CT imaging features of thin-walled cavitary squamous cell lung cancer

Primary lung cancer manifesting as a thin-walled solitary cavity, occurs relatively infrequently. The most common histologic type presenting such a pattern is squamous cell cancer, followed by adenocarcinoma, and finally - large cell cancer. Cavitation is typically not seen in small cell lung cancer. Entities indicating malignancy of such lesions include irregular cystic wall, wall nodule formation, nodular septa or increased standard uptake on positron emission tomography (PET). We are presenting a case of a squamous cell lung cancer manifesting on chest CT as a thin-walled septated cavity with irregular margins mimicking a cyst. The lesion was reported unchanged in a follow-up computed tomography after 3 months. A follow-up scan obtained 2 years after initial examination showed thickening of a cyst wall, solid structures within its lumen and thoracic lymph nodes enlargement.