Chicken Peeps (& those who enjoy gross)

[2DogsFarm]

This grossity has been on the back of my Buff Orp’s head for at least a couple months.
Started as a bare spot - like a rooster might leave - then grew to golf ball size. I tried opening it when it first grew - nothing apparent, no pus even with applied pressure & I did not want to cut deeper.
Lately it has formed these dark “scabs”.
Does not appear to bother her, she is eating, drinking as usual. Other hens aren’t picking at her.
Here is the location:

And a close up:

Any ideas on what it is?
My guess is tumor.
If she begins to fail, I will cull her, but now she seems fine, just disfigured

[GoodTimes]

Chickens don’t have liquid puss like we do. Their pus is more like a solidified yellow cheesy or scrambled egg texture. Lash eggs and bumblefoot for example are pus infections.

What was the texture like when you dug around? Usually chicken pus doesn’t really adhere to the surrounding tissue so once you soften everything up a little you can pull it out with tweezers.

[2DogsFarm]

Google told me this, but I hesitated to dig around much under the initial cut.
I cut deep enough so she bled.

It’s been so long now, I imagine an abcess-type of pus-producing infection would be much worse & have made her much sicker.
Am I wrong?

[MrsFitzDarcy_amp_Feliks]

I had the comb of a salmon Faverolles cockerel get something icky like that. The comb actually came off when I picked at it. Unfortunately, he didn’t make it. I sent the link to a chicken friend, who’s pretty good at home diagnosing.

My buddy said that Marek’s can cause skin tumors.

[GoodTimes]

Does it smell?

[2DogsFarm]

No smell.
If it is Marek’s the only sign is the external tumor.
She has no problem with balance or walking. Her weight is not overly affected, though IMO an Orpington s/b heftier. I’m pretty sure these were hatchery chicks, as the rooster in the group was presented as a hen & showed signs after about a month.
She was one of 4 (3 hens & 1 rooster) gifted to me when they were about at point-of-lay - maybe 4mos?

No other chicken seems affected.
I had 2 older (2 & 6years) hens & a (2yo) rooster when the new bunch arrived in October.

I suppose I should cull her, but that probably won’t prevent further infection to the rest of the flock.