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Home , Brown tumor, Cartilage tumor, Nonossifying fibroma

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 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) • 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 : • 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 away from the cortex, forming a triangle between the elevated periosteum and the bone cortex

• Periosteal Reaction: excludes fibrous dysplasia, , 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 • 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 Chondromyxoid 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 – and • “Rings-and-Arcs” • “Popcorn” • “Focal Stippled”

• 2) Osteoid Matrix: bone-forming tumors – osteoid , , 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 • 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 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: – 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 • “Vertebra Plana”: flattened vertebral body characteristic of EG in the spine • “Bony ”: central sclerosis in a lytic lesion • DDx: EG, , lymphoma, • 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 • 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 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. (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 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 that may be locally aggressive • Osteoblastoma and 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 (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 is considered in the differential, so should osteoblastoma • Commonly occur in the posterior elements of the vertebral bodies Osteoblastoma

Manaster. Osteoblastoma. StatDx. 2021. Brant, Helms. Fund. of Diagnostic Radiology. 2012. Metastatic Disease: should be considered for any lytic lesion – benign or aggressive in appearance – in a patient > 40 yo • Can have any radiographic appearance • Any metastatic process can present as a lytic, benign-appearing lesion • RCC is the only metastatic lesion that is said to always be lytic • Rare in patients < 40 yo, so usually not included in the differential unless there is a known primary RCC Metastases Myeloma: usually presents as a diffuse permeative process, but can present as a solitary lytic lesion or multiple lytic lesions • Plasmacytoma: bubbly lytic myelomatous lesion • Can precede hematologic evidence of myeloma by 3-5 years

Multiple Myeloma

Plasmacytoma Brant, Helms. Fund. of Diagnostic Radiology. 2012. (ABC): well-defined benign lucent expansile bone lesion • Primarily in patients < 30 yo • Typically present because of pain • Can present anywhere in the skeleton • Primary: no known cause or association with other lesions • Secondary: ABC can be a secondary due to trauma or occur as a component of giant cell tumor, osteosarcoma, , osteoblastoma, or fibrous dysplasia, for example • Mimic: Telangiectatic Osteosarcoma

• Radiography: • Lucent bone lesion • Virtually always aneurysmal or expansile • Rim of intact cortex • Non-sclerotic margins • Often seen in posterior elements of spine (differential includes osteoblastoma)

• CT/MR: • Fluid-fluid levels – Blood-filled spaces • Solid components: suggest ABC is secondary

Brant, Helms. Fund. of Diagnostic Radiology. 2012. Solitary Bone Cyst: common benign well-defined lytic bone lesion • Thought to arise as a defect during bone growth which fills with fluid and thins of the overlying cortex • Patient must be < 30 yo • Most occur in the proximal humerus and proximal femur, but can occur anywhere • Calcaneus is another common location – characteristically abut the inferior cortical surface • Usually asymptomatic unless fractured • Rarely form periostitis, even when fractured

• Radiography: • ALWAYS central in medullary cavity of bone • Fallen Fragment: classic sign of fractured solitary bone cyst – piece of cortical bone sinks to the dependent aspect of the lesion • Does not occur with any other lesion • Usually in metaphysis

Brant, Helms. Fund. of Diagnostic Radiology. 2012. Brown Tumors: continual loss of calcium in kidney disease results in rise of parathyroid hormone levels and resultant mobilization of skeletal calcium • Areas of rapid bone turnover are characterized by hemorrhage, granulation tissue, and fibrous tissue • Brown tumors usually undergo sclerosis and disappear once the underlying (HPT) is treated • Rarely seen anymore due to better recognition and treatment of kidney disease and HPT

• Radiography: • Can have almost any appearance – from purely lytic to sclerotic • Must have other radiographic findings of HPT to be considered • Subperiosteal : pathognomonic of HPT • Typically involves the radial aspects of the middle phalanges in the hands • Distal clavicles, medial proximal tibias, SI joints • Frayed, Cupped Growth Plates: in patients with open growth plates (pediatrics) – looks like rickets • Subtendinous and subligamentous bone resorption

Brant, Helms. Fund. of Diagnostic Radiology. 2012. Osteomyelitis: infection of the bone • : large focus of osteomyelitis • Can occur in any location • Can occur in patients of any age

