Random micronodules are small, round opacities less than 3 mm in
diameter that are scattered throughout the lung parenchyma
without a specific pattern or distribution. Unlike centrilobular or
perilymphatic micronodules, which follow the bronchioles or
lymphatic pathways, random micronodules are dispersed
irregularly, suggesting a hematogenous spread of disease. This
pattern is often associated with conditions like miliary tuberculosis,
fungal infections (such as histoplasmosis or cryptococcosis),
metastatic cancer (especially from primary sites like the thyroid or
kidneys), and pneumoconioses (e.g., silicosis). The pathogenesis
involves the spread of infectious agents, tumor cells, or inhaled
particles through the bloodstream or lymphatic system, leading to
the formation of these nodules. Diagnosis relies on high-resolution
CT (HRCT) scans, where random micronodules appear as
numerous, uniformly scattered spots, and further clinical
evaluation, including sputum analysis, biopsy, or blood tests, may
be necessary to identify the underlying cause.