South Dakota Academy of Physicians Assistants (SDAPA) Virtual Conference, March 2021 Roland Holcomb, M.D., DABR Diagnostic Radiologist Dakota Radiology Rapid City, SD [email protected] By the end of this presentation, the participant should: • Know the role of imaging in the evaluation of musculoskeletal tumors • Understand basic cross-sectional imaging protocols in the evaluation of musculoskeletal tumors • Be familiar with the multimodality imaging appearance of select musculoskeletal tumors Target Audience: Physicians Assistants and Primary Care Practitioners Differential Diagnosis: mostly depends on appearance on radiographs and patient age • Most important characteristics for differential: • Morphology on X-ray: Well-defined osteolytic, ill-defined osteolytic, sclerotic • Most bone tumors are osteolytic • Age of patient: Metastases and myeloma always included on differential for > 40 yo patients • CT and MRI are only helpful in select cases Van Der Woude, Smithuis. Radiology Assistant. 2010. Brant, Helms. Fund. of Diagnostic Radiology. 2012. Benign vs Malignant? Oftentimes difficult, sometimes impossible • Some benign entities (i.e. eosinophilic granuloma, infection) can have an aggressive appearance typical of malignant entities • Radiologic (X-Ray) Criteria: • 1) Cortical Destruction • 2) Periosteal Reaction • 3) Orientation or axis of the lesion • 4) Zone of Transition: between lesion and adjacent normal bone (most important) • Only helpful in lytic lesions • Narrow, < 30 yo = Benign • Border can be traced with fine-point pen • Wide: Malignancy, Infection, EG • Aggressive, but not necessarily malignant • Step-Wise Evaluation of a Bone Tumor: • First Step: Sclerotic or Osteolytic? • Second Step: Well-defined or ill-defined margins? • Third Step: Patient age? Van Der Woude, Smithuis. Radiology Assistant. 2010. • Fourth Step: Any other helpful clues? Brant, Helms. Fund. of Diagnostic Radiology. 2012. Periosteal Reaction: Can be very helpful, as malignant lesions NEVER cause a benign periosteal reaction • Benign: Thick, wavy, uniform callus formation • From chronic irritation or fracture healing • Looks like cortical thickening • Aggressive: Multilayered, lamellated (onion- skinned), spiculated (sunburst), or Codman’s triangle • Spiculated: Periosteal reaction perpendicular to the cortex • Codman’s triangle: elevation of the periosteum away from the cortex, forming a triangle between the elevated periosteum and the bone cortex • Periosteal Reaction: excludes fibrous dysplasia, enchondroma, NOF, and SBC • Periosteal reaction is not always present Van Der Woude, Smithuis. Radiology Assistant. 2010. Cortical Destruction: common finding, not very useful for differentiating between malignant and benign • Complete Destruction: • High-grade malignancy • Aggressive benign etiologies like EG and infection Osteosarcoma • Local, Uniform Destruction: • Low-grade malignancy • Benign lesions • Ballooning: destruction of endosteal cortical bone and addition of new bone on outside occur at the same rate – “neocortex” • Endosteal Scalloping: • Benign lesions (e.g. fibrous dysplasia) • Low-grade chondrosarcoma Chondromyxoid Fibroma Giant Cell Tumor Van Der Woude, Smithuis. Radiology Assistant. 2010. Matrix Calcification: foci of calcification within a bone lesion can help narrow the differential diagnosis • CT may be recommended – shows matrix calcification much better than radiographs • Two Types: • 1) Chondroid Matrix: cartilaginous tumors – enchondromas and chondrosarcomas • “Rings-and-Arcs” • “Popcorn” • “Focal Stippled” • 2) Osteoid Matrix: bone-forming tumors – osteoid osteoma, osteoblastoma, osteosarcoma • Benign Tumors: Trabecular ossification • Osteosarcoma: • “Cloud-like” • “Ill-defined amorphous calcification” Van Der Woude, Smithuis. Radiology Assistant. 2010. Fibrous Dyplasia: developmental anomaly of bone formation – expansile lesion prevents mature lamellar bone from forming and medullary cavity is replaced by fibrous tissue and immature woven bone – seen in any age • Monostotic (85%) or Polyostotic (15%) • Monomelic: 1 side of the body • Polymelic: both sides of the body • Radiography: primary modality for diagnosis • NO PERIOSTEAL REACTION OR PAIN • Ground-glass matrix, purely lytic or sclerotic, well- circumscribed • Predilection for pelvis, proximal femur, ribs, skull • When present in pelvis, also present in ipsilateral femur • Can affect the proximal femur alone • MR: Variable Appearance • Expansile lesion • Hypointense bony trabeculae, cystic changes, septations, soft tissue expansion, pathologic fracture • Associated Syndromes: • McCune-Albright syndrome: FD, skin pigmentation, and endocrine abnormalities • Mazzabraud syndrome: FD and intramuscular myxoma Brant, Helms. Fund. of Diagnostic Radiology. 