Hisano has sliced A LOT of souffle pearls! There are two little pearls growing inside a souffle!
By virture of that the incidence of occurrence is low.
I've marked the image for comments.
The red line appears to be the incision along the sac where the pearl was expressed and the mud packed. Inside the green line, there's a gap between edges of the cut, bridged by conchiolin, then aragonite on successive layers. For whatever reason by prolapse, affinity or infection... pearls formed at that level. Most likely due to granular tissue nucleation aka scar.
At first glance, I thought these may have been present in the pearl sac only to end up in the muck, but two close together and fused along a scar line suggests they formed subsequent to the packing. Likewise, they are not "nacred" to the pearl like a mabe or a blister, insomuch as fused to the lining by their pearl sac.
They're technically natural although convention would have them as cultural. There was human intervention, but clearly coincidental and unintentional.
An intriguing specimen.