Bone lesions are more frequently detected with the increasing number of radiological examinations. However, the diagnosis of bone lesions can be difficult due to the broad spectrum of differential diagnoses and overlapping imaging features [1–5,10]. Focal bone lesions may be related to benign or malignant tumors, metabolic or infectious disorders, degenerative changes, and tumor-like conditions [4,5,10,20]. Thus, an accurate differentiation between benign and potentially malignant lesions is crucial to avoid underestimation of disease or overtreatment of benign lesions and to address critical aspects of patient management, such as determining if the lesion can be monitored over time or if the patient should be referred to a specialized oncology center [1,19].

There is a need for multidisciplinary communication on bone lesions, and consensus regarding systematic and standardized approaches for bone lesion evaluation is desirable [1,19]. The clinical presentations of bone tumors are usually nonspecific, such as pain, discomfort, and palpable mass [5,8]. Radiologists, pathologists, and clinicians should collaborate to reach an accurate diagnosis for appropriate treatment selection [2,5,20].

Following the success of the Breast Imaging Reporting and Data System (BI-RADS), a series of RADS classification systems have been proposed, including systems for colon, liver, lung, head and neck, ovarian-adnexal, prostate, and thyroid imaging [1]. RADS systems facilitate structured reporting and standardized communication, thereby enhancing collaboration among healthcare professionals from different specialties [1,19]. Currently, several RADS classifications for bone lesions have been proposed. The Radiological Evaluation Score for Bone Tumors (REST) on radiography was developed using cohorts of patients with primary bone tumors. Subsequently, Bone-RADS on radiography for tumor risk stratification and management was established through expert consensus by the Committee of the American College of Radiology (ACR) [1].

The Bone Tumor Imaging Reporting and Data System (BTI-RADS) was later developed using histologically confirmed bone tumors, although it required both CT and MRI evaluation [3,10]. The Society of Skeletal Radiology (SSR) Bone-RADS system for CT and MRI includes four diagnostic algorithms for CT lucent lesions, CT sclerotic/mixed lesions, MRI T1 hyperintense lesions, and MRI T1 hypointense lesions, respectively [1]. Bone-RADS is presented in a decision-tree approach to simplify interpretation and management recommendations, primarily relying on lesion imaging characteristics [1,3].

MRI evaluation of bone tumors remains challenging because of overlapping appearances between benign, indeterminate, and aggressive lesions [2,3,11,18]. Bone-RADS provides a standardized scoring system that helps classify lesions as benign, indeterminate, or aggressive based on imaging morphology, signal characteristics, enhancement patterns, and ancillary imaging features [1,3,19]. Such a structured approach may improve diagnostic confidence, reduce variability in reporting, and guide appropriate patient management [1,18,19].

OBJECTIVES

• To demonstrate Bone-RADS application in MRI.
• To present a pictorial case series.
• To highlight the role of Bone-RADS in guiding management decisions.

MATERIALS & METHODS

• Study design: Retrospective descriptive study.
• Place of study: Department of Radiodiagnosis, BIMS Belagavi.
• Sample size: 20 MRI-evaluated bone lesions (March to July).
• Categorized using MRI ACR BONE-RADS classification.
• Classification was based on signal characteristics, morphology, enhancement pattern, and ancillary imaging features.

Table 1: ACR Bone-RADS Classification Categories, Imaging Interpretation, and Recommended Management

Table 2: Demographic Profile, Bone-RADS Classification and diagnosis of Bone Lesions Evaluated on MRI.

PICTORIAL PRESENTATION OF CASES

BONE RADS 1

Total 5 cases of bone rads 1 were there out of which 2 cases are shown below as representation images.

Case 1:

A 12 year old male patient with complaints of pain in the knee, ccoronal MRI images demonstrating a well-defined eccentric cortically based metaphyseal lesion in the proximal tibia, showing a narrow zone of transition and lobulated margins. The lesion appears isointense on T1-weighted images with peripheral T2 hypointense sclerosis and no associated cortical breach, periosteal reaction, soft tissue component, or surrounding marrow edema (arrows). Imaging findings are characteristic of non-ossifying fibroma (NOF), a benign fibrous cortical lesion, categorized as Bone-RADS 1.

Case 2:

A 16 year old male patient Coronal T1-weighted and fluid-sensitive sequences show well-defined exophytic osseous lesions with continuity of the cortex and medullary cavity with the parent bone. The lesiondemonstrate a cartilage cap appearing hyperintense on T2-weighted images. No associated cortical destruction, marrow edema, soft tissue mass, or aggressive periosteal reaction is seen. Imaging features are characteristic of benign osteochondroma (Bone-RADS 1)

BONE RADS 2

CASE 3:

Coronal MRI and CT images demonstrating a well-defined expansile intramedullary cystic lesion involving the proximal humeral shaft (arrows). The lesion shows fluid signal intensity with cortical thinning and mild osseous expansion without cortical destruction, aggressive periosteal reaction, or soft tissue component. CT image demonstrates a dependent cortical fragment within the cystic cavity (star), representing the classic “fallen fragment sign,” characteristic of a simple bone cyst. Imaging findings are consistent with simple bone cyst (SBC) (Bone-RADS 2).

