What is an organized hematoma?

Organized Hematoma: Definition and Clinical Significance

An organized hematoma is a chronic state of blood collection that has developed a fibrous capsule, containing central blood products surrounded by granulation tissue and dense fibrous tissue at the periphery, which may simulate neoplasms and can progressively expand over time. 1

Pathophysiology and Development

Organized hematomas develop through a specific process:

1. Initial Formation: Begins as a conventional hematoma following trauma, surgery, or spontaneous bleeding
2. Organization Process: Instead of normal resolution, the hematoma undergoes:
   • Development of a pseudocapsule/fibrous wall
   • Formation of granulation tissue
   • Fibrotic changes at the periphery 2, 3
3. Expansion Mechanism: The capsule prevents normal resorption while allowing continued intracapsular bleeding, leading to progressive growth 3

Characteristic Features

• Temporal Pattern: Slow, progressive growth over weeks to years after the initial bleeding event 2
• Imaging Appearance: Often enhancing mass lesions that can mimic neoplasms 4
• Histology: Three distinct layers:
  • Central mass of blood/blood products
  • Middle layer of granulation tissue
  • Peripheral dense fibrous tissue/capsule 1

Anatomical Locations

Organized hematomas can occur in various locations:

• Soft tissues (including thigh, neck) 2, 3
• Paranasal sinuses (particularly maxillary sinus) 1, 5
• Brain (especially following gamma knife radiosurgery for AVMs) 4
• Parapharyngeal space 1
• Adrenal gland 1
• Lung 1

Clinical Presentation

• Symptoms: Progressive mass effect causing:
  • Pain and swelling in affected area
  • Neurological symptoms when intracranial (headache, hemiparesis) 4
  • Compression of adjacent structures
• Physical Findings: Slow-growing mass that may be mistaken for malignancy 2

Diagnosis

• Imaging:

  • MRI: Shows heterogeneous signal intensity with peripheral enhancement
  • CT: May demonstrate an encapsulated mass with varying density 5
  • Both modalities often suggest neoplasm as differential diagnosis

• Differential Diagnosis:

  • Primary or metastatic tumors
  • Vascular malformations
  • Abscesses
  • Cysts with hemorrhagic components

Management

• Surgical Excision: Complete removal of the hematoma including the capsule is the treatment of choice for symptomatic lesions 4
• Partial Removal Risks: Incomplete removal may lead to continued expansion or recurrence 4
• Outcomes: Generally good with complete surgical excision

Clinical Pearls

• Organized hematomas may develop years after the initial bleeding event (up to 64 years reported) 2
• They can occur without obvious trauma history or in patients with bleeding tendencies 1
• These lesions should be considered in the differential diagnosis of slow-growing masses, especially with history of trauma or bleeding disorder
• Steroid treatment is typically ineffective for organized hematomas 4

Specific Contexts

• Post-Radiosurgery: Can develop 2-12 years after gamma knife radiosurgery for cerebral AVMs, even after complete AVM obliteration 4
• Pediatric Cases: Rare cause of neck swelling in children that can mimic neoplasms 3
• Maxillary Sinus: Sometimes called "blood boil" in Japan due to encapsulated blood and locally aggressive behavior 5

Understanding organized hematomas is important for proper diagnosis and management, as they can mimic malignancies but have a completely different treatment approach and prognosis.