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I am sorry that you have been waiting for a response. I recently just logged onto the site and noted that your question hasn't yet been answered. I am a licensed veterinarian with over 25 years’ experience and would be happy work with you if you are still needing assistance.
I am sorry to have to tell you but there is no other treatment to remove or even decrease the size of an oozing tumor on his back. Regardless of if it is benign or more serious, many tumors, when they reach a large enough size will rupture and once that occurs, they will often become a big mess due to infection and bleeding. About all you can do is as you have been by keeping the hair trimmed short to avoid matting and moist dermatitis and to continue with an antiseptic cleanser to flush and clean the mass. Short of surgery, there really are no other options.
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