Marlena Jbara, MD discusses imaging tools to assess bone tumors of the foot and ankle, general principles of imaging evaluation of bone tumors, as well as analyzing malignant bone tumors of the foot and ankle.
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TAPE STARTS – [00:00]
Marlena Jbara: My name is Marlena Jbara and for the next 30 minutes or so, we will be discussing bone tumors of the foot and ankle part 1. Disclosures: I or related party have no financial relationship to disclose. Objectives: To provide an overview of imaging tools used to assess all bone tumors of the foot and ankle. We will review general principles of imaging evaluation of all bone tumors, namely looking at the morphology, the age of the patient, the presence of matrix and the location within the bone. And in this session, we will look at an evaluation of malignant bone tumor of the foot and ankle. In our imaging toolbox, we are going to use x-rays, MRI, CT to look at bone tumors. We may go on to use chest CT or bone scan in order to stage or evaluate the bone lesion further. X-rays: So what's the point of obtaining x-rays. Well, x-rays can give an excellent assessment of growth rate, zones of transition, the presence or absence of periosteal reaction, can let us know whether a lesion is aggressive versus not aggressive. The matrix namely whether this is osseous, cartilaginous or fibrous matrix can be evaluated to identify the tumor type. MRI can be used to visualize the entire bone and the adjacent joint. What's great about MRI is that the superior soft tissue contrast. The ability to see within a tendon or within a ligament to identify whether the fibroids are torn.
We can identify skin metastasis that are seen in osteosarcoma and we can provide preoperative planning to identify the tumor proximity to adjacent neurovascular structures. We can use MRI to evaluate what the actual tissues or signals we see are and the way MRI works is basically is a frequency map of the resonation or the relaxation times of water and fat molecules. And when we weight it for fat molecules, we call that T1 weighting and when we weight the image for water molecules, that would be T2 weighted. And then we can look at different various substrates like hematoma or fat, fatty marrow, muscle and we can determine the relative T1 and T2 weighting to determine what that structure is made of on an amino acid level. So tumors are generally low T1 in signal and higher in T2 signal whereas Hyaline cartilage may have an intermediate T1 weighted signal and an intermediate T2 signal. Muscle tends to be about isointense considered on T1 weighted images and hemangiomas may have small flow voids and have intermediate signal intensity where it may be higher signal intensity on T2 weighted images. And there are many charts available to help you understand the MRI signal intensities of various tissues. CT offers superior special resolution, the ability to determine two separate points in space and this is useful to determine subtle cortical erosions and even calcifications or ossifications. The presence of matrix mineralization is much easier to see on CT as opposed to MRI.
In the evaluation of the bone neoplasm, we can take a process where we look at the morphology, assess the border whether there is bone destruction, periosteal reaction, the presence of matrix, cartilaginous, osseous or fibrous and the presence of soft tissue mass. We can see the location within a particular bone, what part of the bone would be involved, might be epiphysis, metaphysis, the diaphysis or even within the cross-section of bone whether it's central or eccentric. Looking at the age and sex of the patient can also give us an idea based on those other features of what would be the likely etiology of any given tumor and whether the presence of their single lesions versus multiple lesions as seen in the metastases and some multiple osseous syndromes further would give us clues as to the evaluation of the bone tumor. And the location within the skeleton, what bone, is it axial, is it appendicular skeleton, is it a flat bone, is it the skull? All these features can be used to help determine the etiology of any particular bone tumor. When we look at the bone tumor, we are going to look at the pattern of the bone destruction or morphology. And that comes in three flavors; geographic, moth-eaten and permeative. Let's begin with the discussion of geographic bone lesions. These are the least aggressive. The margins are clearly demarcated. They may have a sclerotic rim. There is generally a short zone of transition and they are benign lesions. So here we can see in this example to the right an aneurysmal bone cyst. This essentially has no zone of rim or sclerosis around it. So this would be, if we look at the bottom left, the different types of geographic lesions, we can have 1A, which is a sclerotic well-defined lesion.
We can have 1B, which would be a perforated well-defined lesion and 1C where there is really an imperceptible margin around the lesion, but we can definitely see where normal to abnormal bone is. In this case of this aneurysmal bone cyst, in the metaphysis is a geographic 1C lesion. And let's contrast that to this picture of the bottom right. This image demonstrating an intra-cortical lucent long lesion along the distal femur and we can see that would be on the order of a geographic 1A lesion with a rim sclerosis around it. The moth-eaten pattern is more aggressive. There are less well-defined margins, longer zones of transition and the differential diagnosis includes malignancy versus infection. This schematic on the bottom left demonstrates that there is a moth-eaten pattern here where you have this area of destruction with sort of irregular borders and a nice example to the right on this x-ray of right femur demonstrating these moth-eaten holes that are essentially going through the cortical and medullary bone. Here in this example above, you see the aggressive lesion with areas of lucency and periosteal reaction. Moving on to a permeative pattern, this is the most aggressive pattern. There is a rapid growth potential. There is a long zone of transition and it may emerge imperceptibly with the uninvolved bone and you can see a nice example here of this permeative pattern with Codman's triangle type aggressive periosteal reaction. Further on this example on the right proximal humerus of this lytic permeative lesion with cortical tunneling that you can see in the proximal humerus.
