Bone and Soft Tissue Tumors

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Bone Tumors: Basics & Benign - Gentle Giants

  • Approach: Age, location (epiphysis, metaphysis, diaphysis), margins (Lodwick: geographic IA/IB = benign; IC/moth-eaten/permeative = aggressive), matrix (osteoid, chondroid, fibrous), periosteal reaction (solid = benign; lamellated, sunburst, Codman = aggressive).
  • Common Benign Tumors:
    • Osteochondroma: Most common. Metaphyseal, cartilage-capped exostosis.
    • Giant Cell Tumor (GCT): Epiphyseal, lytic, "soap bubble". Locally aggressive.
    • Enchondroma: Medullary cartilage lesion. Hands/feet.
    • Fibrous Dysplasia: Ground-glass matrix.
    • Non-Ossifying Fibroma (NOF): Eccentric, lytic, sclerotic rim.
    • Aneurysmal Bone Cyst (ABC): Expansile, fluid-fluid levels. Giant Cell Tumor X-ray and Diagram

⭐ Osteochondroma is the most common benign bone tumor, typically presenting as a painless mass in adolescents.

Malignant Bone Tumors: Part 1 - Bad to the Bone

  • Osteosarcoma (OS)
    • Most common primary bone malignancy (excl. myeloma). Pain, swelling.
    • Age: Peak 10-20 yrs; also >65 yrs (secondary: Paget's, radiation).
    • Site: Metaphysis (distal femur, prox. tibia/humerus).
    • X-ray: Sunburst, Codman's triangle, cloud-like osteoid. Osteosarcoma X-ray: Codman's triangle and sunburst pattern
  • Ewing Sarcoma (ES)
    • Aggressive small round blue cell tumor; 2nd common in children.
    • Age: Peak 10-20 yrs.
    • Site: Diaphysis (long bones like femur), flat bones (pelvis).
    • X-ray: Onion-skin periostitis, moth-eaten destruction, large soft tissue mass.
    • Genetics: t(11;22) EWS-FLI1. 📌 "EWING t(11;22)"

⭐ Ewing Sarcoma often presents with systemic symptoms (fever, weight loss, ↑ESR), mimicking osteomyelitis.

Malignant Bone Tumors: Part 2 & Staging - More Meanies & Mapping

  • Chondrosarcoma:
    • Malignant cartilage. Age: >40 yrs.
    • Sites: Pelvis, femur, ribs.
    • X-ray: "Rings & arcs", popcorn calcification.
    • Chondrosarcoma X-ray with rings and arcs calcification
  • Multiple Myeloma (MM):
    • Commonest primary bone malignancy. Age: >50 yrs.
    • X-ray: "Punched-out" lytic lesions, vertebra plana.
    • 📌 CRAB: HyperCalcemia, Renal failure, Anemia, Bone lesions.
    • Multiple Myeloma Skull X-ray with Punched-Out Lesions
  • Adamantinoma:
    • Rare, low-grade. Site: Tibial diaphysis.
    • X-ray: "Soap bubble" appearance.
  • Staging: Enneking system (Grade, Site, Metastasis) guides therapy.

Key Malignant Bone Tumors Comparison:

FeatureOsteosarcomaEwing's SarcomaChondrosarcoma
Peak Age10-20 yrs10-20 yrs>40 yrs
SiteMetaphysis (knee)Diaphysis (long bones)Pelvis, prox. femur
X-raySunburst, Codman's $\triangle$Onion skin, lyticRings & arcs calc.

Soft Tissue Tumors & Mimics - Beyond the Bone

  • Soft Tissue Tumors (Key Examples):
    • Lipoma: Benign. Pure fat signal (T1/T2 hyper, fat-sats). Thin, few septa.
    • Liposarcoma: Malignant. Thick septa (>2 mm), nodular non-fatty areas, enhancement.
      • Well-differentiated: Often large, deep-seated.
      • Myxoid Liposarcoma: T2 hyperintense (myxoid stroma), "pseudocapsule", characteristic enhancement.
    • Synovial Sarcoma: Juxta-articular, young adults (15-40 yrs), calcification (~30%), "triple sign".
    • MPNST (Malignant Peripheral Nerve Sheath Tumor): NF1 association. Spindle cell tumor.
  • Common Tumor Mimics (Bone & Soft Tissue):
    • Non-Ossifying Fibroma (NOF): Eccentric, cortically-based lucency, sclerotic rim, "bubbly". Self-resolves.
    • Fibrous Dysplasia: "Ground-glass" matrix, expansile.
    • Myositis Ossificans: Zonal ossification, peripheral maturation. Early phase can mimic sarcoma.
    • Hematoma: Signal varies with age. No true enhancement of collection.
    • Abscess: Rim-enhancing collection, surrounding inflammation.

⭐ A key differentiator for liposarcoma vs. lipoma on MRI is the presence of thick septa (>2 mm), nodular or globular non-adipose components, and enhancement of these non-fatty areas.

High‑Yield Points - ⚡ Biggest Takeaways

  • Osteochondroma: Most common benign bone tumor.
  • Multiple Myeloma: Most common primary malignant bone tumor overall.
  • Osteosarcoma: Most common non-hematopoietic primary malignant bone tumor; metaphyseal, Codman's triangle, sunburst spiculation.
  • Ewing's Sarcoma: Diaphyseal, t(11;22), onion-peel reaction, small round blue cell tumor.
  • Giant Cell Tumor (GCT): Epiphyseal in skeletally mature patients, soap bubble appearance.
  • MRI is crucial for soft tissue sarcoma staging; Liposarcoma is most common in adults.

Practice Questions: Bone and Soft Tissue Tumors

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Soap bubble appearance on X-ray is seen in which bone tumor?

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Flashcards: Bone and Soft Tissue Tumors

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Radiological features of scurvy: Generalised _____

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Radiological features of scurvy: Generalised _____

osteopenia

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