Rare growth pattern of a solitary cystic lung metastasis from colon cancer: a case report.

An 82-year-old male, who had undergone sigmoid colon cancer surgery (at the age of 78 years) and primary lung cancer surgery (at the age of 81 years), was found to have a cavitating lesion in the left lower lobe on chest computed tomography (CT). A chest CT that had been performed just before the primary lung cancer surgery revealed a small thin-walled cyst at the same site at which the cavity was detected in the current CT. Bronchoscopic examination revealed no evidence of malignancy. A follow-up chest CT performed 5 months later revealed that the lesion had grown and that the cyst contained a well-defined lobular nodule. Video-assisted thoracoscopic left basal segmentectomy was performed. The histopathological diagnosis was metastasis from colon cancer. We report this unusual case in which a pulmonary metastasis changed over time from a cystic lesion to a nodular lesion.