They knew what type it was, most likely squamous cell carcinoma as the most common one that occurs in that location. They probably sent the removed tissue to pathology which is where they saw malignant cells in or very near the margin. Those are very easy to identify under the microscope because of the very large nucleus. They could have, but likely did not explore this further. They still have that sample because they are required to keep it x number of years to refer back to.

The list of what they could have explored is very long, some of it very expensive. Were it other tissue from something more dangerous and aggressive in their minds, that could have included genetic testing that would have revealed the innermost secrets of it. This location is not known for it, but they could’ve looked for it being p-16 positive, which be a common question checking for HPV etiology if it had been on the base of your tongue in the lymph tissues there. And if you ultimately needed any kind of immunotherapy, that sample would give them the genetic markers to determine you were a candidate and for which one. So they will be keeping that sample long after u are out of the woods.