Tumor Microembolism and Lymphangitic Carcinomatosis

Pulmonary metastasis is common in the natural history of many malignancies. Although most metastases cause few symptoms, pulmonary tumor microembolism and lymphangitic carcinomatosis are exceptions. Both tumor microembolism and lymphangitic carcinomatosis are forms of microvascular metastasis involving the pulmonary blood vessels and lymphatic vessels, respectively that are pathologically distinct but closely related and often coexistent. These less common types of metastatic disease can dominate the clinical picture, causing profound respiratory impairment, potentially complicated by pulmonary hypertension and cor pulmonale, often in the absence of significant abnormalities on the chest radiograph. Antemortem diagnosis of both these disorders is frequently missed, usually because the diagnosis is not considered. Recognition of the characteristic perfusion scan pattern of “contour mapping” with both tumor microembolism and lymphangitic carcinomatosis, the distinctive high-resolution computed tomographic findings of lymphangitic carcinomatosis, and the advent of pulmonary microvascular cytology as a diagnostic modality are relatively recent advances that should lead to more frequent diagnosis, with the hope of improved outcome in selected patients. An illustrative case of tumor microembolism as the initial manifestation of cancer is presented, and the pathophysiology, clinical and imaging features, diagnosis, and treatment of tumor microembolism and lymphangitic carcinomatosis are reviewed.