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1. G rading growth rate of lytic bone tumors and bone - RADS

2. INTRODUCTION The evaluation of bone tumors with plain radiography has been extensively studied. The inherently strong contrast between bone and soft tissue and the high spatial resolution of radiography allow for the evaluation of even subtle morphological distortions of bone structure. In the context of evaluating a bone tumor with radiography, the radiologist’s task is twofold: to provide information on (1) growth rate (2) entity of the lesion . The first task of providing information on the growth rate is of major importance , since fast growth rates indicate malignancy of the bone tumor . Fast growth rates estimated with radiography are known to be associated with decreased patient survival and poorer prognosis

3. T he reaction pattern of the local bone tissue depends on the growth rate of the tumor. Therefore, radiography remains an indispensable modality for the evaluation of bone tumors. Various classification systems have been developed in order to help radiologists completing these tasks. The classification system developed in 1980 by Gwilym Lodwick has become the textbook standard for grading bone tumor growth . In daily clinical practice, the applied classification is frequently referred to as such (“Lodwick grades I–III”). However, it has been argued that the original Lodwick classification system is complex and requires simplification . Therefore, the aims of the present article is to provide an easy-to-use decision tree of the original Lodwick grading algorithm suitable for teaching of students and residents with an illustration that may be used in clinical practice.

4. The decision tree T he Lodwick grading algorithm, four descriptors were selected for evaluation of a lytic bone tumor on radiography. These comprise (1) pattern of bone destruction, including the subdescriptor “margin” for the category geographic destruction; (2) penetration of cortex (3) sclerotic rim and (4) expanded shell. These four descriptors are the basis for the following sequential categorization, finally resulting in the growth grades IA, IB, IC, II, and III

5. DEFINITION AND SUBTYPES A geographic pattern is defined as “single or confluent hole in bone,” A moth-eaten pattern is defined as “multiple, apparently randomly distributed holes which [...] lack uniformity of size,” A permeative pattern is defined as “multiple uniformly small holes present anywhere in the lesion” .

6. For the geographic pattern, additional evaluation is required regarding the margin of the lesion. With regular margin With lobulated margin With multicentric margin With ragged or poorly defined margin Moth eaten With moth-eaten margin ≤ 1 cm With moth-eaten margin > 1 cm Permeative Penetration of cortex Absent Partial Total Sclerotic rim Present Absent Expanded shell Absent ≤ 1 cm > 1 cm

7. To assign growth grade III, the permeative pattern only needs to be present in part of the lesion. classified as growth grade II if a moth-eaten margin > 1 cm is observed If there is total penetration of cortex growth grade IC is assigned, irrespective of the actual margin descriptor(regular/lobular/multicentric/ ragged/poorly defined). A thin moth-eaten margin also leads to assignment of growth grade IC . If there is an expanded shell > 1 cm without a moth-eaten margin, without/partial penetration of cortex, and with a sclerotic rim, growth grade IB is assigned. Growth grade IB is also assigned if there is a geographic lesion with an incomplete sclerotic rim, without a moth- eaten margin and without/partial penetration of cortex growth grade IA: regular/lobulated/multicentric margin, no/partial penetration of cortex, sclerotic rim, no or slightly expanded (≤ 1 cm) shell

8. Grade III A 74-year-old man. A barely visible osteolytic bone tumor is observed in the diaphysis of the left tibia (solid arrow); margins are poorly defined. There is permeative tumor growth in the adjacent lateral cortex (dashed arrow). This latter point prompts the assignment of Lodwick growth grade III, irrespective of any descriptor of the adjacent lucency . The tumor proved to be a metastasis from a caecal carcinoma

9. Grade II A 54-year-old woman. One larger ill-defined lytic bone tumor is observed (solid arrow). Distal to this lesion are several round/oval smaller lytic lesions of varying size (dashed arrows). This is a moth-eaten pattern of bone destruction, i.e., Lodwick growth grade II is assigned. Note that if the larger lesion is considered the dominant (geographic) lesion, the overall resulting growth grade is still II—due to the width of the moth-eaten margin distally. This patient had multiple myeloma

10. Grade IC. A 71-year-old woman. A geographic lytic bone tumor in the proximal left humerus is observed. The tumor is geographic in nature and has a ragged and poorly defined margin (solid arrow). Total penetration of cortex is evident (dashed arrow) and results in assignment of Lodwick growth grade IC. The evaluation regarding a sclerotic rim and an expanded shell is not necessary to assign this growth grade. The tumor proved to be diffuse large B-cell non-Hodgkin Lymphoma

