Preinvasive adenocarcinoma lesion of the lung
Preinvasive lesions for lung adenocarcinoma are a category of small non-invasive lung lesions which are closely related to adenocarcinoma of the lung. They may represent a spectrum of premalignant to low-grade malignant lesions.
The category includes two types of lesions:
- atypical adenomatous hyperplasia (AAH) - smaller, mild-moderate cellular atypia, without evidence of invasion
- adenocarcinoma in situ (AIS) - larger and with more atypia, although still without evidence of invasion
In 2011, the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society introduced a new classification and terminology for adenocarcinoma of the lung. In addition to retiring the term "bronchoalveolar carcinoma (BAC)", the 2011 update officially recognised "adenocarinoma in situ" as a distinct entity with excellent clinical prognosis.
Atypical adenomatous hyperplasia and adenocarcinoma in situ may be considered a spectrum of premalignant disease:
- atypical adenomatous hyperplasia is typically a small (≤5 mm) lesion with mild-moderate cellular atypia
- adenocarcinoma in situ lesions are larger, yet still ≤3 cm and demonstrating purely lepidic growth (no invasion)
Between these two, intermediate cases may be difficult to distinguish 1.
Findings which indicate more profound genetic alteration, such as non-lepidic (e.g. papillary) growth patterns or tumour necrosis, indicate a more advanced grade of disease.
Preinvasive lesions of adenocarcinoma are generally not evident by x-ray.
On CT, both atypical adenomatous hyperplasia and adenocarcinoma in situ typically manifest as a round, purely ground glass opacity.
- usually a single opacity 2
- multiple lesions more common with AIS 2
- "clear" periphery (>85%) 2
- lobuation, spiculation, pleural indentation are seen in both AAH and AIS, but less common (<21%)
- vacuole sign - internal gas-appearing lucency <5 mm
- specific to AIS in one 2017 radiology/pathology correlative study (n=80 lesions) 2
- 1. Travis WD, Brambilla E, Noguchi M et-al. International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma. J Thorac Oncol. 2011;6 (2): 244-85. doi:10.1097/JTO.0b013e318206a221 - Pubmed citation
- 2. Pan X, Yang X, Li J, Dong X, He J, Guan Y. Is a 5-mm diameter an appropriate cut-off value for the diagnosis of atypical adenomatous hyperplasia and adenocarcinoma in situ on chest computed tomography and pathological examination?. (2018) Journal of thoracic disease. 10 (Suppl 7): S790-S796. doi:10.21037/jtd.2017.12.124 - Pubmed