of 127 patients

Objective: Osteosarcoma lung metastases have a wide variety of CT presentations, representing a challenge for radiologists. Knowledge of atypical CT patterns of lung metastasis is important to differentiate it from benign lung disease and synchronous lung cancer, as well as to determine the extent of primary disease. The objective of this study was to analyze CT features of osteosarcoma lung metastasis before and during chemotherapy. Methods: Two radiologists independently reviewed chest CT images of 127 patients with histopathologically confirmed osteosarcoma treated between May 10, 2012 and November 13, 2020. The images were divided into two groups for analysis: images obtained before chemotherapy and images obtained during chemotherapy (initial CT examination). Results: Seventy-five patients were diagnosed with synchronous or metachronous lung metastases. The most common CT findings were nodules (in 95% of the patients), distributed bilaterally (in 86%), with no predominance regarding craniocaudal distribution (in 71%). Calcification was observed in 47%. Less common findings included intravascular lesions (in 16%), cavitation (in 7%), and the halo sign (in 5%). The primary tumor size was significantly greater (i.e., > 10 cm) in patients with lung metastasis. Conclusions: On CT scans, osteosarcoma lung metastases typically appear as bilateral solid nodules. However, they can have atypical presentations, with calcification being the most common. Knowledge of the typical and atypical CT features of osteosarcoma lung metastasis could play a key role in improving image interpretation in these cases.

PET/MR of pediatric bone tumors: what the radiologist needs to know

Integrated 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG) positron emission tomography (PET)/magnetic resonance (MR) imaging can provide "one stop" local tumor and whole-body staging in one session, thereby streamlining imaging evaluations and avoiding duplicate anesthesia in young children. 18F-FDG PET/MR scans have the benefit of lower radiation, superior soft tissue contrast, and increased patient convenience compared to 18F-FDG PET/computerized tomography scans. This article reviews the 18F-FDG PET/MR imaging technique, reporting requirements, and imaging characteristics of the most common pediatric bone tumors, including osteosarcoma, Ewing sarcoma, primary bone lymphoma, bone and bone marrow metastases, and Langerhans cell histiocytosis.

Case report and literature review: Primary leiomyosarcoma of the bone in the trochanteric region of the femur

Background

Primary leiomyosarcoma of the bone (LMSB) is an extremely rare, invasive, and highly destructive primary osteosarcoma with limited treatment options and poor prognosis. Only a few case reports of LMSB have been described because of its rarity. Therefore, clinicians have a limited understanding of its diagnosis, treatment, and prognosis, and the final diagnosis depends on histopathological findings. In this report, we describe a rare case of primary LMSB in the trochanteric region of the femur. Reporting this case may increase the dissemination and understanding of information regarding LMSB and provide a reference for the diagnosis and treatment of similar cases.

Case presentation

A 63-year-old woman presented with pain and limited movement of the left hip, which had lasted for 3 months, with no history of trauma or illness. Plain radiography and computed tomography revealed a solitary osteolytic lesion in the trochanteric area of the left femur with focal cortical destruction. Magnetic resonance imaging findings suggested invasion of the lesion into the bone cortex, forming a soft tissue mass, although no distant positive findings were observed on a whole-body bone scan. A bone tumor puncture biopsy was performed to obtain a final diagnosis, and histopathological evaluation revealed left femoral intertrochanteric leiomyosarcoma, classified as G1T2M0 and staged as IB (extracompartmental low-grade malignant) according to the Enneking staging system. Thus, we performed extensive debridement and left hip arthroplasty. Postoperative chemotherapy was administered, and the patient was followed up for 4 years. Four years later, the patient's left hip pain had resolved, joint activity was good, and no signs of recurrence or distant metastasis of the bone tumor were noted.

Conclusion

For proximal femoral Enneking stage IB LMSB, extensive tumor resection combined with tumor prosthesis replacement may be an effective treatment method to prolong the patient's lifespan and to restore joint function.