Lipoid Pneumonia: HRCT and MRI Spectrum, Diagnostic Pitfalls, and Imaging-Based Diagnostic Workflow

Area of Science:

• Pulmonology
• Radiology
• Pathology

Background:

• Lipoid pneumonia (LP) is a rare pulmonary condition with diverse imaging features.
• Its varied presentation often leads to underdiagnosis and misdiagnosis as infectious, inflammatory, or neoplastic diseases.
• A standardized imaging-based diagnostic pathway for LP is currently lacking.

Purpose of the Study:

• To provide a structured, imaging-centered synthesis of lipoid pneumonia.
• To characterize the full spectrum of findings on high-resolution CT (HRCT) and MRI.
• To propose a pragmatic diagnostic workflow for LP.

Main Methods:

• A systematic literature search was conducted across major databases (PubMed, MEDLINE, Embase, Cochrane Library) from 1950 to 2025.
• Keywords included "lipoid pneumonia" and imaging terms like "HRCT," "computed tomography," and "MRI."
• Sixty studies were synthesized, supplemented by eight institutional cases with imaging-pathology correlation.

Main Results:

• HRCT is key, showing intralesional fat attenuation (-30 to -150 HU) in 40-80% of cases.
• Other HRCT findings include ground-glass opacity, crazy paving, nodules, and mass-like consolidation.
• MRI, especially chemical shift imaging, aids in equivocal cases; fat attenuation may be absent in up to 60% due to inflammation or fibrosis.

Conclusions:

• A pattern-based radiological approach using HRCT, clinical history, BAL cytology, and selective MRI is effective for diagnosing LP.
• This integrated strategy can prevent unnecessary invasive procedures, including surgical resection.
• Accurate diagnosis of lipoid pneumonia is achievable through a structured, imaging-guided workflow.