CASE 4 :

MRI images of the talus in a 27-year-old male demonstrating a multiloculated expansile lesion consistent with aneurysmal bone cyst. The lesion appears hyperintense on (a) T1-weighted images (block arrow) and markedly hyperintense on (b) T2-weighted images with internal fluid-fluid levels/T2 shading (open arrow). Associated cortical expansion and thinning are noted without significant soft tissue component. Imaging findings are characteristic of aneurysmal bone cyst (ABC) (Bone-RADS 2).

CASE 5 : MRI images of the proximal tibia in a 26-year-old female demonstrating a well-defined eccentric metaphyseal lesion consistent with chondromyxoid fibroma. The lesion appears iso- to hypointense on (a) T1-weighted images (open arrow) and markedly hyperintense on (b) T2-weighted images (block arrow), with associated cortical thinning and mild expansile remodelling. No aggressive periosteal reaction or soft tissue component is identified. Imaging findings are characteristic of chondromyxoid fibroma.

BONE RADS 3

CASE 6:Coronal MRI images of 21year old male patient demonstrating a well-defined expansile intramedullary lesion involving the proximal femur. The lesion appears isointense on T1-weighted images and heterogeneously enhancing on T1 post contrast images s with cortical thinning and mild osseous expansion. No cortical destruction, periosteal reaction, or associated soft tissue component is identified. Imaging findings are consistent with fibrous dysplasia. BONE RADS 3.

CASE 7: RI images of the involved bone in a 32-year-old male demonstrating fibrous dysplasia with secondary cystic changes. Coronal T2-weighted and T1-weighted images show hyperintense cystic components on T2-weighted imaging with corresponding hypo intensity on T1-weighted images. Associated T1/T2 hypointense sclerotic areas are also noted. Mild expansile remodelling is present without cortical destruction or soft tissue extension. Imaging findings are consistent with fibrous dysplasia with secondary cystic degeneration. BONE RADS 3.

BONE RADS 4

CASE 8 : MRI images of the right distal femur in a 9-year-old female demonstrating features of osteosarcoma.Coronal T2-weighted and T1-weighted images show a heterogeneous intramedullary lesion with predominantly T2/T1 hypointense matrix mineralization (open and block arrows) and associated aggressive periosteal elevation (long arrow). T1-weighted images also demonstrate hypointense tumor extension across the physis into the epiphysis (notched arrow).  Post-contrast T1-weighted fat-suppressed image reveals central non-enhancing hypointense necrotic/calcified areas with peripheral heterogeneous enhancement (notched arrow). Imaging findings are consistent with conventional osteosarcoma.  Diagnosis was confirmed on biopsy.

CASE 9 : Multiple myeloma involving the left clavicle in a 48-year-old female patient demonstrates a lobulated marrow-replacing expansile lesion centred within the left clavicle. On MRI, the lesion appears isointense to skeletal muscle on T1-weighted images and heterogeneously hyperintense on T2-weighted images, reflecting high cellularity and increased water content. There is associated cortical destruction with extension into the adjacent soft tissues, indicating aggressive osseous involvement. The lesion exhibits aggressive features, including medullary expansion, cortical breach, and extraosseous soft tissue component. On biopsy it was confirmed as multiple myeloma.

CASE 10 : Giant cell tumour involving the left acetabulum in a 50-year-old male patient demonstrates an expansile osteolytic lesion centred in the periacetabular region with aggressive imaging characteristics. On MRI, the lesion appears heterogeneously hyperintense on T2-weighted imagesand shows avid post-contrast enhancement on T1-weighted contrast-enhanced sequences, reflecting its hypervascular solid nature. There is associated cortical destruction with extension into the adjacent soft tissues, indicative of locally aggressive behaviour. Giant cell tumours typically occur in skeletally mature individuals and characteristically demonstrate expansile eccentric lytic morphology with cortical thinning or breach. MRI is valuable in delineating marrow involvement, articular extension, cortical integrity, and extraosseous soft tissue components BONERADS 4. On biopsy the lesion was found to be giant cell tumour.

Figures a-c: Graphical representation of demographic and lesion distribution in the study population, demonstrating male predominance, majority of cases in younger age groups, and predominance of benign bone lesions over indeterminate and aggressive lesions.

RESULTS

A total of 20 bone lesions were evaluated using the ACR Bone-RADS classification system on MRI. The demographic analysis demonstrated a male predominance, accounting for 67% of cases, while females constituted 33% of the study population. The age distribution ranged from the first to sixth decades, with the majority of patients presenting in the second and third decades of life.

