Can a small potentially malignant growth be spreading cancer to other places in the body even if the tumor itself is not growing or changing?

Yes: If the potentially malignant growth is in actuality malignant then spread without any marked alteration in size is more than possible. Malignant growths do grow, but spreading is via a chemical MMP that allows the tumor cells to enter blood stream and forms small E-cadherins which enhance metastatic potential independent of size of the tumor.

It is possible,,,: Depending on the type of tumor and where it is in the body, a small tumor can metastasize or spread to other areas of the body. For example, a melanoma can stay the same in size, but if it penetrated the skin basement membrane, it can spread very quickly. Some breast cancers can also do this.