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40 Cards in this Set
- Front
- Back
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Are malignant bone tumors common?
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thankfully no
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What two "benign" conditions mimic malignant bone lesions...
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infection and EG
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What four conditions are given in standard text to differentiate malignant vs benign bone lesions?
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1. cortical destruction
2. periostitis 3. orientation or axis of the lesion 4. zone of transition |
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Descriptive terms for malignant periostitis...
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onion skin, amorphous or sunburst like.
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Benign periostitis looks...
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dense like callous of a bone....because it happens slower and has time to lay down more bone.
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Many benign lesions cause malignant looking periostitis so this isn't the greatest criteria....list some..
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EG, infection, trauma, osteoid osteoma, ABC all can...
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Detection of benign periostitis is more/less helpful than that of malignant....
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more helpful because malignant lesions wont cause benign periostitis unless there is concommitant fracture or infection. it is dense, wavy, thick.
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What does axis have to do with malignant characterization?
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Doesnt help much. It is said that if it grows with the axis it is most likely benign....too many exceptions.
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Most reliable plain film indicator for malignancy?
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Wide zone of transition.
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If a lesion has a wide zone of transition it can be said to be what?
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Aggressive but not necessarily malignant.
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Examples of benign lesions with a wide zone of transition.
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infection, EG
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Examples of lesions having permeative border....also a type of wide zone of transition...
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MM, reticulum cell sarcoma (primary lymphoma of bone), Ewing sarc are typical. Sometimes infection and EG.
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Differential of malignant bone lesions is long/short?
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short.
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What makes pinning a malignancy on bone lesions fairly easy?
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short differential and strict age categories.
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Bone malignancies age 1-30...
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Ewing sarc, orteogenic sarc.
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Malignant bone lesions age 30-40...
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giant cell tumor, parosteal ssarcoma, fibrosarcoma, malignant fibrous histiocytoma, primary lymphoma of bone.
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Malignant bone lesions age greater than 40...
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chondrosarcoma, metastatic dz, myeloma
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Plain film is best for _______and MR is used for_____in malignant bone lesions.
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Plain film dianosing. MR finding out extent both in skeleton and in soft tissues. If resection is contemplated MR should be performed.
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MR criteria for malignancy...
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irregular mass that can encase neurovascular structures or invade bone.
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Intensity on T1 and T2 with tumors?
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low T1 very high T2. there are a few exceptions (fibrosarc, malignant fibrous histiocytoma, desmoid occasionally all show low T2)
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List a few lesions (benign) better diagnosed on MR....
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lipomas, hemangiomas, avm's
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Gad should be administered to differentiate what from a tumor?
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fluid collection (effusion or bursa will have rim enhancement vs full enhancement with tumor)
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Most common malignant primary bone tumor?
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osteosarcoma
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Characteristics of osteosarcs....
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lots of times they are on ends of long bones but not always so not a good discriminator; destructive or lytic; many different types and classifications exist but radiologist neednt know them.
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What on MR helps diagnose an osteosarc?
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large soft tissue component with heterogenous high and low signal on both T1 and T2.
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Parosteal osteosarcoma...what is important to know?
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Radiologist plays an important role in deciding treatment. if it hasn't invaded into medullary region of bone it is shaved off. If it does it is treated like a central osteosarcoma as it is considered to be just as aggresive. MR or CT helps.
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What lesion can mimic parosteal osteosarc? (two)
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cortical desmoid (avulsion injury that is totally benign) or myositis ossificans.
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Ewing sarc description...(classic)
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permeative, diaphysis long bone, child (classically).
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what percentage of Ewing sarc is in diaphysis?
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only 40%...remainder being metaphyseal and in flat bones
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Other descriptive variations or characteristics of Ewings.
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Can be in adolescents and flat bone lesions often in people in their 20's. Most often permeative but can also be sclerotic and have patchy appearance.
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What kind of periostitis does Ewings have?
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onion skin or sunburst.
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classic ddx for a child with a permeative lesion...(3)
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Ewings, EG, infection
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chondrosarc appearance...
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protean
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what is difficult to differentiate from chondrosarc?
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enchondroma...histology is the same if it is low grade.
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what can help differentiate chondrosarc from enchondroma?
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pain...only use "possible chondrosarc" if pain is present because it can trigger wide excision.
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what radiologic study will help differentiate low grade chondrosarc from enchondroma?
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MR...if soft tissue mass or edema is present it is unlikely to be an enchondroma.
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any time there is a soft tissue mass with amorphous snowflake calcification in an older patient what dx should be considered?
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chondrosarc.
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Most malignant tumors do not need a radiologist to _____
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diagnose them...use the biopsy results
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what % of Giant Cell tumors are considered malignant...
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15%...rarely metastesize to lung. usually considered malignant for their recurrence rate.
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how do you tell giant cell malignant tumor from benign
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hard...rate of recurrence only...radiographically and histologically identical.
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