The lesion distribution revealed that benign lesions formed the largest category, comprising 12 cases. These included osteochondroma, non-ossifying fibroma, simple bone cyst, aneurysmal bone cyst, and fibrous dysplasia. Indeterminate lesions accounted for 2 cases and consisted of fibrous dysplasia lesions demonstrating heterogeneous post-contrast enhancement, warranting interval imaging follow-up. Aggressive lesions constituted 6 cases and included osteosarcoma, giant cell tumour with cortical destruction and soft tissue extension, simple bone cyst with pathological displaced fracture, and multiple myeloma.

The application of Bone-RADS enabled systematic lesion characterization and facilitated stratification into benign, indeterminate, and aggressive categories, thereby assisting in appropriate management recommendations and reducing diagnostic ambiguity.

DISCUSSION

The evaluation of bone lesions on MRI remains a diagnostic challenge because of the overlapping imaging features between benign, indeterminate, and malignant entities. The recently introduced American College of Radiology (ACR) Bone Reporting and Data System (Bone-RADS) provides a structured framework for characterization and management of incidental solitary bone lesions, thereby improving reporting uniformity and reducing variability among radiologists [1]. In the present study, Bone-RADS demonstrated practical utility in categorizing lesions into benign, indeterminate, and aggressive groups with corresponding management recommendations.

In our study, benign lesions constituted the majority of cases (60%). Common benign entities included osteochondroma, non-ossifying fibroma, simple bone cyst, aneurysmal bone cyst, and fibrous dysplasia. These lesions demonstrated characteristic MRI features such as well-defined margins, narrow zones of transition, absence of aggressive periosteal reaction, preserved cortical integrity, and lack of significant soft tissue extension. Similar findings have been extensively described in previous musculoskeletal imaging studies emphasizing that benign lesions typically exhibit non-aggressive imaging characteristics and geographic patterns of bone destruction [2,3]. The predominance of benign lesions in our study is also consistent with prior reports evaluating incidental bone lesions detected on MRI examinations [1,8].

Fibrous dysplasia represented both benign and indeterminate categories in our series. Although usually benign, fibrous dysplasia may occasionally demonstrate atypical imaging appearances including heterogeneous enhancement, cystic degeneration, haemorrhage, or secondary aneurysmal bone cyst formation, making differentiation from aggressive lesions challenging [4,9]. In our study, two cases with heterogeneous post-contrast enhancement were categorized as indeterminate and required interval imaging follow-up. This highlights the value of Bone-RADS in appropriately stratifying lesions that do not exhibit overt malignant features but cannot be confidently labelled benign.

Aggressive lesions accounted for 30% of the study population and included osteosarcoma, giant cell tumour with cortical destruction and soft tissue extension, pathological fracture associated with simple bone cyst, and multiple myeloma. MRI findings suggestive of aggressive behaviour included cortical breach, marrow replacement, periosteal reaction, heterogeneous enhancement, surrounding marrow oedema, and soft tissue extension. These imaging features are recognized indicators of malignancy or locally aggressive behaviour in musculoskeletal radiology literature [5,10].

Osteosarcoma in our series demonstrated classical aggressive MRI features including marrow replacement, cortical destruction, periosteal reaction, and extraosseous soft tissue extension. MRI plays a crucial role in local staging, assessment of neurovascular involvement, and surgical planning in osteosarcoma [11]. Giant cell tumour showed expansile osteolytic morphology with cortical thinning, cortical breach, and soft tissue extension, findings which correlate with previous studies describing the locally aggressive behaviour of giant cell tumours despite their benign histology [6]. Similarly, multiple myeloma demonstrated infiltrative marrow lesions with cortical destruction and associated soft tissue components, which are characteristic MRI hallmarks of plasma cell neoplasms [7].

The use of MRI in conjunction with Bone-RADS provides several advantages in lesion characterization. MRI offers superior marrow contrast resolution and improved evaluation of soft tissue extension, internal matrix, neurovascular involvement, and pathological fractures compared with conventional radiography and CT [12]. Structured reporting systems such as Bone-RADS also improve communication between radiologists and referring clinicians, assist in risk stratification, and guide recommendations regarding follow-up imaging, biopsy, or oncologic referral [1]. Additionally, standardized reporting may improve diagnostic confidence and reduce interobserver variability, particularly among less experienced radiologists.

Previous studies have emphasized the importance of combining imaging morphology, enhancement characteristics, lesion margins, and clinical features in differentiating benign from malignant bone tumors [13,14]. Bone-RADS integrates these principles into a practical and reproducible framework for routine clinical use. Our findings support its utility in daily musculoskeletal MRI practice and demonstrate its applicability across a spectrum of benign, indeterminate, and aggressive lesions.

