My son, who is three years old, grabbed a flashlight and wanted to look at my tonsils today. So, to have fun, I looked at his and noticed something very peculiar that has me a little shaken. It may be normal, but I'm not sure. When he stuck out his tongue and said "ahhh," I noticed that below his tonsils in the center was a "nodule" that stuck up. It disappeared when he didn't say anything. It is a square-like shape about one quarter of an inch long. Is this normal?

L.M.

Okay ... let me reassure you before I worry you. I hope the net result will not be total confusion!

First the reassurance. You probably saw your son's epiglottis. The epiglottis is a fairly large piece of cartilage that is covered with mucosa, the same pink tissue that lines the mouth and throat. While it is typically described as leaf-shaped, a more squared-off shape is also very common. The epiglottis acts as a flap valve, protecting the airway when people swallow.

In infants and toddlers, the larynx is much higher in the throat than it is in teenagers and adults. It is not at all uncommon to see the epiglottis when you ask a toddler to say, "ahhh." Occasionally, this odd bit of anatomy persists into adult life.

Now for the worrisome stuff. There are a variety of lumps that can grow at the base of the tongue in toddlers. One possibility, for example, is known as a lingual thyroid. The thyroid gland begins developing when the embryo is a mere 4-5mm long. The gland starts out as a lump of tissue at the base of what will eventually become the tongue. It then descends in the neck, eventually assuming its usual location. In cases of lingual thyroid, we assume that this descent simply did not occur, since the thyroid gland instead develops as a lump at the base of the tongue.

If this isn't worrisome enough, there are a number of true tumors, both benign and malignant, that can develop at the base of the tongue. Fortunately, all of these tumors (along with lingual thyroids) are fairly uncommon.

Without actually seeing your son, I cannot reassure you 100 percent that what you are looking at is normal anatomy and not a dreadful tumor. The odds are greatly in his favor, but I still think you would probably sleep a little easier if you brought him to his pediatrician for a quick peek.