An indication of whether the excision margin was clear of the tumour and if so, by how much.

National Codes:

01	Excision margins are clear (distance from margin not stated)
02	Excision margins are clear (tumour >5mm from the margin)
03	Excision margins are clear (tumour >1mm but less than or equal to 5mm from the margin
04	Tumour is less than or equal to 1mm of excision margin, but does not reach margin
05	Tumour reaches tumour margin
06	Uncertain

References:
National Cancer Data Set 

This attribute is also known by these names:

Context	Alias
plural	EXCISION MARGINS