What is this growth? It’s been there a while — it used to look like a boil, now the top seems to have lost blood flow but hasn’t fallen off, and the base has broken open. Does it need to be removed?

From the photo you uploaded, the dog likely has a polyp on its neck. If the polyp shows no other abnormality, it can generally be left alone, but if the polyp bleeds or ulcerates, infection can easily occur, and in that case it is recommended to take the dog to a veterinary hospital for removal promptly. After the polyp is cut out, the owner should follow the veterinarian’s instructions for post-operative care to prevent wound infection. If necessary, a biopsy should also be performed to check whether the dog’s cells are normal and ensure its health.