The most common causes of skin growths and lumps are tumors either benign or malignant, infection, or hematoma. I would suggest that since she seems to be in pain that you have her seen by your veterinarian as they will want to possibly biopsy the lump to determine the exact cause. Most tumors are not painful so that is actually a good sign that it seems sensitive but since it can be related to infection or injury and she is holding her tail differently I would recommend that you have her seen as soon as possible.
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*Cheryl K* Please click the
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