Greetings.
The short answer is: no. It is too much of a long shot to have a benign mass on kidney as THE only syphilis symptom - with a negative RPR.
It is way more likely to be a probe implanted by an evil alien overlord.
Why do you think syphilis? It must be just a cyst. Many people have it.
Tertiary syphilis, on the contrary, is super rare.
Have you ever had positive RPR tests before? Have you ever had confirmed syphilis?