Mediastinal Pathology

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Mediastinal Anatomy - Compartment Command

Mediastinum: Central thorax. Classifications: Felson (CXR), ITMIG/IASLC (CT).

Felson's Compartments (Lateral CXR):

CompartmentBoundaries (Simplified)Key Contents
AnteriorSternum to pericardiumThymus, LNs, fat. (📌 "4 T's" masses: Thymoma, Teratoma, Thyroid, Lymphoma)
MiddleWithin pericardiumHeart, great vessels (SVC, Asc. Aorta, PA), trachea, bronchi, phrenic n.
PosteriorPericardium to vertebraeDesc. aorta, esophagus, thoracic duct, azygos v., nerves.

ITMIG Classification (CT-based): Prevascular, Visceral, Paravertebral compartments.

Mediastinal compartments on CT (ITMIG classification)

Exam Favourite: The anterior border of the middle mediastinum is the anterior aspect of the pericardium.

Anterior Mediastinum - Terrific T‑Time

📌 Mnemonic: The 5 Ts

Lesion (Age)Key Imaging FeaturesMarkers/Associations
Thymoma (Adults)Smooth, lobulated soft-tissue mass; calcification (10-30%)Myasthenia Gravis (MG) (30-50%), pure red cell aplasia (PRCA)
Teratoma/GCT (Young)Heterogeneous: fat, fluid, calcification (teeth), cysts↑AFP, ↑β-hCG (non-seminomatous GCTs)
Thyroid (Any age)Connects to neck; ↑attenuation (iodine) on NCCT; I-131 avidSubsternal goiter; ectopic tissue
(T) Lymphoma (Varies)Homogeneous lobulated mass/nodes; Hodgkin commonB-symptoms (fever, night sweats, weight loss)
Thoracic Aorta (Older)Aneurysm/dissection; aortic dilatation, mural thrombusAtherosclerosis, Marfan syndrome

Mediastinal masses by location and prevalence

Middle & Posterior Mediastinum - Central & Spinal Surprises

  • Middle Mediastinum:
    • Lymphadenopathy: Most common.
      • Causes: Lymphoma (bulky, discrete), TB (central necrosis, rim enhancement), Sarcoidosis (bilateral hilar/paratracheal, often symmetrical), Metastases.
    • Cysts: Well-defined, fluid density (0-20 HU), non-enhancing.
      • Bronchogenic: Near carina/main bronchi, most common congenital.
      • Pericardial: Right cardiophrenic angle typically.
      • Esophageal duplication: Posterior, may compress esophagus.
    • Vascular: Aortic aneurysm, dilated pulmonary artery (e.g., in pulmonary HTN).
  • Posterior Mediastinum:
    • Neurogenic Tumors: Most common primary posterior masses. Often round, sharp margins.
      • Schwannoma: Most frequent; possible cystic changes; "dumbbell" with neural foraminal extension.
      • Neurofibroma: Can be multiple in NF1.
      • Ganglioneuroma: Often larger, elongated.
    • Esophageal Pathology:
      • Tumors: Carcinoma (irregular thickening), leiomyoma (smooth submucosal).
      • Diverticula: E.g., epiphrenic (outpouching).
    • Paravertebral:
      • Extramedullary hematopoiesis: Lobulated masses in chronic anemia.
      • Infection/Abscess: E.g., TB spondylitis with paraspinal abscess.
    • Schwannoma with foraminal extension

⭐ Neurogenic tumors are the most common primary posterior mediastinal masses.

Acute Mediastinum - Alarming Air & Anger

Pneumomediastinum (Air)

  • Etiology: Spontaneous, Trauma (e.g., Boerhaave syndrome), Iatrogenic.
    • 📌 Mackler's Triad (Boerhaave): Vomiting, chest pain, subcutaneous emphysema.
  • Signs: Hamman's sign (crunch), subcutaneous emphysema.
  • Imaging:
    • X-ray: Continuous diaphragm sign, thymic sail sign (children), perivascular air.
    • CT: Confirms air.

⭐ Hamman's sign (mediastinal crunch) is a pathognomonic auscultatory finding in pneumomediastinum.

Mediastinitis (Anger)

  • Etiology: Esophageal perforation, Post-surgical (e.g., CABG), Descending necrotizing (oropharyngeal).
  • Clinical: Sepsis, chest pain.
  • Imaging (CT): Fluid collections, gas bubbles, fat stranding, abscess, effusions.

High‑Yield Points - ⚡ Biggest Takeaways

  • Anterior Mediastinum: Remember the 4 T's (Thymoma, Teratoma, Thyroid, Terrible Lymphoma).
  • Thymoma: Most common primary anterior tumor; strong link to Myasthenia Gravis.
  • Teratoma: Common GCT; shows fat, fluid, calcification.
  • Middle Mediastinum: Think lymphadenopathy (lymphoma, sarcoidosis) and developmental cysts.
  • Posterior Mediastinum: Neurogenic tumors (schwannoma) are most frequent.
  • Hodgkin's Lymphoma: Often presents with contiguous mediastinal lymphadenopathy.
  • Sarcoidosis: Classic bilateral hilar and right paratracheal lymphadenopathy.

Practice Questions: Mediastinal Pathology

Test your understanding with these related questions

Anterior Mediastinal nodes are included in which level of lymph nodes?

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Flashcards: Mediastinal Pathology

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_____ is the investigation of choice for evaluation and diagnosis of bronchogenic carcinoma.

TAP TO REVEAL ANSWER

_____ is the investigation of choice for evaluation and diagnosis of bronchogenic carcinoma.

CT

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