4slenderthread is absolutely right, you need to get your dog to a vet as soon as you possibly can. Any lump that changes size, shape or starts to bleed should be considered suspicious. Hopefully it will be nothing serious, but even if it is, catch it early enough and there's a good chance that treatment and/or surgery can prevent a cancerous growth spreading into the lymphatic system (which is how these things spread to vital organs and cause terminal problems).
Please let us know what your vet says - and fingers crossed it's nothing to worry about. Tony
Hello there Krissy -
I have never answered a dog question on med help before - but this forum is relatively new ... so here goes. Despite your dogs young age, she is a bullmastiff and some breeders have had a number of problems - two of the most common are - tumors, and hip dysplasia.I had a chinese pug that began with a 'cyst' looking growth on her back, which sometimes bled. It then began to grow quickly, before I realized it the growth was huge beneathe the 'cyst.' She had a biopsy done and then immediate surgery, due to the fact it was actually a malignant tumor. Oddly enough, she recovered extremely well and lived happily for many more years! I only tell you that story so you know how important it is to get to the Vet as soon as possible. It MAY only be a cyst ... I certainly hope so, but you don''t want to wait and find out differently. If I had waited any longer, thinking it was nothing serious, I could have loss my beloved Chloe years before I needed too! Go ahead and make your Vet appt. today - you'll feel better when this is all over. I hope you will send me a message and let me know how everything turned out! Take Care ...