My 4 yr old female boxer has a history of 3 pilomatricomas removed 02/07 and since has developed 6 new tumors presenting as the previously removed tumors. The lesions do not appear to cause her any pain or discomfort. The local vets do not have a know cause for her to keep developing new tumors. With the reputation the breed has for malignant skin tumors, I am very concerned a new tumor might be mistaken for benign and go untreated. Having said that, the dangers of sedation for every new tumor is not a solution. Please help me find an etiology.
Thank you
Sommer

This is a tough one. Boxers are definitely a tumor-forming breed. I found a link for you that seems to be thorough:
Cancer Information, Research, and Treatment for all Types of Cancer | OncoLink
This is apparently a very uncommon tumor to begin with, and it is even more rarely malignant. Two things worry me about your dog: the fact that there are multiple masses instead of one solitary lesion, and that the article above consistently lists Boxers as a breed with reduced risk. (I didn't know Boxers were at a reduced risk for any kind of tumor.)
You might consider having the new masses removed and sent to a different laboratory. Identifying tumor tissue types is a judgement call sometimes, and different pathologists may interpret the specimens differently. If they are confirmed benign pilomatricomas, then discuss the game plan with your vet. One alternative might be to have him do a fine-needle aspiration of any new mass. This does not require sedation. It is not as informative as a full biopsy, but it should help rule out mast cell tumor--one of the most common Boxer cancers.