So.... lumps, bumps, etc... are more or less normal. Dogs get fatty tumors all over, including on the scrotum.
Age 4 with lump - I would be concerned and have it checked. But the vet may pinch and feel and decide it is low concern and tell you to just keep an eye on it. Changes in size, appearance, feel, etc... would be reasons to move forward and neuter the dog. Or you could call for peace of mind and just have the dog neutered. Depending on actual location of the lump, that would not necessarily get rid of it just quick neuter.
I will say that fatty tumors or other benign growths on a 4 year old is unusual. It's more of an old dog thing (age 8+).
Age 4 with lump - I would be concerned and have it checked. But the vet may pinch and feel and decide it is low concern and tell you to just keep an eye on it. Changes in size, appearance, feel, etc... would be reasons to move forward and neuter the dog. Or you could call for peace of mind and just have the dog neutered. Depending on actual location of the lump, that would not necessarily get rid of it just quick neuter.
I will say that fatty tumors or other benign growths on a 4 year old is unusual. It's more of an old dog thing (age 8+).