Thoracic Imaging 2003 - Society of Thoracic Radiology
Thoracic Imaging 2003 - Society of Thoracic Radiology
Thoracic Imaging 2003 - Society of Thoracic Radiology
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Unusual Manifestations <strong>of</strong> Lung Cancer<br />
Michelle S. Ginsberg, M.D.<br />
Objective<br />
The common cell types <strong>of</strong> lung cancer have certain typical<br />
radiographic appearances which will be briefly discussed.<br />
However it is important to be familiar with the more unusual<br />
presentations as well. The purpose <strong>of</strong> this review is to suggest<br />
the correct diagnosis <strong>of</strong> bronchogenic carcinoma when the radiographic<br />
manifestations <strong>of</strong> a particular tumor are rare, mimic<br />
benign disease, or suggest disease <strong>of</strong> organs other than the lung.<br />
The appearance <strong>of</strong> missed lung cancer, and means <strong>of</strong> improving<br />
detection <strong>of</strong> these lesion will also be discussed.<br />
Adenocarcinoma<br />
Adenocarcinoma is the most common cell type <strong>of</strong> bronchogenic<br />
carcinoma and accounts for approximately 50% <strong>of</strong><br />
cases. CT usually demonstrates a solitary peripheral pulmonary<br />
nodule. The nodule may be smooth or spiculated. Hilar and<br />
mediastinal lymph node involvement and distant metastases are<br />
frequently present at the time <strong>of</strong> diagnosis. Peripheral tumors<br />
may directly invade the pleura and grow circumferentially<br />
around the lung and mimic diffuse malignant mesothelioma. 1<br />
Central tumors may directly invade mediastinal structures or via<br />
the pulmonary veins invade the left atrium.<br />
Bronchioloalveolar carcinoma<br />
Bronchioloalveolar carcinoma is considered a subtype <strong>of</strong><br />
adenocarcinoma and commonly presents as a solitary nodule. 2<br />
There may also be surrounding ground glass opacity. Cavitation<br />
an infrequent finding in adenocarcinoma may be seen in bronchioloalveolar<br />
carcinoma. 3 Although less common, consolidation<br />
and multiple small pulmonary nodules are other forms <strong>of</strong><br />
presentations. 3 High-resolution CT may demonstrate air attenuation<br />
and pseudocavitation within the nodules corresponding to<br />
small bronchi and cystic spaces. 4 Unusual radiographic appearances<br />
include lobar atelectasis, expansile consolidation without<br />
air bronchograms, or elongated lobulated opacity resembling<br />
mucoid impaction. 5,6<br />
Squamous cell carcinoma<br />
Squamous cell carcinoma most <strong>of</strong>ten presents as a central<br />
endobronchial obstructing lesion with associated atelectasis or<br />
post obstructive pneumonia. Less commonly approximately a<br />
third <strong>of</strong> these tumors may present as a solitary peripheral nodule<br />
with or without cavitation. 7 When the tumor cavitates, the inner<br />
wall is typically thick and irregular, and if secondarily infected<br />
may develop an air fluid level.<br />
Undifferentiated large cell carcinoma<br />
Undifferentiated large cell carcinoma usually presents as a<br />
large peripheral lesion, although a smaller proportion may also<br />
be centrally located. These tumors grow rapidly and metastasize<br />
early <strong>of</strong>ten presenting with hilar or mediastinal adnopathy.<br />
Giant-cell carcinoma is a subtype with multiple giant cells and a<br />
more aggressive behavior and poorer prognosis.<br />
Multiple primary carcinomas<br />
Synchronous lesions are defined as the presence <strong>of</strong> two<br />
tumors at the time <strong>of</strong> or closely following initial diagnosis. The<br />
incidence <strong>of</strong> synchronous multiple primary tumors is less than<br />
3.5% <strong>of</strong> all lung cancer patients. 9 This number may even be<br />
higher depending on the cell type and how carefully further primary<br />
tumors are sought as well as the rigidity <strong>of</strong> the criteria<br />
used to define the tumors as primary lesions. Difference in cell<br />
type is an accepted criteria, however tumors <strong>of</strong> the same histologic<br />
type must be physically quite separate as well as separated<br />
by noncancerous lung tissue. 9,10<br />
Metachronous lesions are defined as the second cancer<br />
appearing after a time interval, usually 12 months or more.<br />
These lesions compromise at least two thirds <strong>of</strong> multiple pulmonary<br />
neoplasms, and on average are recognized 4 to 5 years<br />
after the first primary. 10%-32% <strong>of</strong> patients surviving resection<br />
for lung cancer may develop a second primary tumor. 9 These<br />
lesions are regarded as multiple primary lesions only if they<br />
show unique histologic features. Squamous cell cancer is the<br />
most common histologic type <strong>of</strong> multiple carcinomas.<br />
Metastases<br />
The adrenal glands are one <strong>of</strong> the most common sites <strong>of</strong><br />
metastases from lung cancer ranging from 5-10% <strong>of</strong> the time at<br />
presentation. In our experience we have also seen two cases <strong>of</strong> a<br />
mass within the adrenal gland that represented a collision tumor<br />
consistent <strong>of</strong> contiguous adrenal adenoma and metastasis.<br />
Lung cancer may present with unusual sites <strong>of</strong> metastases.<br />
For example the gallbladder an unusual site <strong>of</strong> metastatic disease<br />
in general can be the site <strong>of</strong> a lung metastasis.<br />
The kidneys, pancreas and small bowel may also be sites <strong>of</strong><br />
metastases and may be radiographically indistinguishable from<br />
a primary tumor <strong>of</strong> that organ. Serosal and mesenteric implants<br />
may become quite large. Invasion with perforation <strong>of</strong> the adjacent<br />
bowl may result in a large mass with air within it having an<br />
appearance indistinguishable from an abscess.<br />
Muscle and subcutaneous tissues are other infrequent sites <strong>of</strong><br />
metastases from bronchogenic cancer.<br />
Missed lung cancer<br />
A missed lung cancer is unusual by virtue <strong>of</strong> the fact that it<br />
was not detected. In contrast, most usual ones are detected<br />
when in "easy" areas <strong>of</strong> lungs on a chest radiograph or CT.<br />
Potentially resectable NSCLC lesions missed at chest radiography<br />
were characterized by predominantly peripheral (85%) and<br />
upper lobe (72%) locations and by apical and posterior segmental/subsegmental<br />
locations in an upper lobe (60%). The missed<br />
cancers had a median diameter <strong>of</strong> 1.9 cm. Most <strong>of</strong> these missed<br />
lesions (98%) were obscured by anatomic structures on the<br />
chest radiograph, most <strong>of</strong>ten by bones (ribs and clavicle). Only<br />
the lateral radiograph revealed the cancer retrospectively in 5%<br />
<strong>of</strong> patients. 11<br />
Although chest CT is more sensitive for the detection <strong>of</strong> lung<br />
nodules than chest radiographs, the potential for missing small<br />
lung cancers at CT exists. A recent study by Li et al. evaluated<br />
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