11. Grade IB. A 32-year-old man. A well-defined lytic bone tumor in the right superior pubic ramus is observed. The tumor is geographic in nature and has a regular to lobulated margin. There is thinning of the expanded shell, but no total cortical penetration. The shell is expanded beyond 1 cm of what is considered the normal contour of the superior pubic ramus (compare for contralateral side). Therefore, Lodwick growth grade IB is assigned. The tumor proved to be a chondromyxoid fibroma

12. Grade IB. A 43-year-old man. A well-defined tumor is observed in the proximal femur. No penetration of cortex is evident. A faint sclerotic margin is observed in parts of the lesion (solid arrow); other parts of the lesion do not show a sclerotic margin (dashed arrow). There is no expanded shell. Because the sclerotic margin is not visible around the entire lesion, Lodwick growth grade IB is assigned. MRI was performed for further evaluation; the lesion proved to be a lipoma

13. Grade IA. A 20-year-old woman. A lobulated, sharply marginated geographic tumor is observed in the medial distal metaphysis of the femur. There is no penetration of cortex; a sclerotic rim is observed (solid arrow). The contour of the cortex is normal (no expanded shell, dashed arrow). This is the combination of descriptors that leads to assignment of Lodwick growth grade IA. The appearance is considered typical for non-ossifying fibroma (NOF); a histological diagnosis is not warranted in such a case

14. SUBSEQUENT WORKS In 2016, Caracciolo and colleagues published a “Modified Lodwick-Madewell Grading System,” further refining the parameter changing margin . They suggested to introduce a new category IIIA for lesions with changes in margins on serial radiographs or for atypical combinations suggestive of malignancy when prior radiographs are not available, respectively. This category IIIA implies a high prob- ability of malignancy. Grade IIIB of this system contains Lodwick grades II and III. Radiographically occult lesions are assigned category IIIC Furthermore, grade IC becomes grade II to account for the moderate risk of malignancy of these lesions.

15. BONE- RADS The Bone-RADS scoring system includes four levels of risk — very low, L ow, I ntermediate H igh — with corresponding scores of 1, 2, 3, and 4 denoting increasing risk of malignancy while providing risk-aligned management recommendations

16. Key radiographic features included in the Bone-RADS scoring system predictive of risk of malignancy include: (1) margination, or zone of transition; (2) pattern of periosteal reaction (3) depth of endosteal erosion (4) presence or absence of pathological fracture (5) presence or absence of soft tissue mass.

17. 1. MARGINS Bone tumor risk stratification and management system: a consensus guideline from the ACR Bone Reporting and Data System Committee. Illustration of the modified Lodwick-Madewell Grading System of bone lesion margination. IA = geographic well-defined lesions with marginal sclerosis; IB = geographic well-defined lesions without marginal sclerosis; II = geographic lesions with ill-defined margins, originally designated IC by Lodwick, found to carry an intermediate risk of malignancy (approximately 50%); IIIA = lesions with changing margins; IIIB = nongeographic margins with moth-eaten or permeative osteolysis; IIIC = radiographically occult lesions with invisible margins.

18. Periosteal Reaction Periosteal reaction occurs as a result of external or intrinsic mechanical forces applied to cortical bone and is the process by which bones respond to stress, known as Wolff ’ s Law, which states that the pattern of periosteal reaction is a result of the duration or rate of change and intensity of the inciting factor. For example, chronic alterations in weight-bearing forces lead to cortical buttressing and solid periosteal new bone formation.

19. Nonaggressive patterns of bony remodeling —In remodelling the native cortex has slowly been replaced by a thin cortical shell, or neocortex, due to gradual concurrent endosteal resorption and periosteal new bone formation. (a) Smooth cortical - Pressure that is uniform in both time and space results in a smooth thin cortical shell (b) Ridged and septated cortical shell - A ridged and septated shell suggests that there have been variations in temporal and spatial growth rate (c) Lobulated cortical shell - more focal variations in growth rate result in a thin shell that appears more lobulated than ridged.

20. Aggressive patterns of periosteal reaction. Parallel spiculated, or “ hair-on-end, ” periosteal reaction often seen in osteosarcoma. (b) Divergent spiculated, or “ sun- burst, ” periosteal reaction also typical of aggressive neoplasms.