And of course this example further on to the right seeing this sclerotic aggressive permeative periosteal reaction with a long zone of transition. Bone malignancy also by age we can characterize primary bone tumors in the first year of life being usually the type of a neuroblastoma or statistically 1 to 10 years of age, they would have Ewing tumor. Moving on the 10 to 30-year-old category, this is where osteosarcoma and Ewing sarcoma still is in the differential. In the 30 to 40-year-old category, that's when we see more of the parosteal osteosarcoma and lymphoma. And more than 40 years of age, we will see metastases, multiple myeloma and chondrosarcoma. Moving on to a discussion of matrix and example on our left here, this cone down radiograph demonstrating the popcorn and ring-and-arch matrix identifiable in chondroid lesions. This image on your right demonstrating the osseous matrix with its cloud like snow storm and block sclerotic pattern. Matrix would give us an idea of this ring and arch type that cartilage tumors on the order of being an enchondroma in this case, but differential consideration with cartilage matrix producing tumors would be chondrosarcoma, chondroblastoma and chondromyxoid fibroma. In terms of bone tumors, we can see in this schematic that the small cell round blue cell lesions really like the diaphysis and that's the most common location where a chondroblastoma really prefers the epiphysis.
Tumors that occur on the physis include giant cell and aneurysmal bone cyst, osteosarcoma also likes the metaphysis but can be at risk and prone for skip lesions. Non-osteophyte fibromas are generally intracortical with endosteal scalloping and there are variety of these schematics to help guide us as to the common locations of bone tumors. Moving onto periosteal reaction, which can reflect the growing tumor that's eroding or penetrating the cortex and we can have these aggressive types of periosteal reaction, namely onion peel, Codman's triangle, sunburst and heron and and patterns as seen here on the right. So in summation, principles used to determine the etiology of a bone tumor will include the morphology, the age, matrix, the location of the lesion and the presence or absence of periosteal reaction. So now let's turn to looking at malignant tumors of the foot and ankle. I have included the most common players here including osteosarcoma, chondrosarcoma, Ewing sarcoma, metastases, and adamantinoma. I also will provide a rare case of leiomyosarcoma and some examples of lesions that mimic malignant tumors of the foot and ankle, namely infection and osteomyelitis. To begin with, malignant tumors of the foot and ankle are extremely rare. The Arm Forces Institute of Pathology states that osteosarcomas the most common followed by Ewing's and then chondrosarcoma.
In a recent cancer medical journal out of the British literature, they collected 7487 musculoskeletal tumors, 413 cases of which 5.5% were tumors of the foot and ankle. These were further stratified by 409 patients included, which were 215 male and 198 female patients. They recognized a total of 35 malignant tumors of the foot and ankle, of which chondrosarcoma was the most common in their series being 17 where osteosarcoma and metastasis were both six each and Ewing sarcoma, there was five cases of that. Osteosarcoma, so here is an example of sclerotic replacement of the entire calcaneus. We can see fragmentation along the edges with extension of osteosarcoma soft tissue mass. Here on these three versions of this MRI sequencing, we have at the top T1 weighted image and we can see that because the subcutaneous fat is indeed high in signal as is the bone marrow and this person is skeletally immature. We can see the growth plate here. To this bottom picture, we can see that this is a fluid sensitive sequence and we can see that most of the calcaneus is of low signal. There is peripheral rinds of increased signal with soft tissue mass extension. The middle image demonstrates the post contrast imaging where most of this lesion centrally demonstrates patchy minimal enhancement followed by thick, irregular areas of enhancement at its periphery with extension of the soft tissue mass.
