Infarct-Associated Bone Sarcomas: Multimodality Imaging Findings

Role of hypercoagulability in multifocal osteonecrosis

Bone infarction describes bone marrow necrosis that occurs within a long bone's metaphysis or diaphysis. Multiple causative factors lead to ischaemia and subsequent necrosis of bone marrow. The role of hypercoagulability in bone ischaemia is a well-established phenomenon. Orthopaedic specialists play a crucial role in managing affected individuals due to their risk of developing malignancy. We had a case of a man in his late 20s with multifocal osteonecrosis. He was evaluated for hypercoagulability and was found to have mild hyperhomocysteinaemia. He also had an elevated level of factor VIII activity. He was managed conservatively and showed good improvement on vitamin supplementation for hyperhomocysteinaemia. As malignant transformation of the infarction can occur, orthopaedic surgeons need to be aware of this and keep such patients under regular follow-up.

Does the presence of macroscopic intralesional fat exclude malignancy? An analysis of 613 histologically proven malignant bone lesions

OBJECTIVE

To determine if macroscopic intralesional fat detected in bone lesions on CT by Hounsfield unit (HU) measurement and on MRI by macroscopic assessment excludes malignancy.

MATERIALS AND METHODS

All consecutive CT-guided core needle biopsies (CNB) of non-spinal bone lesions performed at a tertiary center between December 2005 and September 2021 were reviewed. Demographic and histopathology data were recorded. All cases with malignant histopathology were selected, and imaging studies were reviewed. Two independent readers performed CT HU measurements on all bone lesions using a circular region of interest (ROI) to quantitate intralesional fat density (mean HU < -30). MRI images were reviewed to qualitatively assess for macroscopic intralesional fat signal in a subset of patients. Inter-reader agreement was assessed with Cronbach's alpha and intraclass correlation coefficient.

RESULTS

In 613 patients (mean age 62.9 years (range 19-95 years), 47.6% female), CT scans from the CNB of 613 malignant bone lesions were reviewed, and 212 cases had additional MRI images. Only 3 cases (0.5%) demonstrated macroscopic intralesional fat on either CT or MRI. One case demonstrated macroscopic intralesional fat density on CT in a case of metastatic prostate cancer. Two cases demonstrated macroscopic intralesional fat signal on MRI in cases of chondrosarcoma and osteosarcoma. Inter-reader agreement was excellent (Cronbach's alpha, 0.95-0.98; intraclass correlation coefficient, 0.90-0.97).

CONCLUSION

Malignant lesions rarely contain macroscopic intralesional fat on CT or MRI. While CT is effective in detecting macroscopic intralesional fat in primarily lytic lesions, MRI may be better for the assessment of heterogenous and infiltrative lesions with mixed lytic and sclerotic components.

CLINICAL RELEVANCE STATEMENT

Macroscopic intralesional fat is rarely seen in malignant bone tumors and its presence can help to guide the diagnostic workup of bone lesions.

KEY POINTS

• Presence of macroscopic intralesional fat in bone lesions has been widely theorized as a sign of benignity, but there is limited supporting evidence in the literature. • CT and MRI are effective in evaluating for macroscopic intralesional fat in malignant bone lesions with excellent inter-reader agreement. • Macroscopic intralesional fat is rarely seen in malignant bone lesions.

Genomic Insights Into High-Grade Infarct-Associated Bone Sarcomas

Sarcomas rarely develop in bones previously compromised by infarcts. These infarct-associated sarcomas often present as undifferentiated pleomorphic sarcomas (UPS), and their genetic characteristics are poorly understood. High-grade UPS of bone are typically treated with a combination of surgery and chemotherapy, similar to osteosarcoma. We conducted a detailed clinicopathologic and genomic analysis of 6 cases of intraosseous sarcomas arising from histologically and radiographically confirmed bone infarcts. We analyzed 523 genes for sequence-level mutations using next-generation sequencing with the TruSight Oncology 500 panel and utilized whole-genome single nucleotide polymorphism Microarray (OncoScan CNV) to detect copy number alterations and loss of heterozygosity (LOH). Genomic instability was assessed through homologous recombination deficiency (HRD) metrics, incorporating LOH, telomeric allelic imbalance, and large-scale state transitions. Fluorescence in situ hybridization and immunohistochemistry validated the findings. The cohort included 3 men and 3 women, with a median age of 70 years, and tumors located in the femur and tibia. Five of the 6 patients developed distant metastases. Treatment involved surgery and chemotherapy or immune checkpoint inhibitors. Genomic analysis revealed significant complexity and high HRD scores, ranging from 32 to 57 (with a cutoff of 32). Chromosome 12 alterations, including segmental amplification or chromothripsis, were observed in 4 cases. Notably, MDM2 amplification, confirmed by fluorescence in situ hybridization, was detected in 2 cases. Homozygous deletion of CDKN2A/B was observed in all six cases. Tumor mutational burden levels ranged from 2.4 to 7.9 mutations per megabase. Notable pathogenic mutations included H3-3A mutations (p.G35R and p.G35W), and mutations in HRAS, DNMT3A, NF2, PIK3CA, POLE, and TP53, each in one case. These results suggest that high-grade infarct-associated sarcomas of bone, whereas sharing high levels of structural variations with osteosarcoma, may exhibit potentially less frequent TP53 mutations and more common CDKN2A/B deletions. This points to the possibility that the mutation spectrum and disrupted pathways could be distinct from conventional osteosarcoma.