• Radiography: • Cannot be reliably excluded by x-ray • +/- expansile • Can have sclerotic or nonsclerotic border • May or may not show periostitis • Some say infection should always be included in the differential of a lytic bone lesion • Some Helpful Signs: • When osteomyelitis involves the articular surface of a joint, there will be septic arthritis and resultant cartilage loss and/or effusion • Bony Sequestrum: small focus of bone centrally within a lytic bone lesion • Differential Diagnosis: Infection, Eosinophilic Granuloma, Lymphoma, Fibrosarcoma • Mimic: Osteoid Osteoma • Emphysematous Osteomyelitis: gas within bone adjacent to soft tissue infection

• MRI: Examination of Choice • Geographic replacement of normal medullary T1 signal hyperintensity Brant, Helms. Fund. of Diagnostic Radiology. 2012. Chondroblastoma: benign cartilage tumor arising in the of skeletally immature patients • Rare • Occur only in the epiphyses • Patient must be < 30 yo • Differential Diagnosis for Epiphyseal Lesion in Patient < 30 yo: infection (most common), chondroblastoma, giant cell tumor, ABC, geode (subchondral cyst) • Subchondral Cyst: can be diagnosed when there is a lytic lesion adjacent to an articular surface and arthritic change is present in the joint

• Radiography: • Epiphysis, eccentric • Well-defined lytic lesion • Sclerotic border and chondroid matrix • Differentiates from giant cell tumor

• MRI: • Prominent marrow and cortical edema • Periosteal reaction • Prominent soft tissue edema • Lesion itself often NOT T2 hyperintense Manaster. Chondroblastoma. StatDx. 2021. Brant, Helms. Fund. of Diagnostic Radiology. 2012. : benign lobulated cartilage tumor • Rare • Can be seen in a patient of any age

• Radiography: • No calcified matrix • Well-defined lytic metaphyseal lesion with thin sclerotic border • No periosteal reaction unless fractured • Resemble non-ossifying fibroma, but: • Can be seen in patient of any age • Often extend into the epiphysis • Can present with pain

Manaster. Chondromyxoid Fibroma. StatDx. 2021. Brant, Helms. Fund. of Diagnostic Radiology. 2012. Brant, Helms. Fund. of Diagnostic Radiology. 2012. Healed Lytic Bone Lesions: many lytic lesions that occur in patients < 30 yo will heal with a sclerotic appearance • For example: NOF, EG, ABC, solitary bone cyst, chondroblastoma • Consider these in patients between 20-40 yo

Benign Sclerotic Lesions: fibrous dysplasia, osteoid osteoma, infection, (healing), giant bone island, / osteonecrosis • Bone Islands: feathered margins of trabeculae blending with normal bone • Oblong, with long axis in the axis of stress on the bone • Bone Scan may be suggested if there is a concern for sclerotic metastases

Sclerotic Metastases: should be the top differential in patients > 40 yo

Brant, Helms. Fund. of Diagnostic Radiology. 2012. • Etiologies: trauma, steroids, sickle cell disease, Gaucher’s disease, EtOH, SLE • Radiographs: • Typical: lytic lesion with well-defined calcified serpiginous borders • Early: often negative; can show patchy sclerosis, mixed lytic-sclerotic, or even permeative appearance; multiple and diametaphyseal (bone infarcts) • Late: irregularity, fragmentation, collapse, secondary osteoarthritis (AVN)

Petersilge, Manaster. Osteonecrosis of Hip. StatDx. 2021. Brant, Helms. Fund. of Diagnostic Radiology. 2012. • MR: most sensitive and specific • Double Line Sign: inner high T2 (granulation tissue along interface of infarcted bone), outer low T2 (sclerotic bone seen on plain film) • Infarcted bone demonstrates fatty signal initially, then hemorrhage – edema – fibrosis • Adjacent edema correlates with pain, risk of collapse

32 yo with SLE 43 yo with SLE

Petersilge, Manaster. Osteonecrosis of Hip. StatDx. 2021. Patient Age is Critical! Malignant bone tumors can be correctly diagnosed 80% of the time just by using the patient’s age!

