Mass General is indeed a CCC -- a comprehensive cancer center, meaning that it uses a team approach to dealing with an individual case, bringing the knowledge and experience from a variety of specialties to each treatment plan. (In other words, it takes a "comprehensive" approach to treatment.)

What MGH isn't is a National Cancer Institute-designated comprehensive cancer center. Institutions choose to apply to the NCI for that designation, which involves a peer-review process and a lot of paperwork. The NCI provides funding for research, and the terms "NCI-designated comprehensive cancer center" and "NCI-designated cancer center" are indications of research interests, not the quality or scope of patient care.

The NCI defines "comprehensive cancer center" differently from how the term is usually used on this message board (for that, see the first paragraph of this post). NCI designation of a facility as a "comprehensive cancer center" means that the institution is involved in three types of research: laboratory, clinical and population-based. All NCI-designated comprehensive cancer centers also treat patients. An NCI-designated "cancer center" concentrates research in one or two of those areas, and a few of these facilities -- like the Wistar Institute in Philadelphia, the Koch Institute at MIT in Cambridge, Mass., or the Salk Institute in San Diego -- do research only. Further information is available here: http://cancercenters.cancer.gov/documents/CCSG_Guidelines.pdf (see page 7 for the NCI's definitions).

According to the most recent USNews rankings, Mass General is #7 on the list of best hospitals for cancer treatment -- higher than most of the institutions that are NCI-designated CCCs or CCs. So you would certainly be in good hands there.