And here we can see the amputated specimen, which lacks the normal calcaneal cortical borders and demonstrates the tumor eroding through the cortex and soft tissues as seen here, osteosarcoma of the calcaneus. Osteosarcoma, again matrix can be the solid sclerotic or cloud like stippled pattern or ivory like. Osteosarcoma represents less than 4% of osteosarcomas in total that arise in the foot and ankle. The main age of presentation is the fourth decade, which is later than for non-pedal osteosarcoma. Subtypes include intramedullary and surface or juxtacortical and the most common subtype would be the conventional high grade. This is about 80% are in the intramedullary type and those also include telangiectatic osteosarcoma and low grade osteosarcoma. There are also about 10% to 15% surface of juxtacortical and these include intracortical osteosarcoma, parosteal and aggressive periosteal osteosarcoma. Of course, about 5% are extra-skeletal osteosarcoma. In Ewing sarcoma, this is an aggressive primary round blue cell tumor. The male-to-female ratio is 1.5 to 1. The most common clinical presentation is that of pain and swelling. The femur and tibia are the most commonly effective sites.
Classically, you have a lytic destructive aggressive lesion with a soft tissue mass. And here I am demonstrating in this example to the left out of the literature, this version of a sclerotic Ewing sarcoma placing the fifth metatarsal diaphysis. This can occur in calcaneus and short tubular bones as well as metatarsals. There is a predilection for soft tissue invasion and metastasis and incidentally calcaneal lesions show a poor long-term survival. Ewing sarcoma as demonstrated here in this fifth metatarsal diaphysis with sclerotic tumor replacing the normal bone. We can see on the central image, this axial T1 short axis image demonstrating the star over the central aspect of the sclerotic fifth metatarsal diaphysis and the arrowheads pointing to the extension of the surrounding soft tissue mass. Here we can see furthermore the example of this central tumor pushing out the soft tissue tumor displacing the fourth metatarsal as denoted by the arrowheads. Moving on to chondrosarcoma, this is a malignant tumor or sarcomatous stroma producing cartilage. Lesions in the hand and foot are rare and represent about 1% to 3% of all chondrosarcomas. The peak prevalence is in the fourth to sixth decades. The tibia, fibula, tarsal and metatarsals are more frequently inflicted. It can arise from a preexisting osteochondroma or an enchondroma. Patients with hereditary multiple exostoses or Ollier's disease, which is multiple endchondromatosis or Maffucci's, which is enchondromatosis plus soft tissue hemangiomas are at higher risk.
In the foot, lesions typically low grade with potential for recurrence and the primary treatment is wide surgical excision, which is curative in the majority of cases. Schematic examples of cartilage matrix include a stippled flocculent or ring-and-arch variety of matrix deposition within a lesion. Here, I have included this recent pathologic fracture through this chondrosarcoma of the index metacarpal neck. Notice the stippled calcification within it and this chondroid matrix. In these two examples of chondrosarcoma, we can see in this example of the top left this CAT scan where there is this fungating lesion that's replacing the majority of the bones of the metatarsal region. And we can see here on this post contrast T1 fats [indecipherable] [19:18] peripheral high signals and tumor matrix. Here in this example to the right, notice this T2 high signal cartilaginous matrix. Cartilages are usually very bright on MRI, T2 weighted or proton density. And here, we can see this lesion on T1 weighted imaging on this short axis non-contrast, non-fat suppressed transaxial image. Chondrosarcoma and its mimickers; different osteolytic lesions of the calcaneus as demonstrated here.
In this example in A, we see this calcaneus with this patchy heterogeneous sclerosis that turned out to be Ewing sarcoma in a 31-year-old male patient. We have this simple bone cyst identified in this 11-year-old patient identified on the calcaneal body. In C, we have secondary squamous cell carcinoma and it's secondary to chronic osteomyelitis in an 82-year-old male patient. And D is a low-grade chondrosarcoma in a 45-year-old female. And this example here of leiomyosarcoma of the bone, I have included because I have a nice example but this is a very rare sarcoma. It accounts for less than 0.7% of all primary malignant bone tumors. It carries a very poor prognosis with a 35% overall survival rate and it usually requires a multidisciplinary team of experts in specialized referral centers to treat the lesion. And here, we can see a lesion from the literature where we have this left clavicular soft tissue mass replacing the bone. You can see in the bone window the irregular permeative pattern of the cortical destruction. In our example to the right, we can see that there is this tumor that's infiltrating at the lateral proximal tibia and sort of displacing the fibula laterally. What's frightening about this lesion is that this 54-year-old female came with ankle pain in September 23 in 2003 and you could see this loosened lesion here that was miscalled as a non-ossifying fibroma. And we can see when she returned six months later in March of 2004, it's well defined and of course at that point was imaged and you could see the leiomyosarcoma of bone.
