Know the signs: Many pulmonary conditions mimic lung cancer

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 - ground-glass opacification
78-year-old woman with adenocarcinoma in situ presenting as pure ground-glass opacification (diameter, 15 mm) on high-resolution CT image.
Source: Am. J. of Roentgenology doi: 10.2214/AJR.10.7262

A variety of pulmonary conditions are characterized by imaging findings that mimic lung cancers, making them difficult to differentiate from cancer, according to an article published in the October issue of the American Journal of Roentgenology.

To aid in diagnosis of pulmonary lesions, Kiyomi Furuya, MD, of National Hospital Organization Kyushu Medical Center in Fukuoka, Japan, and colleagues described the nature of a number of findings from these pulmonary conditions. They focused on ground-glass opacification (GGO) and solid nodules and masses as these two types of conditions are where the most clinical difficulty exists in differentiating benignity or malignancy.

Among the conditions described were:

Pure GGO: GGO is a hazy opacity that preserves underlying bronchial and vascular margins on high-resolution CT (HRCT), according to the authors. Pure GGO indicates the absence of solid components, and adenocarcinoma in situ shows pure GGO on HRCT. Differential diagnosis includes atypical adenomatous hyperplasia (AAH) and focal fibrosis. AAH is a putative precursor of adenocarcinoma that presents as a round or oval nodule usually smaller than 5 mm and without pleural indentation or vascular convergence. Furuya and colleagues noted it is indistinguishable from non-mucinous adenocarcinoma in situ.

Focal fibrosis is a benign non-neoplastic disease that often presents as a GGO with a round, polygonal, spiculated or ill-defined margins on HRCT.

Halo or Mixed GGO: The halo represents ground-glass opacity surrounding a nodule or mass, while mixed GGO is a nodule with both GGO and solid components. These patterns are seen in cases of non-neoplastic lesions with hemorrhagic nodules, and are difficult to distinguish from minimally invasive adenocarcinoma. “Careful attention to the patient’s clinical information will help in making the correct diagnosis.”

Lung Abscess: Lung abscess is often associated with bacterial pneumonia or preceded by aspiration, according to the authors, with aspiration occurring especially in patients with alcoholism, mental retardation, immune suppression or poor dental hygiene. They can present as lung masses or nodules that may be isolated or occur within areas of consolidation. Furuya and colleagues explained that in most cases, the walls of the cavities are smooth and less than 15 mm thick.

Hamartoma: This is a benign neoplasm that accounts for 6-8 percent of solitary lung tumors and 77 percent of all benign tumors, according to the authors. It is composed of mesenchymal tissues such as fat and calcification, with fat recognized on CT in about 60 percent of cases and calcification recognized in about 25 percent.

Other conditions that Furuya and colleagues indicated could be difficult to differentiate from lung cancer include pneumocytoma, focal organizing pneumonia, pulmonary amyloidosis and rounded atelectasis. “Awareness of these conditions with an understanding of their pathologic background and careful attention to the clinical information will help achieve correct diagnoses.”