Left posterior fossa arachnoid cyst & precocious puberty

We recently had my son seen by a ped endocronologist regarding early onset of puberty. He is not quite 10 1/2 and his voice is deepened, he is covered in hair(everywhere), and is on a rapid growth spurt. There is no denying he is in full blow puberty. However, the doc ordered an MRI to rule out any tumors causing the early onset.

We got the report from our local hospital, where the test was performed, to take with us to the next appointment just in case the report was not delivered to the doc. My husband works in radiology and I have just enough med training to aware.

The impression of the MRI reads: there is asymmetric prominence of the left posterior fossa. Finding likely represents a posterior fossa arachnoid cyst. other likely differential includes Danny-Walker variant(think they meant Dandy)Measures approx.1.6cm. Otherwise unremarkable.

So, this doesn't sound like great news but I'm not sure what to make of it. Could anyone please tell me if this is a common finding when looking for causes of precocious puberty and possible is related to his current issue? Or is this probably just an incidential finding that happens and aren't related and not big deal?

Just wanting to wrap my head around this and potentially what to expect? I have read some scary and not so scary stuff in my search and need others opinions.Thanks!