• Pediatrics: Osteosarcoma and Ewing sarcoma are the only childhood primary malignant tumors of bone

• Patients > 40 yo: only metastatic disease, multiple myeloma, and chondrosarcoma are common

• Between 30-40 yo: giant cell tumor, parosteal sarcoma, malignant fibrous histiocytoma, primary lymphoma of bone Ewing Sarcoma

Manaster. Ewing Sarcoma. StatDx. 2021. Brant, Helms. Fund. of Diagnostic Radiology. 2012. Osteosarcoma: malignant neoplasm of bone-producing cells • Most common primary malignant bone tumor • Almost always in children and young adults (< 30 yo) • Exception: Secondary osteosarcoma in older patients with Paget disease or history of radiation therapy • Usually occur toward the end of a long bone (metaphysis), but can be anywhere • Histologic Subtypes: • Classic (Conventional): most common • Telangiectatic: looks like ABC • Periosteal: medial distal femoral metaphysis • Parosteal: posterior distal femoral metaphsysis

• Radiography: • Destructive • Osteoid Matrix: solid, cloud-like • Sclerosis: from either new bone formation or reactive sclerosis • Occasionally can be entirely lytic (usually telangiectatic) • Codman’s triangle periosteal reaction

• MRI: will usually show a large soft tissue component and “skip lesions” (image joint to joint)

Brant, Helms. Fund. of Diagnostic Radiology. 2012. Parosteal Osteosarcoma: osteosarcoma arising on the surface of and growing outside the bone • Considered Low-Grade, unless it has extended into the medullary cavity • Osteoid Matrix: solid, cloud-like • Location: most commonly posterior distal femur, usually metaphyseal • String Sign: radiolucent line separating bulky tumor from cortex (“mushroom” or “cauliflower” appearance) • Reverse Zoning Phenomenon: mature bone starts in center and moves outward in parosteal osteosarcoma • Zoning Phenomenon: mature bone starts at periphery and moves inward in myositis ossificans

26 yo F with lateral knee mass for 2 months, but minimal pain

Manaster. Parosteal Osteosarcoma. StatDx. 2021. Don’t Touch Lesion: lesion with characteristic radiologic appearance – differential diagnosis should NOT be given because histologic analysis can be misleading

Myositis Ossificans: heterotopic formation of bone and cartilage in soft tissue with history of trauma • Histology: can mimic sarcoma, so biopsy could lead to inadvertent amputation

• Radiography: • Circumferential calcification with a lucent center • Zoning Phenomenon: mature bone starts at periphery and moves inward in myositis ossificans • If peripheral calcification cannot be determined on x-ray, delayed radiographs in 1-2 weeks can show interval development of peripheral calcifications • Otherwise, CT should be obtained

• MRI: Misleading • Peripheral calcification not well-seen • Edema in soft tissues often extends beyond the calcified rim and appears aggressive

Brant, Helms. Fund. of Diagnostic Radiology. 2012. Cortical Desmoid: benign avulsion injury of the adductor magnus muscle that can appear aggressive • Usually occur in young people • May or may not be associated with pain • Should become painless with rest • Can mimic an early parosteal osteosarcoma on imaging • Histology: can appear malignant, so biopsy could lead to inadvertent amputation

• Radiography: • Posteromedial supracondylar ridge of distal femur • May or may not show periosteal reaction • Saucer-shaped cortical lucency with adjacent sclerosis and periostitis

• MRI: • Often an incidental finding on knee MRI • Low T1, high T2 area of cortical irregularity

Brant, Helms. Fund. of Diagnostic Radiology. 2012. Ewing Sarcoma: aggressive tumor of small round blue cells with features of neuroectodermal differentiation • Usually in children and adolescents, but also in 20s (especially when in a flat bone) • 20-30% with metastases at diagnosis

• Radiography: • , centered in medullary cavity • Permeative (“moth-eaten”): no perceptible border (wide zone of transition) • Differential: includes EG and infection (all 3 can appear identical on radiographs) • Benign periostitis or a sequestration should remove Ewing sarcoma from the differential • Can be patchy and sclerotic • Periostitis: often onion-skin, but also sunburst

• MRI: often large associated soft tissue mass, but no associated ossification (detection of soft tissue mass difficult on plain film) Manaster. Ewing Sarcoma. StatDx. 2021. Brant, Helms. Fund. of Diagnostic Radiology. 2012. Chondrosarcoma: locally aggressive cartilaginous tumor • Usually in patients > 40 yo • Rarely in children • Can be very difficult to differentiate a low-grade chondrosarcoma from enchondroma • Key Differentiators: • Chondrosarcoma is PAINFUL • Aggressive periostitis • Cortical destruction • Size (> 4 cm in axial skeleton or flat bone) • Endosteal Scalloping (> 2/3 thickness) • Soft tissue mass • Neither radiologists nor pathologists can reliably distinguish enchondromas from low-grade chondrosarcomas

