1. Endobronchial Metastases

Endobronchial metastases are most unusual. Melanoma and renal, colorectal and breast carcinomas are the primary tumours that most frequently give endobronchial submucosal metastases. In such cases the effect of airway obstruction is the dominant feature.

2. Miliary Metastases

Occasionally, innumerable tiny nodules closely resembling miliary tuberculosis are seen throughout both lungs, with no large masses and no evidence of lymphatic obstruction, such as is seen in lymphangitis carcinomatosa. Metastases are, however, one of the rarest causes of this pattern. The primary tumours that are most likely to produce miliary nodulation of the lungs are thyroid and renal carcinomas, bone sarcomas and choriocarcinoma.

3. Tumour Emboli

Radiologically recognisable pulmonary arterial hypertension may occur on rare occasions as a result of tumour emboli blocking small pulmonary arteries. Many tumours can embolise in this fashion, particularly hepatoma, carcinoma of the breast, kidney, stomach, and prostate and choriocarcinoma.

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