Essentially, you see this tumor that's infiltrating between the lateral tibia and displacing the fibula laterally with the soft tissue mass that you can see on this coronal central image T1 weighted as low signal infiltrating the lateral tibia in the coronal plane. And of course, the coronal T2 correlate of this lesion with this lobulated, high signal aggressively going through the cortex of the distal tibia, leiomyosarcoma of bone. Of course, no discussion would be complete without metastases. This is most common in adults and the types of bone metastases are prostate, breast, lung, kidney, thyroid generally. We can remember the mnemonic of being lead-kettle PB-KTL. In children, metastases are often from small round blue cell tumors such as neuroblastoma, Ewing, osteosarcoma, malignant soft tissue tumors, Wilms and leukemia. The pathophysiology of metastases can be from direct extension of the tumor. Of course, retrograde blood flow, [indecipherable] [23:29] vertebral plexus can be way to disseminate metastases to the spine from the lungs, arterial seeding of course hematogenous seeding and distribution will include common sites of the vertebra, pelvis, proximal femur, proximal humerus, skull and we are going to initially begin our evaluation with an x-ray. And if we see a lesion on an x-ray, if it's just one lesion, we may want to further evaluate that with an MRI. And for the suspected metastasis, we may want to order a bone scan. So it depends on what we know about the patient whether they have a known or unknown primary at the time of diagnostic imaging.
And I have included some examples of renal cell metastases, which we can see here. This example on the left proximal humerus being this large lytic lesion and the central example being the axial image through the odontoid processes seen here sagitally with this large lytic lesion on the odontoid with pathologic fracture. And here is an example from an unknown primary where there is a bone marrow infiltrative lesion occupying the hamate. Here is what the hamate normally looks like on the left. You could see the lytic lesion on the right and further the MRI with the bone marrow replacement. Adamantinoma represents a rare primary malignant bone tumor. This is locally aggressive. Distal metastases have been reported in 15% of cases and in 10 to 50 year old category, about 50% of these lesions occur in the 10 to 30 year old group. About 90% of them more occur in the tibial diaphysis, so I have included it here. About 60% of these patients tell us a history of trauma and the differential diagnosis is broad. It includes giant cell long lesion such as fibrous dysplasia, bone cyst, aneurysmal bone cyst, eosinophilic granuloma and chronic osteomyelitis. Here is an example of 13-year-old with chronic pain. This was a biopsy-proven adamantinoma. Notice a long lesion and it's intracortical, it's bubbly lytic presence in the intracortical region.
And here is another example of an adamantinoma post contrast imaging demonstrating its cystic high signal post contrast additionally on this image on the left, the enhancement pattern. I wanted to take a moment to talk about osteomyelitis and Brodie's abscess and present these beautiful illustrations for transphyseal vessels being continuous to the metaphysis in the infant. So it's possible that infants that are born with hematogenous osteomyelitis may have actually have that in the epiphysis and even into the joint space for that matter at birth. Somewhere around two to three months of age, those epiphyseal, trans-epiphyseal vessels obliterate and we are left with the more classic patterns of subacute osteomyelitis that will eventually occur in the metaphysis. So a nutrient vessel comes into the diaphysis, goes down to the metaphysis, sludges in the sinusoids. If it has infection, it moves at a slow rate creating the ability for the bacteria to grow and multiply and you wind up getting your bone abscess in this location. Hematogenous osteomyelitis. And here is an example of a cystic lesion within the cuboids surrounded by patchy sclerosis as seen here on the AP and lateral exam. Here, an MRI demonstrating on the left transaxial T1 weighted imaging through the cuboid with low signal and cystic changes essentially on this image to the right with surrounding high signal change demonstrating edematous and inflamed bone.
And of course, short axis images demonstrating T1 changes in the post contrast enhancement of Brodie's abscess. And then of course, this percutaneous drainage procedure thorough the cuboid draining the abscess capsule. Brodie's abscess of the cuboid is subacute osteomyelitis and staph aureus is the most common. It's usually a painful well-defined geographic lytic lesions surrounded by diffuse sclerosis and the most common locations are going to be in the metaphysis of long bones about two thirds of them. The differential diagnosis includes tumor. Looks like an aggressive lesion. More examples of Brodie's abscesses here. Notice this lytic lesion located at the metaphysic, all of them Brodie's abscesses. In summary, I provided an overview of imaging tools used to assess all bone tumors of the foot and ankle. We reviewed general imaging principles of bone tumors including identifying morphology, age, matrix and location. I have provided an evaluation of the most common malignant bone tumors of the foot and ankle, namely osteosarcoma, chondrosarcoma, and Ewing sarcoma. We touched on metastasis, adamantinoma and of course, I added leiomyosarcoma of bone. We reviewed the differential diagnosis, which included Brodie's abscess and osteomyelitis. I thank you for your time and attention and these references are available for your review.
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