Hypochindriac worried about cyst in neck. Help?

First of all, thank you for taking the time to read this.
I am, indeed, an 18 year old, male/hispanic, hypochondriac. I am 5'9 and 125lbs.

Last year, I found a marble size, hard ball on the left side of my neck. It was deep in there, I actually
had trouble finding it every once in a while. It does not create a bulge whatsoever.

When I told my doctor about it, she said it was probably a swollen lymph node due to a cold or infection. I also
had a complete blood test and it came back normal.

Well, that was last year. This week, I looked for it again, and it is still there. I'm so worried because
I am fearing the worst: lymphoma, thyroid cancer or some sort of throat tumor. This entire year, it hasn't bothered me. It has not grown, or caused pain. I also have not had any physical symptoms. I actually feel really healthy and energetic.

Since I was a child, I've had fairly enlarged tonsils, even under my chin. Doctors always said I could have them removed but that it wasn't necessary.

My questions:

-If I've had this "ball mass" for 1.5+ years, maybe more, and it hasn't brought any concern, should I worry?
-can enlarged lymph nodes from previous infections (enlarged tonsils/tonsilitis) stay large for a number of years?
- Are cysts in the neck common in teens?
-In general, does it sound like it could potentially be cancer? Although I've been feeling extremely healthy this past year?

Thank You so much!

[Dr. Kokil Mathur]

Hi!
Actually a subcutaneous skin (under the skin) nodule—the size of a pea and firm, is usually due to a neurofibroma (connective and nerve tissue), a ganglion cyst or a lymph node. All are harmless benign conditions and rarely cause cancer. A mass which is not increasing in size should be left alone and not palpated around too much. It is probably any of the above and even a small lymph node can persist for years.
Please do not touch the lump daily. Once every 2-3 months take  a look and if the lump increases in size or becomes painful then consult a doctor immediately. Hope this helps. Take care!

The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.