Multiple Pulmonary Nodules - DDx

General points:

    multiple pulmonary nodules >1cm diam (or when detected on CXR) are usually due to metastatic solid organ malignancy
multiple pulmonary nodules are more likely to be benign when < 1cm diam
in pts with a known malignancy, an nodule >0.5cm is more likely to be malignant than benign

 

Ddx:

 

malignancy:

· mets (from solid organ tumors) have a proclivity for lung bases as these are the best perfused segments of the lung--can also cause hemorrhage.

· Non-hodgkin's lymphoma can cause multiple pulmonary nodules.

· Kaposi's sarcoma can also present with mult pulm nodules, with a peribronchovascular distribution.

 

 

infectious:

· bacterial (abscesses) vs. septic emboli: Bacteremic pts can have multiple pulmonary abscesses (0.5-3cm diam, round, usually in lung bases).  Septic emboli can also result from bacteremia or R-sided endocarditis; these usually appear as 0/5-3cm round or wedge-shaped nodules with predeliction for peripheral areas of lower lobes. Atypical bacteria can also have a nodular “tree-in-bud” appearance

· fungal: histoplasmosis, cocci, crypto, invasive aspergillosis.  No clear predeliction for particular areas of the lung.  Invasive aspergillosis can present with "halo sign" due to local hemorrhage and cavitation.  Histo and cocci can occur in any host, depending on whether in an endemic area; invasive cryptococcal disease is typically seen in HIV + patient and invasive aspergillosis in immunocompromised hosts.

· mycobacterium: disseminated MAC (again usually seen in HIV+ or immunocompromised pts) and miliary TB

· parasites/flukes: paragonimus: a parasite endemic in parts of Asia--can migrate to pulmonary parenchyma; echinococcosis: pulmonary cysts produced by larval stage parasite, can be seen in association with livestock + dogs

· viral infections are less classically defined as “nodular”, but can appear as GGO, with tree-in-bud appearance (see below)

 

 

inflammatory/autoimmune:

· sarcoidosis

· Wegner's granulomatosis

· rheumatoid nodules

· lymphomatoid granulomatosis

· amyloidosis

· eosinophilic granulomas

· drug induced (ie. Methotrexate)

 

 

vascular:

· pulmonary AVMs (usually solitary, but can be multiple with associated wtih Weber-Osler-Rendu syndrome)

 

 

pneumoconioses:

· silicosis, coal worker’s pneumoconiosis etc.

· Usually in association with some fibrosis as well, nodules can range from 1-10cm diam and predominately in the upper lobes

· hamartomas (benign lung tumors)

 

 

Note: a “tree-in-bud” pattern is characterized by “small centrilobular nodules of soft-tissue attenuation, connected to multiple branching linear structures of similar caliber originating from a single stalk.” It is a common radiologic manifestation of infectious bronchiolitis and endobronchial spread of TB.  Can result from viral, bacterial or fungal infections. 

 

 

(Victoria Kelly MD, 5/14/11)