Lecture Notes: Lung Imaging Abnormalities - Nodules and Masses

Overview

• Focus: Nodules and masses in lung imaging, specifically those that can be identified without additional testing.
• Categories:
  • Congenital entities
  • Neoplastic benign entity
  • Infectious entities
  • Inflammatory non-infectious entities

Types of Abnormalities

1. Non-Specific Nodules/Masses
   • Require further imaging or biopsy for diagnosis.
2. Specific Nodules/Masses
   • Have identifiable imaging features allowing for diagnosis from baseline imaging.

Principles of Specific Nodules/Masses

• Not all presentations are specific.
• Most nodules/masses are non-specific.
• Recognition based on pattern recognition, akin to "human machine learning."

Categories of Specific Masses

Congenital Entities

• Pulmonary AVMs
  • Creation of low-resistance pathways (absence of capillary bed).
  • Identified by tortuous vessels on CT.
  • Simple vs. complex (single or multiple feeding arteries).
• Pulmonary Sequestrations
  • Primitive lung not fully differentiated during development.
  • Infected sequestrations can appear as masses.
  • Intralobar: Within an existing lobe, systemic artery supply.
  • Extralobar: Outside of a lobe, own pleura envelope, systemic artery supply.
• Type 2 CPAMs
  • Overgrowth of blind bronchioles.
  • Bubbly mass, specific in upper lung regions.

Neoplastic Benign Entity

• Pulmonary Hamartomas
  • Well-circumscribed, may have macroscopic fat, sometimes with popcorn calcification.
  • Specific when fat or calcification is present, otherwise non-specific.

Infectious Entities

• Non-Invasive Aspergillosis
  • Fungus ball within pre-existing lung cavity.
• Invasive Aspergillosis
  • Affects immunocompromised, nodule/mass with ground glass halo.
  • "New moon" cavitation as immune system responds.
• Calcified Granulomas
  • Uniform or targetoid calcification indicative of granuloma.

Inflammatory Non-Infectious Entities

• Round Atelectasis
  • Scarring of visceral pleura contracts lung into a ball.
  • Associated with pleural scarring from asbestos, surgery, etc.
  • Appears as homogeneous mass with comet tail appearance.
• Lipoid Pneumonia
  • Foreign body reaction to lipid within lung parenchyma.
  • Can show macroscopic fat, specific when fat is present.

Summary

• Nine Specific Entities: Key to bypass algorithmic workup.
• Recognition of these entities allows for immediate diagnosis from baseline imaging without additional tests.
• Emphasizes importance of pattern recognition and knowledge of specific imaging features.