Please help me look at what is wrong with my cat’s tail.

A lump at the base of the tail needs veterinary diagnosis to determine its nature. A red, swollen hard bump can have several causes. First, traumatic infection causes local redness, heat, pain and possibly abscess needing cleaning, drainage and topical antibiotics.

Second, a subcutaneous tumor appears as a hard lump under the skin and needs a cytology test to tell if it is benign or malignant; tumors usually need surgical removal and malignant ones need follow-up. Third, skin disease can also cause a red swollen bump that later softens, so treat skin issues promptly.