The present study has certain limitations. The sample size was relatively small, and histopathological confirmation was not available for all benign lesions. Some diagnoses relied on characteristic imaging findings and clinical follow-up. Additionally, this was a single-center observational study, which may limit generalizability. Larger multicentric studies with long-term follow-up are required to validate the reproducibility and diagnostic accuracy of Bone-RADS in diverse patient populations.

Overall, our findings support the usefulness of the ACR Bone-RADS system as an effective standardized MRI-based classification tool for bone lesions. Its application assists in differentiating benign from aggressive lesions, guides management decisions, reduces diagnostic ambiguity, and may contribute to improved patient care in musculoskeletal imaging practice.

CONCLUSION

The ACR Bone-RADS classification system provides a practical and standardized approach for the evaluation of bone lesions on MRI. In our study, Bone-RADS effectively differentiated benign, indeterminate, and aggressive lesions based on imaging characteristics, thereby aiding in appropriate risk stratification and management planning. Benign lesions constituted the majority of cases, while aggressive lesions demonstrated characteristic features such as cortical destruction, periosteal reaction, marrow replacement, and soft tissue extension. The structured reporting framework improved diagnostic confidence and facilitated clear communication between radiologists and clinicians. Overall, Bone-RADS serves as a valuable tool in musculoskeletal imaging practice by reducing diagnostic ambiguity, guiding follow-up recommendations, and assisting in timely identification of lesions requiring biopsy or oncologic referral. Further large-scale multicentric studies are recommended to validate its diagnostic accuracy and reproducibility.

REFERENCES

1. Amini B, Dalili D, Fox MG, et al. ACR Bone-RADS: Bone Reporting and Data System for incidental solitary bone lesions on CT and MRI. J Am Coll Radiol. 2022;19(9):1044-1054.
2. Kransdorf MJ, Murphey MD. Imaging of soft tissue tumors. 4th ed. Philadelphia: Lippincott Williams & Wilkins; 2013.
3. Davies AM, Sundaram M, James SLJ. Imaging of bone tumors and tumor-like lesions: techniques and applications. Berlin: Springer; 2009.
4. Resnick D. Diagnosis of bone and joint disorders. 5th ed. Philadelphia: Saunders Elsevier; 2005.
5. Dorfman HD, Czerniak B. Bone tumors. St Louis: Mosby; 1998.
6. Murphey MD, Nomikos GC, Flemming DJ, Gannon FH, Temple HT, Kransdorf MJ. Imaging of giant cell tumor and giant cell reparative granuloma of bone. Radiographics. 2001;21(5):1283-1309.
7. Kyle RA, Rajkumar SV. Multiple myeloma. Blood. 2008;111(6):2962-2972.
8. Franchi A. Epidemiology and classification of bone tumors. Clin Cases Miner Bone Metab. 2012;9(2):92-95.
9. Greenspan A. Benign bone-forming lesions: osteoma, osteoid osteoma, and osteoblastoma. Clin OrthopRelat Res. 1993;(204):204-212.
10. White LM, Kandel R, Wunder JS, Bell RS, Blackstein ME, Schweitzer ME. Imaging of primary bone tumors and tumor-like lesions of bone. Radiographics. 2022;42(3):789-812.
11. Sundaram M, McGuire MH, Herbold DR. Magnetic resonance imaging of bone tumors and tumor-like lesions. Skeletal Radiol. 1988;17(1):2-18.
12. Jee WH, McCauley TR, Lee SH, et al. Chondroid tumors of the appendicular skeleton: differentiation with MR imaging. Radiology. 1998;209(2):349-356.
13. Stacy GS, Kapur A. Mimics of bone and soft tissue neoplasms. Radiol Clin North Am. 2011;49(6):1261-1286.
14. Hudson TM. Fluid levels in aneurysmal bone cysts: a characteristic finding on MR images. AJR Am J Roentgenol. 1984;143(5):1009-1010.
15. Campanacci M. Bone and soft tissue tumors. 2nd ed. Vienna: Springer-Verlag; 1999.
16. Bloem JL, Reidsma II. Bone and soft tissue tumors of hip and pelvis. Eur J Radiol. 2012;81(12):3793-3801.
17. Vanel D, Shapeero LG, Tardivon A, et al. MR imaging in the follow-up of malignant and aggressive bone tumors. Eur J Radiol. 1997;25(3):223-229.
18. Adams H, Doyle AJ. MRI of primary bone tumors. Cancer Imaging. 2004;4(1):74-80.
19. Ulano A, Bredella MA, Burke P, et al. ACR Appropriateness Criteria® primary bone tumors. J Am Coll Radiol. 2017;14(5 Suppl).
20. Fletcher CDM, Bridge JA, Hogendoorn PCW, Mertens F. WHO classification of tumours of soft tissue and bone. 4th ed. Lyon: IARC Press; 2013.