My permanent resident card (green card) expired a couple of years ago. Does this mean that I can be deported? I have lived in this country for 27 years and always paid taxes. However, there have been a couple of years where I did not file my taxes.

Why don't you apply for renewal? Are you a criminal?

Unconditional LPR status doesn't expire, only card does.

If your LPR status is unconditional then simply fill out the required form and ask for renewal of your card.

AF1 is correct. Just fill out the form and renew your card. You will need the card if you leave the country.

Unconditional LPR status doesn't expire, but it can be revoked. Бойся.

Naturalized USC can be revoked as well.

It's irrelevant to OP question.

It is, because OP did not tell the whole story.
She is in trouble and can not apply for renewal.

Nothing in the OP post suggests that "She is in trouble", but in the worst case scenario she will be deported, which is not a big deal anyway

Thanks, AF1. Appears pretty simple since my status is unconditional. I assume that I can still work as long as my employer does not audit their I-9 records. They have never requested an updated card.