Page 509 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat

Musculoskeletal, skin, and connective tissue ` pathology Musculoskeletal, skin, and connective tissue ` pathology section iii 465

Primary bone tumors (continued)
tUmoR typE EpidEmiology loCation ChaRaCtERistiCs
Malignant tumors
Osteosarcoma Accounts for 20% of 1° Metaphysis of long bones Pleomorphic osteoid-producing cells
(osteogenic sarcoma) bone cancers. (often in knee region). (malignant osteoblasts).
Peak incidence of 1° Presents as painful enlarging mass or
tumor in males < 20 pathologic fractures.
years. Codman triangle D (from elevation of
Less common in periosteum) or sunburst pattern on
elderly; usually 2° to x-ray E (think of an osteocod (bone
predisposing factors, fish) swimming in the sun).
such as Paget disease Aggressive. 1° usually responsive to
of bone, bone infarcts, treatment (surgery, chemotherapy),
radiation, familial poor prognosis for 2°.
retinoblastoma,
Li-Fraumeni syndrome.
Chondrosarcoma Medulla of pelvis, proximal Tumor of malignant chondrocytes.
femur and humerus.
Ewing sarcoma Most common in Diaphysis of long bones Anaplastic small blue cells of
Caucasians. (especially femur), pelvic neuroectodermal origin (resemble
Generally boys < 15 years flat bones. lymphocytes) F .
old. Differentiate from conditions with
similar morphology (eg, lymphoma,
chronic osteomyelitis) by testing for
t(11;22) (fusion protein EWS-FLI1).
“Onion skin” periosteal reaction in
bone.
Aggressive with early metastases, but
responsive to chemotherapy.
11 + 22 = 33 (Patrick Ewing’s jersey
number).
A B C

Round cell lesions
Ewing sarcoma Fibrous dysplasia
Diaphysis Myeloma D E F
Osteoid osteoma
Simple bone cyst

Metaphysis Osteosarcoma Osteochondroma

Physis
Epiphysis Giant cell tumor

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