What could a semi-hard lump under my tongue be?

Stone vs. tumor : Under the tongue on each side, there is a major salivary gland called the sublingual gland. If a mass arises in this gland, it could be a stone, or a growth. The likelihood of a malignancy (cancer) in this particular gland is upwards of 50%. It could also be an oral cancer outside of the gland, especially in oral tobacco users and alcoholics. An urgent evaluation by otolaryngologist is in order.

Different Diagnoses: There are salivary glands in the floor of mouth & they can have infections, stones that block drainage of saliva, benign and cancer tumors. There are blood vessel abnormalities that can feel like a lump. There are also swollen lymph nodes both infectious and neoplastic. The most serious possibility is squamous cell carcinoma. You need to see a dentist who can evaluate the diagnosis and refer you.

See your dentist: You should see your dentist to rule out a more severe cause such as oral cancer. He will be able to recommend treatment if necessary.