Halsted's theory

Halsted proposed that breast cancer cells spread from the primary tumour to the first node in the lymphatic chain. At this point they were impeded by a filtering mechanism. Once the first node was overwhelmed with local deposit, only then could the tumour pass onwards to the next lymph node in the regional chain. Consequently, Halsted deemed that radical resection of all the regional lymphatic drainage was necessary for complete eradication of the tumour.

In support of this theory:

• clinically, the natural history of most breast cancer seems to involve a sequential progression of involvement of the nodes along a regional chain
• in a large minority, radical resection of regional lymphatics in women with axillary node disease does seem to prevent recurrence
• tumour emboli - the basis of the alternative theory - have not been demonstrated in the clinical setting

However, against Halsted's theory are:

• radical surgery does not improve patient survival
• animal models show that lymph nodes may not filter tumour cells and this is supported by histological studies which show lymphatic bypass channels around nodes