• Radiography: • Usually in metaphysis • Bony or soft tissue mass with “ring-and-arc” calcification in an older patient • Without chondroid calcifications, lesion is indistinguishable from other aggressive lytic lesions

• MRI: • Low to intermediate T1 signal • HIGH T2 SIGNAL

Brant, Helms. Fund. of Diagnostic Radiology. 2012. Metastatic Disease: • Should be included in any differential diagnosis of a bone lesion in patients > 40 yo

• Radiography: • Can have virtually any appearance • Characteristic Appearances: • Prostate Cancer: multiple sclerotic foci in a man • Almost any other metastatic lesion could present this way, including lung or colon cancer • Renal Cell Carcinoma: almost never is sclerotic • Expansile Lytic Metastases Differential: renal cell or thyroid carcinoma

Brant, Helms. Fund. of Diagnostic Radiology. 2012. : cartilage-capped bone growth • Malignant degeneration extremely rare, but more common with more axially situated lesions • Cartilage cap can degenerate into chondrosarcoma

• Radiography: • Metaphyseal • Two Morphologic Types: • Pedunculated: points away from the joint • Sessile: undulation of bone cortex • Cortex and marrow in continuity with the host bone • Otherwise lesion could represent a periosteal osteosarcoma

• MRI: • Cartilage Cap: < 2 cm in adults for benign osteochondroma • If cartilage cap > 2-3 cm, concerning for malignant degeneration to chondrosarcoma

• Associated Syndrome: • Multiple Hereditary : multiple distributed throughout the skeleton in a bilateral, symmetric fashion • Knees are nearly always involved • Undertubulation (widened diameter of bone) present at site of exostosis

Manaster. Osteochondroma. StatDx. 2021. Brant, Helms. Fund. of Diagnostic Radiology. 2012. What is the role? Cross-sectional imaging (CT and MRI) can be used to:

• 1) Further Characterize Lesions and Refine the Differential Diagnosis • CT: can better evaluate for matrix calcification • MRI: best for evaluating soft tissue tumors and some bone tumors • Lipomas, both soft tissue and intraosseous, are easily diagnosed on MRI • Radiographs: still the best for evaluating the great majority of bone tumors • On MRI, malignant tumors are usually characterized by low T1 and high T2 signal, but this is very nonspecific

• 2) Evaluate the Extent of a Lesion • MRI is often used to evaluate the extent of a bone tumor after radiographs and/or biopsy have established the diagnosis already • Classically done in the case of osteosarcoma Lipoma • Evaluates extent not only in bone, but also in adjacent soft tissues

Brant, Helms. Fund. of Diagnostic Radiology. 2012. Occasionally, bone tumors are poorly delineated on radiographs and CT. Example: Primary Lymphoma of Bone

45 yo M with 2 years of dull lateral knee pain – initially ignored. Pain worse at night and when trying to sleep. Pain acutely worsened over the last two weeks, now severe. No trauma or inciting event to bring about the symptomatic change. CT Protocol

• Usually Without Contrast: evaluating for matrix calcifications, which can be more difficult to evaluate on contrast-enhanced exam • With Contrast: may be needed in patients who cannot have an MRI • helps evaluate relationship of tumor to neurovascular structures, any soft tissue components • Axial CT acquisitions with coronal and sagittal reconstructions • Bone and soft tissue kernels

Parosteal Osteosarcoma

Manaster. Parosteal Osteosarcoma. StatDx. 2021. Brant, Helms. Fund. of Diagnostic Radiology. 2012. MRI Protocol

• Without and With Contrast • T1 • Best sequence when looking for the presence or absence of a bone marrow-replacing lesion • Necessary when evaluating soft tissue tumors (internal fat?) • T2FS (T2 with fat suppression) • Most pathologic entities will demonstrate T2 signal hyperintensity (edema) • Since fat signal is nulled, edema is much more obvious • +/- T1 FS • Fat will lose signal when compared with regular T1 • Not always necessary • T1 + Contrast • Evaluation for contrast-enhancing components – Yes or No? • Typically all sequences are done in all 3 planes (axial, sagittal, and coronal), but T1 post contrast does not need to be • If no fat-suppressed T1 was performed before contrast Simple Bone Cyst – T1 with Fat Suppression administration, this sequence should not be fat-suppressed • If you change two variables on the post-contrast images, increased signal in a mass could be due to the effect of fat suppression rather than actual contrast-enhancement

Brant, Helms. Fund. of Diagnostic Radiology. 2012. Large Differential Diagnosis: good thing is histology is much more straightforward compared to bone tumors

