The prominent linear markings seen grossly and radiographically in this lung result from lymphangitic spread of metastatic carcinoma, also known as pulmonary lymphangitic carcinomatosis (PLC). In this pattern of metastases, the carcinoma spreads mainly along lymphatic channels that accompany the bronchovascular bundles in the septae between lung lobules. Besides the linear or reticular interstitial markings, more marked axially than peripherally, seen here on the chest CT scan in lung window, more subtle involvement may appear on a chest radiograph as Kerley's B lines. Patients may have cough and dyspnea. Though best known as a pattern of metastases for prostate and breast carcinomas, PLC can potentially occur with a wide variety of primary sites.