It is considered as a variant of pulmonary adenocarcinoma, accounting for about 5% of lung cancers. It is often multifocal, grossly appearing as a pneumonic consolidation. A characteristic feature is its growth along alveolar septa (lepidic growth pattern), without destroying the underlying alveolar architecture. Two subtypes are recognized: the cuboidal non-mucinous type and the mucinous type.
Cytologic diagnostic features (sputum and bronchial washing)
Small glandular clusters
Regular small cells with large cytoplasm
Nuclear hyperchromasia or vescicular nuclei with prominent nucleoli
Cytologic diagnostic features (FNA and bronchial brushing)
Monotonous cell population
Arrangements in cellular balls, sheets and papillae
The bronchioloalveolar carcinoma can be hardly distinguished from classic adenocarcinoma on cytologic preparations. Some cases may strictly resemble a papillary thyroid carcinoma, because of the presence of psammoma bodies, occasional nuclear grooves and pseudoinclusions, optically clear nuclei. Clinical history is helpful to exclude a metastasis.