It's a Royal Queen I believe. I have a bunch of other palms very close to it, including a cluster of Chinese fan palms.

There's a lot of species of Ganoderma but that looks typical form. Some can be deadly on palms, and some don't affect them at all. That said, what you see is only the fruiting body, the bulk of the fungus will be inside. Unfortunately, being up on the trunk isn't a good sign. I have one species that starts out like that one and becomes dinner-plate sized, with the main part in the ground. Doesn't seem to harm anything. Best to check it out with your nursery, or with the agricultural department in your area.

Ganoderma, subgenus Elfvingia, don't know the species.

I read through a bunch of references as well as some videos by Dr. Steve Brown of UF/IFAS extension. It looks like that's what I have.

This 50' tall palm is less than 10' from my house, so if it falls during a storm it will be a huge issue. I think I have no choice but to cut it down due to the potential risk to the property. My understanding is that there is no cure foe this and the inside of the trunk will look much worse?

I wonder how much time I have. Whether I should do it ASAP, or wait another season to see if this mushroom grows into a larger cliff like conk. But that is just delaying the inevitable I am afraid.

It's a Royal (Roystonea), you'd be better off to fell it sooner than later. It won't be cheaper leaving it to later, but far more expensive if it comes down itself during a storm. I have felled large Roystonea myself, but there was plenty of room for a good drop. The trunk is very solid/heavy so can do a lot of damage coming down.

The palm is now gone. It did have the Ganoderma butt rot. The tree removal service that cut the top of the palm it was very fiberous, white and hard, but as they progressed to the bottom the saw went through it much easier, the trunk there was very soft and brown.

I will probably grind the stump but I need to find out if doing so would spread the fungus spores everywhere since I have many other palms near by.

Well, I think I have a serious problem. After I cut down the 50 foot tall royal palm, and carefully picked up the debris from the removal and paying attention to surrounding plants. I noticed three more findings that are really concerning.

{1} About ten feet from the royal palm, I have some concrete step stones. I found what looks like Ganoderma fungus growing on the side of one of these step stones! They are not growing on palms, but on the ground and on the step stone.

(2) I have a series of six pairs of Chinese fan palms, planted six feet, twelve feet, eighteen feet etc...from the royal palm. One of them, about 12 feet from the royal palm, has another fungus coming out of the ground near the base. I assume this is also ganoderma, but coming up from the root of the palm?

(3) Finally, there is a palm (coconut palm I think) stump about fifteen feet away, the stump has started to rot, no idea how long ago the palm was cut down. I have fungus coming out of the rotted stump.

I think this is an indication the entire area is infected with this fungus? Anything I can do except to hopelessly to allow it to do it's damage?

What an awefull thing to happen. I would be having a certified arborist come over.