Preinvasive adenocarcinoma lesion of the lung
Preinvasive lesions for lung adenocarcinoma are a type of small noninvasive lung lesion which are closely related to adenocarcinoma of the lung. They may represent a spectrum of premalignant and low-grade malignant lesions.
The category includes two types of lesions:
- atypical adenomatous hyperplasia (AAH) - smaller, mild-moderate cellular atypia
- adenocarcinoma in situ (AIS) - larger and with more atypia, although no evidence of invasion
In 2011, the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS) introduced a new classification and terminology for adenocarcinoma of the lung. In addition to retiring the term "bronchoalveolar carcinoma (BAC)", the 2011 update officially recognized "adenocarinoma in situ" as a distinct entity with excellent clinical prognosis.
Given its relatively recent recognition, adenocarcinoma in situ remains somewhat controversial and is variable regarded as a low-grade malignancy.
Atypical adenomatous hyperplasia and adenocarcinoma in situ may be considered a spectrum of premalignant disease, where atypical adenomatous hyperplasia is typically a small (<5 mm) lesion with mild-moderate cellular atypia, while adenocarcinoma in situ lesions are larger, but still ≤3 cm and without evidence of invasion. Indeed, intermediate cases may be difficult to distinguish 1.
Findings which indicate more advanced genetic alteration, such as non-lepidic (e.g. papillary) growth patterns or tumor necrosis, indicate a higher