Fluid filled lump on son's head

My son is 14 and came to me today and told me that he had this "mushy lump" on his head.  I felt it and it was really gross feeling and about the diameter of a baseball.  I immediately took him to the doctor and saw a Nurse Practitioner.  She said that she didn't know what it was, but just watch it and see if it get's bigger and bring him back.  He does not recall a injury to the head.  When you feel this thing it is like a watery substance under the scalp and when you push on it it feels mushy.  You can not feel the skull bone when you push on it because of the amount of fluid.  She also said that it may be a cysts?  Aren't cysts more firm and not mushy and gushy?  I don't know what to do and I am scared that they are not looking into it yet.  Could you please help me?

[Dr. Kokil Mathur]

Hi
Welcome to the MedHelp forum!
A soft lump on head can be a hematoma, or localized collection of blood. Your son may not remember hitting his head, but it could have happened. The other possibility is that it is a cyst. A cyst is tense only when completely filled with fluid. The third possibility is that the lump is a lipoma that has not got well organized yet.
A CT scan of the lump will give a fair idea of what it is.
It is difficult to comment beyond this at this stage. Please let me know if there is any thing else and do keep me posted. Take care!