Fig. 12.8 Pulmonary Paragonimus westermani (PW) infestation in a 46-year-old man proved by sputum smear showing parasitic eggs and positive ELISA test for PW. (a, b) Lung window images of consecutive CT (2.5-mm section thickness) scans obtained at levels of right

bronchus intermedius show multiple nodules with (open arrows) or without (arrows) internal cavity. (c) Coronal reformatted image (2.0- mm section thickness) demonstrates multiple cavitating (open arrows) and noncavitating (arrows) nodules in both lungs

Lung Squamous Cell Carcinoma

as a Cavitary Lesion

Pathology and Pathogenesis

Squamous cell carcinoma (SCC) is a malignant epithelial tumor showing keratinization or intercellular bridges that arise from bronchial epithelium. Two-thirds of SCCs are centrally located, arising from proximal bronchi, and onethird of cases are peripherally located (Fig. 12.1). Tumors are Þrm gray-white masses with areas of necrosis and cavitation, and central lesions often have endobronchial growth, which may occlude the lumen of airways and cause obstructive changes. Tumor cells are polygonal and hyperchromatic and have irregular nuclei and prominent nucleoli; the amount of cytoplasm is variable from abundant to scanty. There are several histologic variants as follows: papillary variant, clear-cell variant, small-cell variant, basaloid variant, and alveolar space-Þlling type of peripheral SCC [15].

Symptoms and Signs

Hemoptysis is an important feature of SCC of the lung that can be related both to central airway location of the tumor and to an increased propensity to cavitation [16]. Shortness of breath and fever occur due to atelectasis and postobstructive pneumonia. In general, it tends to be locally aggressive with less frequent metastasis to distant organ than adenocarcinoma of the lung. Chest wall invasion causes chest pain. Hypercalcemia may be present as a paraneoplastic syndrome secondary to secretion of parathyroid hormone-related protein.

CT Findings

The most common radiologic abnormality of SCC is a large central mass and atelectasis secondary to the airway obstruction [17]. One-third of SCCs present as intraparenchymal nodules or masses that lack apparent connection to a bronchus (Fig. 12.1). There has been a more recent shift, however,