My chihuahua's perianal tumor shrunk after neutering. Should I worry?

Yes, it is true that dogs who haven't been neutered are prone to developing anal tumors. Given I can't see him in person, I can't say what the best course of action is for him, but following your vet's recommendation would be best for him in my opinion :-)

Hi there and thank you for using Petco Pet Education Center, formerly Petcoach! If the mass is small and not causing any problems, one option would be to leave it alone and keep an eye on it. The other option is to remove it now while it is small and manageable for surgery so that it is not something that is much larger that must be removed in a couple of years when Baxter will be older. I hope this helps!

A hepatitis adenoma is also known as a perianal adenoma. These are typically benign meaning they are not malignant and do not spread to other sites from the primary site. They typically occur on the prepuce, anal area or limbs. They can become necrotic and infected if not removed. The best course of treatment is surgical removal and castration as there is some belief that these are hormonally induced. Your biopsy report does not state whether the surgical margins were clean of abnormal cells. If they were clean, this tumor is not likely to recur in the same site. Your dog can possibly grow other ones but neutering him will help to reduce that likelihood.

Thanks for using Petco Pet Education Center, formerly Petcoach! This could be a benign or malignant growth. There is no way of knowing what it is just based on its appearance. This is often differentiated by a test called a fine needle aspirate (FNA) which is a pain free, inexpensive and easy procedure which in most cases will help reach a diagnosis. Sometimes a biopsy is needed for a definitive diagnosis. I recommend that you have him evaluated by your veterinarian for further assessment and treatment. I am really hoping for something benign. Good luck and have a good day!

This is probably just some scar tissue or a lipoma (a benign fatty tumor) but since it has recently popped up and seems to be growing I would recommend taking Tucker to the vet to have it checked. Your vet can do a fine needle aspirate and cytology. This is where, using a small needle, a sample of the cells are collected and then can be looked at under a microscope. This way your vet can determine what type of mass it is and if it needs to be removed. I hope this helps. Thanks for using Petco Pet Education Center, formerly Petcoach. Best of luck.

Many of these anal tumors are fed by sexual hormones such as testosterone. They are dependent on the hormones the body produces naturally (testosterone is naturally produced in the testicles) which makes such tumors grow. If you remove the hormone producing testicles (neutering) the hormone-dependent tumor gets starved and its growth will at least slow down. So castration is definitely advised. Anesthesia nowadays is quite safe and castration is not such a severe surgery. It may give your dog a longer life at a good quality of life.

Your veterinarian is most likely correct. From your photo this looks like a benign growth but it could be slightly infected which is why it looks different. It is not uncommon for these masses to get slightly raw/abrasions and have a small infection. I would consider having it removed at the time of his neuter so it will no longer pose any further issues.