• Imaging Findings are Almost Always Nonspecific • Most Common Malignant Soft Tissue Tumors:

• 1) Undifferentiated Pleomorphic Sarcoma (UPS): • Older patients • Central location (proximal thigh, upper arm)

• 2) Liposarcoma: often have no internal fat on imaging • Spectrum of Fat-Containing Soft Tissue Masses • Lipoma: Almost completely fat • Hemangioma: Fat and soft tissue with internal flow voids (blood vessels) and phleboliths • Atypical Lipoma: Mostly fat-containing – few soft tissue components and internal septations • Aka well-differentiated liposarcoma • Liposarcoma: often no internal fat and indistinguishable from other malignant soft tissue tumors

• 3) Myxofibrosarcoma: tends to spread along fascial planes, creating characteristic tail-like margin and thick fascial enhancement at periphery Dinauer, et al. Radiographics. 2007. • Bone Tumors • Radiography is primary modality for diagnosis! • Always start with radiographs • CT: used for problem solving (matrix calcification) • MRI: used to further characterize and evaluate extent • Large differential diagnosis! • Use a step-wise approach for evaluation: • First Step: Sclerotic or Osteolytic? • Second Step: Well-defined or ill-defined margins? • Third Step: Patient age? • Fourth Step: Any other helpful clues? • Aggressive does NOT necessarily mean malignant (infection, EG) • Patient Age: critical to know when narrowing the differential diagnosis

• Imaging Appearance • Few bone tumors can be easily diagnosed on imaging appearance alone • Imaging characteristics, patient age, and history are necessary considerations

• Cross-Sectional Protocols • CT: Contrast usually not needed • MRI: Always without and with contrast 1. Brant WE, Helms CA. Fundamentals of Diagnostic Radiology, Fourth Edition. Section X: Musculoskeletal Radiology. Philadelphia, PA: Lippincott Williams & Wilkins, 2012. 2. Van der Woude HJ, Smithuis R. “Differential Diagnosis of Bone Tumors”. Radiology Assistant, Radiology Society of the Netherlands. 2010. https://radiologyassistant.nl/musculoskeletal/bone- tumors/differential-diagnosis 3. Manaster, BJ. “Osteoblastoma”. StatDx, Elsevier Inc. 2021. https://app.statdx.com/document/osteoblastoma/31e03d12-42d3-46d1-b3fa- ab71b2695aee?searchTerm=osteoblastoma 4. Manaster, BJ. “Chondroblastoma”. StatDx, Elsevier Inc. 2021. https://app.statdx.com/document/chondroblastoma/36d60cfd-f2f7-43c2-984c- 6628fda52d27?searchTerm=chondroblastoma 5. Manaster, BJ. “Chondromyxoid Fibroma”. StatDx, Elsevier Inc. 2021. https://app.statdx.com/document/chondromyxoid-fibroma/19f74f78-9f81-4e8c-a4e2- 77d36dd82eb8?searchTerm=chondromyxoid%20fibroma 6. Petersilge CA, Manaster, BJ. “Osteonecrosis of Hip”. StatDx, Elsevier Inc. 2021. https://app.statdx.com/document/osteonecrosis-of-hip/32e9afe2-e6e6-445b-97fa- 273d614efc98?searchTerm=avascular%20necrosis 7. Manaster, BJ. “Ewing Sarcoma”. StatDx, Elsevier Inc. 2021. https://app.statdx.com/document/ewing- sarcoma/203a2d8d-13da-4ea6-ab16-ea79857d46cd?searchTerm=ewing%20sarcoma 8. Manaster, BJ. “Parosteal Osteosarcoma”. StatDx, Elsevier Inc. 2021. https://app.statdx.com/document/parosteal-osteosarcoma/1d478b54-1317-48ad-8eda- 31edc9624394?searchTerm=parosteal%20osteosarcoma 9. Manaster, BJ. “Osteochondroma”. StatDx, Elsevier Inc. 2021. https://app.statdx.com/document/osteochondroma/2de40182-bde2-4aae-b855- 3152aee64898?searchTerm=osteochondroma 10. Dinauer PA, Brixey CJ, Moncur JT, et al. Pathologic and MR imaging features of benign fibrous soft- tissue tumors in adults. Radiographics. 2007; 27: 173-187. For more information, please contact:

Roland Holcomb, M.D. Diagnostic Radiologist Dakota Radiology Rapid City, SD [email protected]