Welcome to Justanswer! I am Dr. Altman and happy to assist you both today!
I am sorry to hear Bailey has this lump. It sounds like it might be an abscess or an infection from what you describe even though it is not itchy nor bothering her at this point. I don't like that it is well attached and how large it is though
First and foremost, in order to determine if they are benign (noncancerous and/ or infectious) lumps versus malignant (cancerous) lumps is to have your veterinarian evaluate and aspirate (poke with a needle) the lumps to evaluate the material under the microscope
This is really the only way to differentiate the concerning from the non concerning lumps definitively because a cancerous versus a noncancerous lump can appear identical on presentation
Evaluation under the microscope will be looking at the lump at a cellular level. Do the cells look normal, is it sebaceous or oil material that is benign or even fatty material indicating a lipoma or are the cells abnormal in appearance? This information is critical in order to diagnose the lump origin and whether it should be removed sooner versus later
Some tell tale signs that a lump might be more of a concern include whether it is rapidly growing, it is bothersome (scratching, licking), it is not easily picked up from the underlying tissue indicating it is attached to the muscle layer. This can be helpful but not 100 % definitive as a fine needle aspiration would be
I always advise photographing the lump with a ruler or coin next to the lump to measure the size weekly or in dark skinned dogs where it is not as readily viewable measuring with a ruler on a regular basis
With the size, the fact it is draining, and she often likes to be in the bushes my first instinct is this is infectious or inflammatory in nature but unfortunately the only way to know for sure is having your veterinarian evaluate and aspirate the area.
Until then, please use warm water soaks to remove the dried blood and hopefully aid in consolidating the mass more readily in continued drainage and reduce risk of rupture and limit her scratching at it if she does become more irritated and wants to rub it.
Please let me know if this information makes sense and any additional questions I can assist with today
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