Cancers can metastasize to the lungs by several pathways. Most commonly, cancers spread to the lungs via pulmonary arteries or lymphatic channels. Less often, spread is by direct extension or endobronchial spread. Cancers that commonly metastasize to the lungs include: prostate, breast, renal, thyroid, testicle, gastrointestinal, melanoma, and sarcomas.
Radiograpically metastases tend to be multiple (95%). They are more often in the lung periphery and bases. Typically they have sharp margins. They can cavitate, particularly squamous cell carcinomas. Some may have calcifications.