CT Findings of Atypical Adenomatous Hyperplasia in the Lung

CT Findings of Atypical Adenomatous Hyperplasia in the LungObjective: The aim of this study was to analyze the computed tomographic (CT) findings of atypical adenomatous hyperplasia (AAH) in the lung. Materials and Methods:The CT findings of AAHs in eight patients were retrospectively reviewed.The CT findings of each AAH lesion were evaluated for multiplicity, location, shape, size and internal density of the lesion, the interface between the normal lung and the lesion, the internal features within the lesion and any change of the lesion on the follow-up CT scans (range: 33 to 540 days; average: 145.3 days). Results:The eight patients consisted of three men and five women (age range: 43 71 years).Six of eight patients were asymptomatic.Four of them (50%) had synchronous malignancies in the lung: adenocarcinoma of the lung (n = 3), and metastatic squamous cell carcinoma from the uterus (n = 1).We could identify and evaluate eleven AAH nodules in seven patients on the CT scans.Three patients had multiple AAHs.Seven of the 11 lesions (64%) were located in the upper lobe.All the AAHs showed a well-defined oval or round shape and pure ground-glass opacity (GGO) without any solid component (size: 3.9 3 mm to 19 17 mm; internal attenuation: 467 to 785 HU).All the AAHs showed no change of their size and internal density on the follow-up CT scans.Conclusion: Atypical adenomatous hyperplasia is often associated with malignancy.This tumor is shown on CT as persistent well-defined oval or round nodular GGOs without solid components, and it does not change on the follow-up CT.typical adenomatous hyperplasia of the lung (AAH) is defined as a peripheral focal proliferation of atypical cuboidal or columnar epitheial cells along the alveoli and respiratory bronchioles (1).Its morphological similarity and recent molecular biological analysis have suggested that AAH could be a precursor lesion or even an early lesion of well-differentiated adenocarcinoma of the peripheral lung (2 6).In past, the AAH that could not be detected on the radiologic examinations before surgery was discovered incidentally in the surgically resected specimens from lung cancer patients, and this lesion was predominantly seen in adenocarcinoma patients (7).However, the number of radiologically detected AAH lesions has been increasing in Japan due to the wide-spread use of CT in clinical practice and also because of the mass screening for early lung cancer (8).Since mass screening for early lung cancer using CT is prevalent in other countries, including Korea, the radiologically detected AAH will increase dramatically as it did in Japan.To the best of our knowledge, some investigators have reported the radiologic and clinical features or the pathologic characteristics of AAH, but there are few reports in the radiologic literature that give a comprehensive assessment about AAH in the