Soft Tissue Tumors

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STT Intro & Class. - Squishy Suspects

  • Definition: Soft Tissue Tumors (STT) are neoplasms from extraskeletal, non-epithelial (mesenchymal) tissues.
  • Epidemiology: Benign STT are common. Malignant STT (Sarcomas) are rare, <1% of adult malignancies, ~15% of pediatric malignancies.
  • Origin: Mesenchymal tissues (fat, fibrous, muscle, vessel, nerve).
  • Classification & Key Differences:
    • Benign: Slow growth, usually painless, well-circumscribed, rarely recur, no metastasis (e.g., lipoma, fibroma).
    • Malignant (Sarcomas): Rapid/aggressive growth, often painful, ill-defined margins, high recurrence, metastatic potential (e.g., liposarcoma, rhabdomyosarcoma). Soft Tissue Tumor Imaging: Clinical, X-ray, CT

⭐ Sarcomas typically metastasize hematogenously, most commonly to the lungs.

Benign STT - Friendly Lumps

MRI of giant cell tumor of tendon sheath

TumorTissue of OriginKey Clinical/Path Feature(s)Typical LocationSimple Management
LipomaAdiposeMost common STT; soft, mobile, painless, "slippage sign"SubcutaneousExcision if symptomatic
FibromaFibrousFirm, slow-growing; superficial (dermatofibroma) or deep (desmoid - locally aggressive)Extremities, trunkObservation, excision
HemangiomaBlood VesselRed/blue, compressible; capillary (strawberry) or cavernousSkin, muscle, synoviumSclerotherapy, laser, excision
NeurofibromaNerve SheathSoft, fleshy, "buttonholing sign"; assoc. NF1Peripheral nervesExcision if symptomatic
SchwannomaSchwann CellsEncapsulated, eccentric to nerve; Antoni A/B areasPeripheral nervesExcision (nerve sparing)
GCTTSSynoviumFirm, lobulated, painless mass; hemosiderin-laden macrophagesFingers, hand, wristMarginal excision

Malignant STT - Sinister Swellings

  • General: Rare, deep-seated, >5cm, rapid growth, pain.
  • Grading: FNCLCC (Fédération Nationale des Centres de Lutte Contre le Cancer) - based on differentiation, mitosis, necrosis.
  • Staging: AJCC TNM (Tumor, Node, Metastasis).

Histopathology of Well-Differentiated Liposarcoma

  • Common Sarcomas & Key Features:
    SarcomaKey Genetic/Histo FeatureCommon Site(s)Prognostic Factor
    LiposarcomaMDM2 amplification (well-diff/de-diff)Thigh, retroperitoneumSubtype, grade
    RhabdomyosarcomaEmbryonal (botryoid), Alveolar (PAX-FOXO1)Head/Neck, GU tractSubtype, age
    Synovial SarcomaSYT-SSX fusion (t(X;18)); biphasic patternExtremities (knee)Size, grade
    LeiomyosarcomaSmooth muscle differentiation; spindle cellsUterus, retroperitoneumGrade, location
    MPNSTNF1 association; S100+, SOX10+Trunk, extremitiesNF1 status, size

Rhabdomyosarcoma is the most common soft tissue sarcoma in children, often presenting in head/neck or GU tract.

STT Dx & Mgmt - Unmasking & Tackling

  • Clinical Evaluation: History (red flags: pain, rapid growth, size >5cm, deep to fascia), thorough physical exam.
  • Imaging:

    MRI is the imaging modality of choice for local staging and characterization of soft tissue tumors, detailing extent and neurovascular relations.

    • X-ray (calcification, bone changes), CT chest (metastases), PET-CT (high-grade, staging, response).
  • Biopsy: Image-guided core needle biopsy is standard; crucial for accurate diagnosis and grading before definitive treatment. MRI axial view of thigh soft tissue sarcoma with contrast
  • Treatment Principles: Multidisciplinary team (MDT) approach is essential.
    • Surgery: Aim for wide local excision with clear margins (R0 resection).
    • Radiotherapy: Neo/adjuvant use common for improved local control.
    • Chemotherapy: For chemosensitive types, advanced/metastatic disease, or neoadjuvant.

High‑Yield Points - ⚡ Biggest Takeaways

  • UPS (MFH): Most common soft tissue sarcoma (STS) in adults.
  • Rhabdomyosarcoma: Most common STS in children; embryonal subtype most frequent.
  • Synovial Sarcoma: t(X;18) translocation (SYT-SSX); juxta-articular, not truly synovial.
  • Liposarcoma: MDM2 amplification in well-diff/dediff types; often large, deep.
  • MRI for local staging; biopsy (core/incisional) confirms diagnosis.
  • Wide surgical excision with clear margins: primary treatment for sarcomas.
  • Desmoid tumors: Locally aggressive, high recurrence, do not metastasize.

Practice Questions: Soft Tissue Tumors

Test your understanding with these related questions

What is the best imaging modality for detecting early osteomyelitis?

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Flashcards: Soft Tissue Tumors

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Osteosarcomas present as a _____ enlarging mass or pathologic fractures

Hint: painful/painless

TAP TO REVEAL ANSWER

Osteosarcomas present as a _____ enlarging mass or pathologic fractures

painful

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