creamentas

A United States Permanent Resident Card, known informally as a green card (due to the color of some earlier variants), is an identification card attesting to the permanent resident status of an alien in the United States of America. The Permanent Resident Card is also called Form I-551. According to the Section 264 of the Immigration and Nationality Act is that every alien in the United States shall be issued a certificate of alien registration which shall be prescribed under regulation. Moreover the specific requirements and procedures for applying to renew an expiring permanent resident card are set forth in the Code of Federal Regulations [CFR] at 8 CFR § 264.5.

A permanent resident card that was issued under the Form I -551 valid for ten years needs to be renewed if it has expired or will expire within six months.
Now if a situation arises that your permanent resident card expires when you are outside the United States you should contact the nearest American Consulate, USCIS office, or Port of Entry, before attempting to file Form I-90 for a renewal I-551 card.
Finally if your appeal for a green card renewal is denied you may submit a motion to reopen or a motion to reconsider with the same office that made the unfavorable decision.