The diagnosis is: (e) metastatic lung disease

The chest x-ray (conventional chest radiography [CXR] Figure 1) reveals numerous small irregular pulmonary nodules bilaterally, measuring less than 2 cm each, with elevation of the right hemidiaphragm and a small right pleural effusion, along with mild fullness to the right hilum, suggesting local adenopathy. The heart size is normal. A computerized tomography (CT) scan of the thorax and abdomen (not shown) confirmed the above findings, and noted no evidence of liver metastases. That would be extremely unusual for colon cancer, since the venous drainage is through the portal vein into the liver, and liver metastases are typically present prior to distant mets. However, rectal carcinoma acts differently as there is a dual venous drainage supply in that area (portal venous and systemic). As such, distant mets may develop in lieu of liver lesions and for that reason, surveillance for lung metastases should continue for a longer period than for colon cancer (proximal to rectum). Lung metastases typically develop within 3 years of diagnosis; however, delayed cases have been reported with metastases from the rectal primary developing up to 15-20 years later — although in many of those, local recurrence has also occurred.

Congestive heart failure (CHF) will reveal streaky increased linear interstitial lung markings (with thin peripheral horizontal septal lines known as ‘Kerley B lines’) and patchy air space changes, from the pulmonary edema present. The heart size is usually enlarged and bilateral pleural effusions are often present. CHF with pulmonary edema doesn’t present as multiple pulmonary nodules.

Interstitial pneumonias are often bilateral and can demonstrate a reticulo-nodular appearance, although the nodules are usually small and uniform, measuring 1-2 mm in size, not 1-2 cm.

Stage II sarcoidosis involves central and hilar adenopathy as well as lung disease. The lung disease may be seen as nodular, increased interstitial changes or frank airspace disease. As with interstitial pneumonia, the nodules in sarcoidosis are typically smaller, in the range of 1-3 mm although larger more irregular nodules can occur. Age of onset of sarcoidosis is usually between 20 and 40 years.

Histoplasmosis is a benign fungal granulomatous disease (agent Histoplasma capsulatum) endemic in certain river regions such as the Mississippi and Ohio River valleys and along the St. Laurence River in Ontario. The patients generally suffer non-specific flu-like symptoms initially (or no symptoms at all), then develop multiple lung nodules and central adenopathy months to years later. These nodules often calcify centrally, confirming their benign nature on imaging studies. Calcified granulomas are often seen in the liver and spleen as well. The diagnoses of Stage II sarcoid or histoplasmosis are both certainly possibilities in this patient but it’s statistically more likely that multiple lung metastases would be the cause of the CXR appearance.

References:

• Sadahiro S et al. Japanese J of Clin Oncol 2005;35(1):18-22.
• Jin GY et al. Am J of Roengtenol 2004;183:1013-20.
• Wormanns D, Diederich S. European Radiol 2004;14(8):1380-91.