The term tumour (plural: tumours) is versatile. It is synonymous with swelling, enlargement, but also with ulcers, plants, etc..
Even in a normal inflammation, a local swelling develops as an inflammation symptom. These tumours are called non-neoplastic tumours because they arise from an accumulation of already existing plasma.
Tumours that arise from the accumulation of new plasma, e.g. through cell proliferation, are referred to as neoplastic tumours.
https://de.wikipedia.org/wiki/Tumor (Wikipedia CC-by-sa-3.0)