what is a cyst??

in my thyroid ultrasound report, it mentioned a 3.0mm cyst in the left thyroid lobe and it was not identified on the last year exam. my Dr told me to not worry and she said cyst is common.

but since i didn't have it last year, apparently something happened?

what is a cyst anyway? compares to nodule? should I not worry like my Dr. said?

thanks

[898]

It is blister filled with fluid [blood or colloid]; the cyst of this size can spontaneously resolve.

[helen1207]

here is my report, perhaps somebody can read it for me:

the thyroid gland is seen in it's normal location and is of normal size.
A 3.0 mm cyst is noted in the left thyroid lobe. this small cyst was not identified on the previous examination.

the isthmus is normal measuring 2.0mm

Impression:

small thyroid cyst, otherwise negative exam.
-------------------------------
my previous exam was last Sept and both sides were enlarged due to hashi.

appreciate your interpretation.