Stage 0 
TNM T1, N0, M0 
Carcinoma in situ—a very early, microscopic, non-invasive cancer that has not spread below the membrane of the first layer of anal tissue .

Standard Treatment  Surgical removal of the tumor .

Five-Year Survival  100 percent 

Stage I 
TNM T1, N0, M0 
A tumor less than 2 cm (1 in.) with no evidence of spread to lymph nodes or other organs.

Standard Treatment  Small tumors of the skin around the anus and superficial well-differentiated cancers of the anal canal may be adequately treated by local excision with preservation of the sphincter muscle, with or without radiation therapy .