If it's on dry ice, make sure it's less than 5.5lbs and that you tell AA.
Example
Dry ice for packing perishable items
Allowed for travel?
Yes
Notes
You can travel with up to 5.5 lbs/2.5 kgs as carry-on if:
- Packed in a vented, hard plastic or heavy gauge styrofoam container
- You tell a ticket or gate agent
https://www.aa.com/i18n/travel-info/...cted-items.jsp