Bronchioloalveolar carcinoma

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
• Clean background

Cytologic diagnostic features (FNA and bronchial brushing)

• Monotonous cell population
• Arrangements in cellular balls, sheets and papillae
• Clean background

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.

Immunocytochemistry

• Cytokeratin 7 +
• Cytokeratin 5 –
• Cytokeratin 20 –
• Neuroendocrine markers +-
• TTF-1 +

	FNA of BAC - TTF-1