Objective: The purpose of this study was to use serial CT observations to characterize early-stage lung cancer in patients with chronic interstitial pneumonia.
Materials and methods: We found 23 lung cancers in 22 patients during routine follow-up of chronic interstitial pneumonia between 1999 and 2010. Patients with lung cancer found at initial CT were excluded. Two radiologists independently reviewed serial CT scans, determined the earliest scan showing lung cancer, and evaluated the tumor shape, size, density, and location. Delay in diagnosis was measured from the time of the earliest scan showing lung cancer and the subsequent clinical diagnosis.
Results: During the mean follow-up period of 4.1 years, CT scans were obtained eight times on average. The median tumor size at presentation was 11 mm, and at clinical diagnosis was 22 mm. The median delay in diagnosis was 409 days. Fifteen tumors (65.2%) were in the interface between normal and fibrotic lung cysts (honeycomb cysts, paraseptal emphysema, and traction bronchiolectasis), four were in the area of ground-glass opacity, and one was in the midst of honeycomb cysts. Twelve tumors were round or oval, eight tumors had an ill-defined stellate shape, and two had a bandlike shape. One tumor appeared as an area of ill-defined increased lung attenuation.
Conclusion: Nearly one half of the tumors had a stellate or bandlike shape and were difficult to recognize as tumors initially. Most of the tumors were located at the interface between normal lung and fibrotic cysts; only rarely were tumors located in the midst of honeycomb cysts.