Atypical Adenomatous Lung Hyperplasia

**Semantic type:** Neoplastic Process

**Definition:** A preinvasive lesion in the lung. It is characterized by the presence of a small, localized proliferation of mildly to moderately atypical type II pneumocytes and/or Clara cells lining alveolar walls and sometimes respiratory bronchioles.

**Synonyms:** - AAH - Atypical Adenomatous Hyperplasia of Lung - Atypical Adenomatous Hyperplasia of the Lung - Atypical Alveolar Hyperplasia - Bronchioloalveolar Cell Adenoma