Large red lump with black center on chicken belly-disgusting- what is it?

[LaFleche]

This is a breast button, a condition developing from an infected breast blister:

https://www.merckvetmanual.com/poultry/miscellaneous-conditions-of-poultry/breast-buttons-in-poultry

https://www.msdvetmanual.com/poultry/miscellaneous-conditions-of-poultry/breast-blisters-in-poultry

 

[Mrs J]

This is a breast button, a condition developing from an infected breast blister:

https://www.merckvetmanual.com/poultry/miscellaneous-conditions-of-poultry/breast-buttons-in-poultry

https://www.msdvetmanual.com/poultry/miscellaneous-conditions-of-poultry/breast-blisters-in-poultry

Brilliant article!! A great read and really educational