Rapidly growing small peripheral lung cancers detected by screening CT: correlation between radiological appearance and pathological features

12 peripheral small lung cancers (<20 mm) of rapid growth (volume doubling time <150 days), detected by repeated low dose CT screening, were evaluated to examine their CT features and to correlate such features with histopath ological findings. Each patient's CT images, including follow-up and thin s ection CT images, were studied retrospectively to determine tumour growth r ate and CT morphological features. Nine of the tumours exhibited a solid tu mour growth pattern: seven of these showed a well defined, homogeneous, sof t tissue density with spicular or lobulated margin. These seven tumours inc luded small cell lung cancer (n = 3), moderately differentiated adenocarcin oma (n = 2), poorly differentiated adenocarcinoma (n = 1) and squamous cell carcinoma (n = 1). The other two tumours, a moderately differentiated aden ocarcinoma and a well differentiated adenocarcinoma, appeared as irregular, soft tissue density nodules with poorly defined margins. The latter exhibi ted an air bronchogram pattern and a small cavity. The remaining three tumo urs exhibited a lepidic tumour growth pattern. They showed ground glass opa city or ground glass opacity with a higher density central zone on CT image s and were well differentiated adenocarcinomas. Tn conclusion, most periphe ral small lung cancers of rapid growth were adenocarcinomas. They also incl uded small cell lung cancer and squamous cell carcinoma. The majority showe d solid tumour growth pattern and lacked an air bronchogram and/or small ai r spaces in the nodule. Some well differentiated adenocarcinomas with lepid ic tumour growth pattern also showed rapid growth.