21. Patterns of periosteal reaction with intact native cortex . Dense and solid layers of periosteal new bone formation typical of an indolent bone lesion. (b) Codman ’ s angle, elevated and acutely disrupted periosteum, typical of an aggressive bone tumor with extra-osseous mass lifting and breaking through the surface periosteum. (c) Lamellated periosteal reaction, or “ onion-skinning, ” is often seen in aggressive etiologies including malignant neoplasms such as Ewing sarcoma but also benign etiologies such as osteomyelitis.

22. Complex or mixed patterns of periosteal reaction often seen in tumors with variable growth rates as may been seen in malignant transformation of a pre-existing benign bone tumor. Divergent spiculated periosteal reaction with Codman ’ s angles. (b) Lamellated and parallel spiculated periosteal reaction.

23. Endosteal Erosion. Endosteal pressure from a medullary bone lesion often results in endosteal erosions, or endosteal scalloping . The degree of erosion is graded as mild, moderate, and severe (grade 1, 2, and 3) and is relative to cortical thickness. Grade 1 or mild endosteal erosion is considered to be less than one-third of cortical thickness. Grade 2 or moderate endosteal erosion is between one- and two-thirds of cortical thickness. Grade 3 or severe endosteal erosion is greater than two-thirds cortical thickness or cortical disruption. Greater degree or depth of scalloping suggests increased biologic activity and increased risk of malignancy

24. Bone-RADS 0 (a) Anteroposterior radiograph of the right shoulder demonstrates an osteolytic lesion of the scapula, partially obscured by overlying humeral head — margins and cortical breakthrough are not well evaluated and therefore additional imaging was recommended. (b) Axial CT demonstrates soft tissue mass with cortical destruction and extra-osseous extension of disease; subsequent biopsy con fi rmed plasmacytoma.

25. Bone-RADS 1 Anteroposterior radiograph of the right ankle of a 15-year-old female patient demonstrating an eccentric distal tibial bone lesion with circumferential sclerosis (modi fi ed Lodwick-Madewell grade IA lesion) pathognomonic for non ossifying fi broma. Oblique radiograph with similar fi ndings. (c) Application of Bone-RADS system giving 1 point for margins (IA geographic well-de fi ned lesions with marginal sclerosis). and 0 points for all other features yielding point total = 1 and Bone-RADS score of 1.

26. Bone-RADS 2 (a) Anteroposterior and lateral radiographs of the left knee of a 59-year-old woman demonstrating a well-de fi ned geographic osteolytic proximal tibial bone lesion with incomplete marginal sclerosis (modi fi ed Lodwick-Madewell grade IB lesion) and moderate medial endosteal scalloping. Given patient age, routine blood work including complete blood count, complete metabolic pro fi le, lactate dehydrogenase, alkaline phosphatase, erthrocyte sedimentation rate, C-reactive protein, serum protein electrophoresis and urinalysis was performed, and an MRI was requested for further evaluation of the bone lesion. (b) Axial T1-weighted, short tau inversion recovery, and contrast-enhanced MR images demonstrate a simple appearing unicameral bone cyst with mild cortical thinning and minimal periostitis. (c) Application of Bone-RADS system

27. Bone-RADS 3 Anteroposterior radiograph of the knee of an elderly patient status post – remote lateral plate of screw fi xation of the femur demonstrating a geographic well-de fi ned osteolytic lesion with hazy surrounding marginal sclerosis (modi fi ed Lodwick-Madewell grade IA lesion) and lamellated periosteal reaction. Application of Bone-RADS system giving 1 point for margins, 4 points for periosteal reaction, and 0 points for all other features yielding point total = 5 and Bone-RADS score of 3. Subsequent biopsy revealed in fl ammatory cells with positive cultures consistent with Brodie ’ s abscess.; IIIA-C = lesions with changing margins, nongeographic margins with moth-eaten or permeative osteolysis, and radiographically occult lesions with invisible margins identi fi ed by other imaging modalities.

28. Bone-RADS 4 (a) Anteroposterior radiograph of the elbow of a 66-year-old male patient presenting with elbow pain and no known history of malignancy demonstrating a geographic but ill-de fi ned osteolytic lesion of the distal humerus (modi fi ed Lodwick-Madewell grade II lesion) with pathological cortical fractures. (b) Application of Bone-RADS system giving 5 points for margins, 2 points for pathological fracture, and 0 points for all other features yielding point total = 7 and Bone- RADS score of 4. Subsequent biopsy con fi rmed poorly differentiated carcinoma of unknown primary site. Further workup revealed other osseous and abdominal visceral metastases as well as a scalp lesion, which was biopsied and consistent with carcinoma.