Preinvasive adenocarcinoma lesion of the lung

Preinvasive lesions for lung adenocarcinoma are a typecategory of small noninvasive lung lesion which are closely related to adenocarcinoma of the lung. They may represent a spectrum of premalignant andto 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 nostill without evidence of invasion

Terminology

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.

Pathology

Atypical adenomatous hyperplasia and adenocarcinoma in situ may be considered a spectrum of premalignant disease, where atypical adenomatous hyperplasia is typically a small (<5≤5 mm) lesion with mild-moderate cellular atypia, while adenocarcinoma in situ lesions are larger, butyet still ≤3 cm and without evidence ofdemonstrating purely lepidic growth (no invasion). Indeed, intermediate cases may be difficult to distinguish ¹.

Findings which indicate more advancedprofound genetic alteration, such as non-lepidic (e.g. papillary) growth patterns or tumor necrosis, indicateindicatemore advanced grade of disease.

Radiographic features

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 higherround, purely ground glass opacity.