Where as T1 has invaded the lining or the submucosa of the bladder it is usually listed under non invasive. I personally feel it should be listed under invasive or given its own classification so that the seriousness of it is not missed.
There is a very good diagram on this page showing the bladder and types of growth.
www.connecttoresearch.org/publications/86
Tumors invading the bladder muscle (invasive bladder cancer)
In this case, bladder cancer has grown into the thick muscle of the bladder wall, but has not spread to the lymph nodes or distant organs.
www.uroweb.org/fileadmin/user_upload/Guidelines/05%20TaT1%20Bladder%20Cancer.pdf
Approximately 75-85% of patients with bladder cancer present with disease confined to the mucosa (stage Ta-
CIS) or submucosa (stage T1).
www.mskcc.org/mskcc/html/348.cfm
Noninvasive Bladder Cancer
The majority of bladder cancers are transitional cell carcinomas (TCCs) that are noninvasive, or confined to the lining of the bladder.