Unknown Bump on 8month old

[kramttocs]

Hi,
Our son got this bump around 4 months and it has been present in some form since then. It doesn't bother him but it concerns us (we have an appointment but couldn't get in for a few weeks). Sometimes it looks pretty bad, like in the pictures, other times it's just a red bump without the yellow 'bubbles'. The pediatrician thinks it's a birthmark.
Any ideas?
Thanks!

[Dr.Saiyan]

Hi Scott!welcome to DermaTalk. The lesions seems like solitary mastocytoma, which occurs within 6 months after birth. The biopsy and histopathological report is confirmatory. As you are visiting the dermatologist, I hope he will help us confirm the diagnosis and treat accordingly.Hope you will let us know the result, we will be happy to hear from you.

[kramttocs]

Went to the dermatologist this past week, and he also diagnosed it as solitary mastocytoma.
Thanks!