The spread of lung cancer to the brain

The existence of a lymphatic drainage for the brain is disputed. In consequence, the current view is that lung cancer metastasises to this organ via the arteries.

Theoretically, arterial scattering of tumour emboli should result in an even distribution of deposits on either side of the brain. Similarly, lymphogenous dissemination to the brain would lead to ipsilateral preponderance of deposits.

Two hundred and fifty cases of brain metastases following lung cancer are analysed. The cases in the series are those in which metastases occurred either wholly or mainly in one cerebral or cerebellar hemisphere.

It is found that the metastatic trend is ipsilateral rather than even. A statistically significant result was obtained, for there were 143 growths which were wholly or mainly ipsilateral as against 107 contralateral ones.

Fifty-five cases collected from the literature also exhibited a statistically significant ipsilateral preponderance. Five cases illustrative of this trend in metastasis are appended.

Corroborative evidence is adduced from the literature:

• 1.

  Supradiaphragmatic tumours metastasise to the brain more often than infradiaphragmatic growths.

• 2.

  The relatively nearer cerebellum is a site of metastatic predilection.

• 3.

  Multiple macroscopic metastases occur only twice as often as the solitary.

• 4.

  The histopathology of metastatic brain tumours points to the importance of perivascular and subarachnoid spaces.

It is concluded that a unitary theory of metastasis to both the lymph nodes and organs like the brain and adrenal is possible and may be of fundamental importance.