From the history and information you have mentioned -Considering the long history, it probably should be a lipoma which is a benign swelling and not cancerous one .
Next Steps
Considering if it is a lipoma -You may need to treat it only , if you are having some difficulty with your normal action or cosmetically
Health Tips
This can usually occur in multiple area under the skin , mostly in your upper back. Though it usually don’t require treatment , you can consider surgical treatment if it is causing any discomfort.
Please note that there are some genetical syndromes which are associated with widespread lipoma which need to be considered. From the history you have given it doesn’t look like any . Please follow up with more history if the size increase or numbers increase