How would you approach a mucinous adenocarcinoma of the anal verge without anal canal involvement, status post excision with positive margins but without the possibility of additional surgery?  

The nodal drainage is dependent primarily on the anatomy and not the histology (the histology can determine the likelihood of nodal spread).  If the tumor is truly not involving the anal canal one has to assume that this is a cancer originating in the skin and I would manage it as a skin cancer...