What we can learn from the lepidic growth pattern of pulmonary metastases.

In lung adenocarcinoma, cancer cells can grow in a peculiar modality, replacing normal pneumocytes and creating glandular-like structures based on the alveolar architecture. This lepidic growth pattern is characterized by well differentiated epithelial cancer cells, that preserve their monolayer disposition, avoiding invasion of the interstitial space and dispersion into the airways. The same growth pattern can be assumed also by cancer cells originating from distant organs and a new interest has arisen around this modality of growth related to pulmonary metastases. Here we systematically reviewed the current literature about reports describing pulmonary metastases with a lepidic pattern and their clinical management. Although the small number of cases does not allow definitive conclusions about the frequency and clinical relevance, the existence of this peculiar manifestation reinforces the idea that metastatic disease is more complex and heterogeneous than is conveyed by the clinical guidelines.