IS Case 285: Squamous cell carcinoma with post-obstructive pneumonia
Imaging Sciences URMC 2009
Publication Date: 2009-08-05
The differential diagnosis for a cavitary lung lesion includes abscess, cavitated tumor (squamous cell carcinoma, sarcoma), cavitated granulomatous mass (aspergillus, tuberculosis, sarcoid), and cavitated post traumatic hematoma. The presence of a thick (>15mm) shaggy wall and eccentric cavitation are suggestive of malignancy.
Lung cancer is the leading cause of cancer death in the United States for both men and women, and is one of the most preventable forms. Tobacco use is considered responsible for 87% of lung cancer deaths. Besides smoking, other risk factors include exposure to radon, asbestos, arsenic, beryllium, and other carcinogens.
Non-small cell lung cancer (NSCLC), constitutes 80-85% of new cases of lung cancer in the United States. Frequent histologies include adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. Squamous cell carcinoma tends to occur centrally and is highly associated with a history of smoking. Histologically there is a pattern of infiltrating nests of malignant squamous cells with central necrosis, often resulting in central cavitation.
Symptoms resulting from the primary lung cancer depend on the location and size of the tumor. Cough is the most common symptom. Other symptoms include hemoptysis, bronchitis, bronchiectasis, and dyspnea. However, these symptoms are nonspecific and are commonly seen in smokers and people with chronic obstructive pulmonary disease (COPD). Wheezing is an uncommon presentation in lung cancer and may signify major airway obstruction, which can cause a post-obstructive pneumonia that fails to respond to standard therapy.
Lung cancer screening is considered controversial and is currently not recommended. Imaging evaluation may include radiography, CT, and PET. Radiography has limited value in the staging of lung cancer. Although it can detect pulmonary nodules as small as 3 to 4 mm, it is not reliable in detecting hilar or mediastinal lymphadenopathy. CT is commonly used to evaluate whether lung cancer is present in the hilar and mediastinal lymph nodes, liver, and adrenal glands, but its accuracy in identifying mediastinal lymph node involvement is suboptimal (sensitivity of 40 to 65% and specificity of 45 to 90%. Also, CT will miss small metastatic foci that do not result in mediastinal lymph node enlargement. PET is more sensitive than CT in staging lung cancer. It has a sensitivity of 83%, specificity of 96%, and negative predictive value of 96%. However, increased glucose metabolism also occurs with inflammatory processes. Obtaining both a PET and CT scan can enhance accuracy in the staging of lung cancer. PET also enhances detection of bone, liver, and adrenal metastases.
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