I realize this is an older thread but I wanted to share my experience. I'm searching the internet right now because a friend of mine has a rapidly growing malignant mass under his tongue/jaw. The doctors are all baffled. Anyway, I came across this thread. When I was younger my salivary gland became enflamed and hard like what is pictured. Then my gland became swollen under my jaw to the size of a golf ball and the resulting nerve pain was horrible. I went to a an ear nose throat doctor and found out I had something rare going on. Stones in my salivary gland! Long story short, The doctor ended up cutting the gland open (just a tiny slit under my tongue) and got a stone out the size of a matchhead. I will likely have this issue in the future. She said they aren't sure what causes them. Hope this helps some of you.