Chest Imaging

Squamous cell carcinoma, pulmonary

a frequent type of bronchogenic carcinoma representing about one third of all lung cancers. Its association with cigarette smoking is very strong. Pathologically, these neoplasms often arise in the areas of squamous metaplasia commonly seen in the bronchial mucosa of cigarette smokers. They are centrally located involving the proximal bronchi and their growth is mainly endobronchial. Extension through the bronchial walls and along the bronchial mucosa may occur. Central necrosis is a frequent feature. Involvement of regional lymph nodes is common, occurring by direct extension or by means of lymphatic metastases. Histologically they include the formation of keratin pearls and intracellular bridges. Squamous cell carcinomas grow rapidly, but distant metastases occur relatively late. As a result, this type of lung cancer is associated with the best prognosis. Squamous cell carcinoma may be associated with hypercalcaemia due to ectopic parathormone production. It represents the most common cause of Pancoasts neoplasm. The radiological features of squamous cell carcinoma vary with the location of the tumour. When the tumour is central and endobronchial, it may produce a hilar or perihilar mass. Atelectasis or obstructive pneumonitis is usually present distal to the bronchial obstruction. When the lesion is small, bronchial wall abnormalities can be missed on standard radiography but are well depicted on CT scans. When the tumour is more peripheral (one third of cases) it manifests characteristically as a thick-walled cavitary mass with or without an airfluid level (Fig.1). Such a lesion may be indistinguishable radiographically from primary lung abscess. A solitary pulmonary nodule or mass is also a possible radiological manifestation.

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Fig.1

CT scan in a patient with a squamous cell carcinoma of the lung manifested by a cavitated mass in the left upper lobe.
Squamous cell carcinoma, pulmonary, Fig.1