Hello, I'm Dr. Kara and I have over 20 years of experience as a veterinarian.
I'd like to help with your concerns about Sirocco's round cell tumor on his ear.
The most common types of round cell tumors found in this location in order of likelihood are mast cell tumors, histiocytomas, plasma cell tumors and cutaneous lymphoma.
Mast cell tumors do pop and grow quickly, especially if they are bumped, and they have variable degrees of malignancy, some can be treated with just surgical removal, some are quite aggressive and will spread deep into tissue and to local lymph nodes. The only way to know for sure how malignant the tumor is to remove the tumor with very wide margins and have it biopsied, taking care to have the pathologist look at margins to make sure that they are clear. I also recommend aspirating his local lymph node that drains the ear or biopsying it to look for metastatic spread. That will determine what sort of treatment he would need post-operatively. If there are tumor cells in his lymph node chemotherapy would be advised. Mast cell tumors on the face and ears tend to be more aggressive types. Because of that it may be best to remove a good portion of the ear pinnae (flap) to make sure that we do get clear margins. Though this is often disheartening to owners because it may not be as cosmetic, it will give your his best chance at beating his cancer the first time around. If we do not have clear margins then radiation and chemotherapy are recommended.
Histiocytomas are growths that pop up suddenly, grow quickly for a month or so and then tend to regress and resolve on their own within 2 to 3 months. They are most common in young dogs on the face, ears and legs and paws. But older dogs can get them too and if they scratch them they may not resolve because they become inflamed or can get infected when rubbed or scratched. If they don't resolve on their own they should be removed.
Plasma Cell tumor is possible but these are seen less commonly then mast cell tumors or histiocytomas. They can behave aggressively but are usually only a local problem and if good margins are achieved, no further treatment is needed after surgery and recurrence is less likely
Cutaneous lymphoma is less likely because it doesn't present as a primary tumor, rather it tends to show up as clusters of tumors. Treatment is chemotherapy as removing the tumors is not helpful, more will simply occur.
I agree that this should be dealt with as soon as possible but make sure wide margins are achieved and the local lymph nodes are assessed.
Best of luck with your fellow, please let me know if you have any further questions.