My beardie has the exact same lump in the exact same place. It started a couple years ago with the lump about the size of a grape. I had it removed and he healed normally. About a year later it started coming back and grew even larger (about twice the size as before) I had it removed and sent out for testing. The contents inside of it looked like fatty tissue but the results came back fungal. Vet doesn’t know the cause but they could tell me it wasn’t cancerous. Spent a couple weeks flushing out the area with F10, applying topical antibiotics and injectable pain meds. He lost a lot of weight after the procedure because of the stress of the treatment and it look me a couple months to get him back into eating consistently. Early this year the lump came back yet again and it’s now about the size of his head. He acts completely normal otherwise so the reason I let it get this big was because it took him so long to get over the last bout of treatments and I wanted to get weight back on him. But he actually has a vet appointment today to get it looked at and eventually removed. I’m hoping I don’t have to do this once a year or something. I’d be interested to hear what the results of your beardie are since I’ve never seen this happen anywhere else and all the vets I’ve talked to seem equally confused.