A soft bump under a cat’s armpit may have the following causes: Skin infection: This condition may be caused by a bacterial or fungal infection. Bacterial infections often cause purulent discharge on the skin, while fungal infections may cause itchy skin and cause your cat to scratch frequently. Cats with low immunity, infection from outside grass or cats and dogs with fungal infections, or wounds that are not cleaned may lead to fungal infections.

Subcutaneous lipoma: This is a common possibility. This bag may slide when palpated. If the cat shows no other symptoms and the lipoma has no tendency to grow larger, it can be observed first. However, if the lipoma shows signs of getting bigger or the cat has a pain reaction, it is recommended to take the cat to the hospital in time for an armpit B-ultrasound examination to determine whether there are abnormal blood flow signals, determine the location, and perform surgical removal.

Tumor: Although less common, the possibility of tumors cannot be ruled out. If there is pain when pressing the bag under the cat's armpit, it is recommended that the owner take the cat to the pet hospital for a B-ultrasound examination in time. After determining the location of the tumor, it can be removed surgically. After removal, pathological biopsy of the tumor is required to determine the nature of the tumor and determine subsequent treatment methods.