Musculoskeletal Tumors Part 2
Part 2 of my review of musculoskeletal tumors for radiology board exam preparation. Download the free study guide on this and other topics here. Prepare to succeed!
Show Notes/Study Guide:
If you see a lytic lesion in a person who is older than 40 years old what should you consider first?
With a lytic lesion in a person who is greater than 40 years of age, metastasis or myeloma is the first consideration.
Does heterotopic ossification typically present with early peripheral calcification or early central calcification?
Heterotopic ossification classically presents with peripheral calcification with onset of roughly a month after injury. Malignancy is more likely to present with central calcification.
True of false: Myositis ossificans is a form of heterotopic ossification?
True. Myositis ossificans is typically post-traumatic in etiology and presents with peripheral calcifications at early stage. Myositis ossificans is actually the most common form of heterotopic ossification. Location within large muscles is common post-trauma. This is a “don’t touch” lesion. If you see this, get follow-up radiographs or CT instead of biopsy.
If you are given a history on a board exam question of a young male with nocturnal pain that improves with aspirin, what bone lesion is this history classic for?
Osteoid osteoma. This is a classic board exam question.
How do osteoid osteomas appear on imaging?
Lesion with cortical thickening and an intracortical nidus with variable calcification. Osteoid osteomas are also highly vascular on contrast-enhanced imaging. Note that an infection with Brodie’s abscess can appear similarly (Brodie’s abscess can present with various imaging appearances) but the clinical history will be different and should point you to a subacute to chronic infection rather than nocturnal bone pain relieved by aspirin.
What is the most common location of a Brodie’s abscess?
The tibial metaphysis (proximal or distal) followed by the femur. Can also involve the carpal/tarsal bones.
A calcaneal lesion that is bright on T1-weighted imaging and dark on MRI imaging with fat saturation is most suggestive of what lesion?
A calcaneal intraosseous lipoma. This location of an intraosseous lipoma is high-yield for board exams as this is the most common calcaneal bone lesion. Otherwise, an intraosseous lipoma is most common in the bones of the lower extremities. Look for fat density in the lesion on x-ray, CT, and fat signal with signal dropout on fat saturated images on MRI.
“Dripping candle wax” is a buzzword for what bone lesion?
Melorheostosis. This has an appearance of dripping candle wax related to cortical and medullary hyperostosis.
A Shepherd’s Crook Deformity is most typical for what lesion?
Polyostotic fibrous dysplasia. This is coxa varus angulation of the proximal femur. This can also be seen with osteogenesis imperfecta or Paget’s disease along with other entities.
True or False: A simple bone cyst is typically eccentric in location?
False. Aneurysmal bone cysts are typically eccentric in location whereas a simple bone cyst (aka unicameral bone cyst) is typically centered in the medullary space. Simple bone cysts are most classic in the humerus and are about 90% located in long bones. Remember the fallen fragment sign in which a fracture fragment falls dependently with gravity within the lesion is a sign of a simple bone cyst. Simple bone cysts are frequently first identified after a fracture occurs.
What is the most common bone tumor in young adults under 40 years of age?
Giant cell tumor. GCTs are most common in the distal femur followed by the proximal tibia and then the distal radius. GCTs are also more common in the sacrum and pelvis than the vertebrae. A GCT is a metaphyseal lesion with subchondral epiphyseal extension.
True or false: Giant cell tumors have sclerotic margins?
False. GCTs classically show non-sclerotic margins with a narrow zone of transition.
True or false: Aneurysmal bone cysts are commonly associated with a giant cell tumor?
True. There is a high association between GCTs and an aneurysmal bone cyst.
A “long lesion in a long bone” with groundglass matrix centered in the medullary space is most typical for what bone lesion?
Fibrous dysplasia which results from marrow being replaced by benign fibro-osseous tissue.
What are two common syndromes associated with polyostotic fibrous dysplasia?
McCune-Albright syndrome and Mazarbraud’s syndrome. Mazarbraud’s syndrome is classic for polyostotic fibrous dysplasia with myxomas. McCune-Albright syndrome is associated with café-au-lait spots and precocious puberty and/or other endocrinopathies to include Cushing’s syndrome. These are both high-yield entities for the ABR core exam.
What bone lesion is sometimes referred to as “a giant osteoid osteoma”?
Osteoblastoma, an osteoid osteoma-like lesion that is greater than 2 cm in size.
What is the most classic location for an osteoblastoma?
Posterior elements of the spine. These are expansile lesions located eccentrically in the medullary space in teens and young adults most commonly.
Chondroblastomas are most common in which age group and in which location?
Chondroblastomas are most common in the epiphyseal region of long bones, or in epiphyseal equivalents, and are most common in individuals under 20 years of age with male predominance. A chondroblastoma typically presents as a well-defined lytic lesion that may have internal calcification with adjacent metaphyseal periosteal reaction.
What are some of the “epiphyseal equivalents”?
Patella, calcaneus, trochanters, tuberosities, tarsal and carpal bones.
Non-ossifying fibromas are most common in what age group and in which location?
A non-ossifying fibroma is most common in young patients (ages 10-20) in the distal tibia and femur in a metadiaphyseal, cortical location. NOFs present with a narrow zone of transition and a sclerotic margin with no soft tissue mass or periosteal reaction. If <2-3 cm in size this may be termed a fibrous cortical defect. An NOF may also heal and become sclerotic.
What are common differential considerations for vertebra plana?
Mnemonic is MELT. Metastasis/Myeloma, Eosinophilic granuloma, Lymphoma, Trauma/Tuberculosis.
What are common imaging appearances for eosinophilic granuloma?
Beyond vertebra plana, EG may show the “hole-within-hole” appearance (lytic lesions asymmetric in both inner and out table of skull), may have a button sequestrum, and often appears as a well-defined medullary lucency “punched out lucency” with or without endosteal scalloping and periosteal reaction. However, EG can also appear aggressive and indistinct. Common locations include the skull, pelvis, femur and spine. Note that EG can also cause a “floating tooth” appearance. Most patients with EG will be under 20 years of age. Note that eosinophilic granuloma denotes skeletal involvement of Langerhans cell histiocytosis.
