What does the term "recurrence" primarily refer to in oncology?

The term "recurrence" in oncology primarily refers to the regrowth of cancer cells thought to be inactive after treatment. This situation occurs when cancer that was previously treated and went into remission returns either in the original location or in a different part of the body.

While the other options provide related terms and concepts, they are not accurately defined as recurrence. The appearance of a new cancer that is not related to a previous cancer refers to a second primary cancer, which is distinct from recurrence. Similarly, a type of cancer arising from different cells in the same primary site describes a new cancer entity (which may be a local recurrence but is specifically referring to a different histological diagnosis) rather than the recurrence of the original cancer itself.

In summary, recurrence specifically involves the return of the original cancer after treatment and not the development of new or unrelated cancers.