A tumor cannot be considered as an organ, its activities not being coordinated with those of the body.

A part of the body it certainly is, but in the household economy it is to be considered as a wild and lawless guest, not influenced by or conforming with the regulations of the household.
The rapidity of growth varies; certain tumors for years increase but little in size, while others may be seen to increase from day to day.
The growth is often intermittent, periods of great activity of growth alternating with periods of quiescence.

The nutrition and growth of a tumor is only slightly influenced by the condition of nutrition of the bearer.

Its cells have a greater avidity for food than have those of the body, and, like the growing bones of an insufficiently fed animal, growth in some cases seems to take place at the expense of the body, the normal cells not obtaining sufficient nutriment to repair their waste.
A tumor may be of any size: so small as to be invisible to the naked eye, or its weight may exceed that of the individual who bears it.

The limitations to its growth are extrinsic and not intrinsic.