Random (Miliary) Distribution, Centrilobular Nodules
Eric J. Stern, MD
DIFFERENTIAL DIAGNOSIS
Common
Metastases, Hematogenous
Metastases, Miliary
Infection, Miliary
Mycobacterial
Fungal
Viral
Less Common
Infectious Bronchiolitis
Sarcoidosis
Hypersensitivity Pneumonitis
Rare but Important
Talcosis, Intravenous
Vasculitis
Langerhans Cell Granulomatosis
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Random pattern
Nodules are diffuse and not clustered into rosettes (like grapes)
Feeding vessels to nodules helpful clue to random pattern
Blood flow to lung position is gravitationally dependent: Increased in bases in upright position, dorsal lung in supine position
Random pattern often more severe in lower lung zones and periphery
Random vs. bronchovascular pattern
Bronchovascular centrilobular nodules clustered into rosettes
Bronchovascular pattern may have signs of small airways obstruction (mosaic attenuation, tree-in-bud opacities, bronchiectasis, air-trapping)
Random vs. lymphatic pattern
Lymphatic centrilobular nodules clustered like grapes
Lymphatic nodules more profuse along pleura and fissures
Lymphatic nodules may be arranged in rays along blood vessels and airways
Lymphatic pattern often more severe in upper lung zones; random pattern often more severe in lower lung zones
Helpful Clues for Common Diagnoses
Metastases, Hematogenous
Shape and margin characteristics
Round, sharply defined margins (40%), irregular shape, sharply defined (15%), round, ill-defined margins (15%), irregular shape, ill-defined margins (30%)
Variable size: Due to multiple episodes of primary tumor dissemination
Typically solid: Adenocarcinomas from gastrointestinal malignancies, lung, breast, melanoma, sarcoma
May be cavitary: Squamous cell carcinomas from primary head and neck, cervical, adenocarcinoma
May be calcified
Psammomatous calcification: Mucin-producing adenocarcinomas, such as from colon, ovary
Treated neoplasms: Thyroid, adenocarcinomas
Ossified metastases: Chondrosarcoma and osteosarcoma
May be surrounded by ground-glass halo
Vascular tumors with hemorrhage: Choriocarcinoma, angiosarcoma, renal cell carcinoma
Metastases, Miliary
Tumors whose primary venous drainage is to lungs
Medullary thyroid carcinoma, renal cell carcinoma, head and neck tumors, ovarian or testicular tumors, melanoma
Nodules similar in size, too numerous to count
Infection, Miliary
Nearly any organism, most commonly Mycobacterium tuberculosis, fungal, viral
Miliary tuberculosis
Disseminated disease in either primary or post-primary infection
Immunosuppressed patients most susceptible, especially those with impaired cellular immunity
Chronic miliary tuberculosis: Miliary nodules often larger in upper lung zones
Miliary histoplasmosis
Dissemination usually due to reactivation of latent disease
In AIDS patients, dissemination usually when CD4 count is < 75 cells/mm3, associated hilar and mediastinal lymphadenopathy
Associated with adrenal insufficiency
Miliary blastomycosis
Chronic miliary nodules: Often larger in upper lung zones
Disseminated disease may occur up to 3 years after primary infection
Extrathoracic involvement: Skin, bone, prostate, central nervous system
Pneumonia, viral
Diffuse, often ill-defined nodules
Nodules may coalesce or have ground-glass halos
Helpful Clues for Less Common Diagnoses
Infectious Bronchiolitis
Typical bronchovascular pattern
Fever, elevated white blood cell count
Typical pattern in tree-in-bud opacities
Patchy or diffuse
Sarcoidosis
Typical lymphatic distribution
Nodules with heterogeneous distribution, cut swath through lung
May have symmetric hilar and mediastinal adenopathy
Nodules more profuse in upper lung zones
Hypersensitivity Pneumonitis
Acute or subacute
Typical bronchovascular pattern
Centrilobular ground-glass nodules + lobular air-trapping
Environmental history important
Helpful Clues for Rare Diagnoses
Talcosis, Intravenous
Found in illicit drug abuse
Talc common filler in oral medications, not meant to be injected intravenously
Nodules often pinpoint in size and may be of higher density
Nodules more profuse in mid and lower lung
In contrast, inhalational talcosis more common in upper lung zones
May result in progressive massive fibrosis
Vasculitis
Centrilobular nodules from hemorrhage or hemosiderin deposits (often bronchovascular distribution with larger vessel involvement)
Often nodules follow episodes of hemorrhage (diffuse or patchy ground-glass opacities and consolidation)
Sedimentation rate usually elevated
Langerhans Cell Granulomatosis
Typical bronchovascular pattern
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