2012. Enchondroma: benign intramedullary cartilage neoplasm • Lobules of mature hyaline cartilage • May undergo enchondral ossification with chondroid matrix (“rings and arcs” pattern) • Radiography: • May be central, eccentric, expansile, or nonexpansile • Always contain calcified chondroid matrix • Except when in the phalanges – then purely lytic • Most common benign lytic lesion in the phalanges • Important Points: • Enchondroma can be indistinguishable from low-grade chondrosarcoma on histology • Diagnosis depends on correlation of clinical, imaging, and pathology findings • Enchondroma should have NO PERIOSTITIS OR PAIN unless pathologic fracture present • Pain is a better indicator of malignancy than x-ray appearance • No enchondromas occur in the pelvis or ribs! • If a lesion looks like enchondroma in these locations, it is actually chondrosarcoma! • No chondrosarcomas occur in the hands or feet – only enchondromas • Associated Syndromes: • Ollier disease: enchondromatosis – multiple, widespread, benign cartilaginous foci • Maffucci syndrome: enchondromatosis AND hemangiomas (phleboliths are the tipoff on radiographs) Brant, Helms. Fund. of Diagnostic Radiology. 2012. Eosinophilc Granuloma (EG): proliferation of large mononuclear cells with eccentric nucleus – derived from bone marrow stem cell CD34 – cells may infiltrate organs • Form of Histiocytosis X • Must be < 30 yo for this diagnosis! • Radiography: • Usually single bone lesions, but can be polyostotic • Variable appearance! • Lytic or sclerotic • Well-defined or ill-defined • +/- Sclerotic border • +/- Periosteal reaction (when present, usually thick, uniform, wavy) • Can mimic Ewing sarcoma • “Vertebra Plana”: flattened vertebral body characteristic of EG in the spine • “Bony Sequestrum”: central sclerosis in a lytic lesion • DDx: EG, osteomyelitis, lymphoma, fibrosarcoma • Patient age is best criterion for discrimination • EG could be mentioned in the DDx for any bone lesion in a patient < 30 yo Brant, Helms. Fund. of Diagnostic Radiology. 2012. Giant Cell Tumor (GCT): bone tumor believed to result from an over-expression of the RANK/RANKL signaling pathway with resultant hyperproliferation of osteoclasts • Contain numerous thin-walled vascular channels – likely related to relatively frequent coexistence of aneurysmal bone cysts (ABCs) • Lytic lesion (no matrix calcification) • Ends of long bones and flat bones • Can be benign or malignant – imaging and histology cannot differentiate • Malignant lesions recur, can metastasize to the lungs • Radiography: 4 Classic Radiographic Criteria for Diagnosis (all must be present) • 1) Occurs only in patients with closed growth plates • 2) Must be epiphyseal and abut the articular surface • Does not apply for lesions in flat bones or apophyses (i.e. greater trochanter, calcaneus) • 3) Eccentrically located, rather than central in medullary cavity • 4) Sharply defined zone of transition, NOT sclerotic • Does not apply for lesions in flat bones or apophyses (i.e. greater trochanter, calcaneus) Brant, Helms. Fund. of Diagnostic Radiology. 2012. Nonossifying Fibroma (Fibroxanthoma): benign, highly cellular bone lesion • Probably the most common bone lesion seen by radiologists • Seen in up to 20% of children – only rarely seen after 30 yo • Fill in with normal bone as they heal – become sclerotic – around 20-30 yo • NOF should not be considered in a patient > 30 yo • No periostitis or pain • NOF and Fibrous Cortical Defect are histologically identical – only difference is size • NOF is > 2 cm • FCD is < 2 cm • Radiography: • Well-defined focal lytic lesion • Cortically-based • Thin sclerotic, scalloped border • Slightly expansile • Typically in metaphysis of long bones • Characteristic Appearance: there should be Healing NOF no differential when one is seen on imaging Brant, Helms. Fund. of Diagnostic Radiology. 2012. Osteoblastoma: rare bone-forming tumors comprised of osteoblasts that may be locally aggressive • Osteoblastoma and Osteoid Osteoma are histologically very similar – only difference is size • Osteoblastoma is > 1.5 cm • Osteoid Osteoma is < 1.5 cm • Osteoid Osteoma: classic clinical presentation with dull pain, worse at night, minimal response to aspirin • Cortically-based sclerotic lesion with small lucent nidus centrally • Painful scoliosis when in the spine Osteoid Osteoma • Radiography: Variable appearance, but two main appearances to consider: • 1) Resemble large osteoid osteomas (sclerotic) • 2) Simulate aneurysmal bone cysts (ABCs) • Expansile • Lytic, soap-bubble appearance • Rim of reactive sclerosis / intact, thinned cortex • About ½ show speckled internal calcifications • If aneurysmal bone cyst is considered in the differential, so should osteoblastoma • Commonly occur in the