ACR Appropriateness Criteria® Osteonecrosis: 2022 Update

Osteonecrosis is defined as bone death due to inadequate vascular supply. It is sometimes also called "avascular necrosis" and "aseptic necrosis" when involving epiphysis, or "bone infarct" when involving metadiaphysis. Common sites include femoral head, humeral head, tibial metadiaphysis, femoral metadiaphysis, scaphoid, lunate, and talus. Osteonecrosis is thought to be a common condition most commonly affecting adults in third to fifth decades of life. Risk factors for osteonecrosis are numerous and include trauma, corticosteroid therapy, alcohol use, HIV, lymphoma/leukemia, blood dyscrasias, chemotherapy, radiation therapy, Gaucher disease, and Caisson disease. Epiphyseal osteonecrosis can lead to subchondral fracture and secondary osteoarthritis whereas metadiaphyseal cases do not, likely explaining their lack of long-term sequelae. Early diagnosis of osteonecrosis is important: 1) to exclude other causes of patient's pain and 2) to allow for possible early surgical prevention to prevent articular collapse and need for joint replacements. Imaging is also important for preoperative planning. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Bone Infarcts and Tumorigenesis—Is There a Connection? A Mini-Mapping Review

(1) Background: Avascular necrosis (AVN) may affect every part of the bone. Epiphyseal infarcts are likely to be treated early because most are symptomatic. However, meta- and diaphyseal infarcts are silent and are diagnosed incidentally. Sarcomas developing in the necrotic bone are extremely rare, but they have been reported in the literature. (2) Methods: We conducted a mapping review of recent evidence regarding these malignancies. Methods: A mapping review using a systematic search strategy was conducted to answer research questions. We limited our research to the last ten years (2012–2022). (3) Results: A total of 11 papers were identified, including 9 case reports and 3 case series. The pathomechanism of carcinogenesis in AVN was not investigated to date. Histologically, most tumors were malignant fibrous histiocytoma. The prognosis is relatively poor, especially for patients with metastases, but adjuvant chemotherapy may increase short- and long-term survival. (4) Conclusions: Since AVN-related malignancies are sporadic, no prospective studies have been conducted. The majority of evidence comes from small case series. More research is needed to identify the risk factors that would justify follow-up of patients after bone infarcts at higher risk of developing a malignancy.

Sclerotic bone lesions caused by non-infectious and non-neoplastic diseases: a review of the imaging and clinicopathologic findings

Bone sclerosis is a focal, multifocal, or diffuse increase in the density of the bone matrix on radiographs or computed tomography (CT) imaging. This radiological finding can be caused by a broad spectrum of diseases, such as congenital and developmental disorders, depositional disorders, and metabolic diseases. The differential diagnosis can be effectively narrowed by an astute radiologist in the light of the clinical picture and typical findings on imaging. Some of these lesions are rare and have been described as case reports and series in the literature. This article aims to collate the clinical-radiologic findings of non-infectious and non-neoplastic causes of bone sclerosis with relevant imaging illustrations.

Pearls and Pitfalls for Soft-Tissue and Bone Biopsies: A Cross-Institutional Review

Management of soft-tissue and bone neoplasms depends on a definitive histologic diagnosis. Percutaneous image-guided biopsy of bone and soft-tissue tumors is a cost-effective and accurate method to obtain a histopathologic diagnosis. Biopsy requests must be approached thoughtfully to avoid numerous potential pitfalls. Hasty biopsy planning places the patient at increased risk for misdiagnosis, delayed therapy, repeated invasive procedures, and substantial morbidity. Biopsy planning begins with a thorough review of the relevant clinical history and pertinent imaging. The biopsy route must be planned in concert with the referring orthopedic oncologist to preserve limb-sparing options. Carefully selecting the most appropriate imaging modality to guide the biopsy increases the chances of reaching a definitive diagnosis. It is also critical to identify and target with expertise the part of the lesion that is most likely to yield an accurate diagnosis. Percutaneous biopsy is a safe procedure, and familiarity with preprocedural laboratory testing parameters, anticoagulation guidelines, and commonly used sedation medications minimizes the risk of complications while ensuring patient comfort. Nondiagnostic biopsy results are not infrequent and may still have value in guiding patient treatment. Awareness of the imaging manifestations of tumor recurrence is also important. The aim of this article is to provide a comprehensive review of pertinent preprocedural, periprocedural, and postprocedural considerations for bone and soft-tissue musculoskeletal biopsies.The online slide presentation from the RSNA Annual Meeting is available for this article.^©RSNA, 2020.

Undifferentiated Pleomorphic Sarcoma Arising in a Fibrous Dysplasia Confirmed by GNAS Mutation Analysis: A Case Report

CASE

We report the case of a 78-year-old woman with undifferentiated pleomorphic sarcoma (UPS) of the proximal femur arising in a previous site of fibrous dysplasia (i.e., a liposclerosing myxofibrous tumor) that had been treated 4 years earlier with curetted surgery. GNAS mutation was detected in both the previous benign lesion and the UPS.

CONCLUSION

Genetic analysis is useful in demonstrating the origin of the tumor especially in fibrous dysplasia with severe degeneration that have undergone malignant transformation.

Untreated plasmacytoma of bone containing macroscopic intralesional fat and mimicking intraosseous lipoma: A case report and review of the literature

Solitary plasmacytoma is a rare form of plasma cell neoplasm defined by local neoplastic accumulation of monoclonal plasma cells in the absence of systemic proliferative plasma cell disease. In this case report, a 65-year-old female with remote past medical history of papillary thyroid cancer presented with shoulder pain and radiographs showing an aggressive osteolytic lesion presumed to represent an osseous metastasis. The subsequent MRI and CT examinations demonstrated diffuse intralesional macroscopic fat without a nonlipogenic soft tissue component or focal, nodular mass-like enhancement. The presence of macroscopic fat in an untreated osseous lesion suggested a benign lesion with the favored diagnosis an intraosseous lipoma with non-displaced pathological fracture. Therefore, the decision was made to forego image-guided percutaneous biopsy and instead proceed directly to open surgical biopsy and partial distal claviculectomy. Pathology of the resected specimen showed focally dense infiltration of plasma cells within the marrow space and scant hematopoiesis compatible with a plasma cell neoplasm. To the best of our knowledge, this is first case report of solitary plasmacytoma of bone, or any untreated plasma cell neoplasm, containing macroscopic fat upon imaging. The decision to forego image-guided percutaneous biopsy had significant treatment implications as the primary therapy for patients with SPB is not surgical, but localized radiation therapy. Based on this case, solitary plasmacytoma of bone may be included as one of the rare fat containing malignant bone lesions and imaging guided percutaneous biopsy should be considered in symptomatic fat-containing bone lesions.

A Rare Case of an Osteolytic Bone-infarct-associated Osteosarcoma: Case Report with Radiographic and Histopathologic Correlation, and Literature Review

Benign lesions such as Paget’s disease of the bone, enchondroma, osteochondromas, chronic osteomyelitis/infections and bone infarcts may rarely undergo malignant degeneration/transformation into sarcomas. To date, only 14 prior bone infarct-associated osteosarcomas have been described, with just two being primarily osteolytic. We discuss a case of a patient with a humeral bone-infarct, who presented with a presumed benign pathological fracture of the humerus through the bone infarct. Subsequent imaging and biopsy showed that there was a malignant degeneration into a primarily osteolytic osteosarcoma. We review the patient’s presentation, radiographic and histologic appearance of the osteosarcoma and discuss the epidemiology, surgical and non-surgical treatment and surveillance of bone-infarct-associated osteosarcomas.

Conditions Simulating Primary Bone Neoplasms

A number of nonneoplastic conditions can mimic tumors of bone. Some of the more common mimics of primary bone tumors include infectious, inflammatory, periosteal, and degenerative joint disease-associated lesions that produce tumorlike bone surface-based or intraosseous lesions. This article considers a spectrum of reactive and nonreactive processes including stress fracture, subchondral cysts, osteonecrosis, heterotopic ossification, osteomyelitis, sarcoidosis, and amyloidoma that can present in such a way that they are mistaken for a tumor arising primary in bone.

Myxofibrosarcoma: First report of myxofibrosarcoma of bone arising at a bone infarct

Approximately 3300 new primary bone tumors will present to American physicians this year. This small but important group of malignancies has become more defined with developments in pathologic morphology, immunohistochemistry, and molecular studies. As tumor types are better partitioned, their specific characteristics are more readily observed. In this article we present the first reported case of a myxofibrosarcoma of bone developing within a bone infarct. With improved delineation of rarer tumor types, it is expected that additional cases of myxofibrosarcoma of bone will be recognized, potentially arising from a bone infarct. By framing the context, describing the case, and sharing pertinent figures, we hope to facilitate this recognition.