I've seen this story that Caesar was autopsied, or even that he was the first autopsy, for years now, and I have no idea why. There's no evidence that Caesar was autopsied, and there'scertainly no indication why there would have been one. The autopsy thing comes from a brief comment at Suet., Iul., 82.3:

Nec in tot vulneribus, ut Antistius medicus existimabat, letale ullum repertum est, nisi quod secundo loco in pectore acceperat.

And among so many wounds not one was found to be lethal, in the opinion of Antistius the [probably his] doctor, except the second one he received in the chest

That's it. Nobody else mentions Antistius either. There's no reason to suspect any kind of thorough examination. For all we know they carried Caesar's body to his house and his doctor, which is what Antistius pretty much has to be, said "He's dead, Jim. Can't you idiots see he got yoinked in the heart?" I don't understand why Internet mythmakingpop history has turned this into an autopsy but not, say, Xenophon's report at An., 2.6.29 on the deaths of Clearchus and Meno, just to use an obviously not parallel example. This whole "first" autopsy thing is doubly silly. What, because the dude is named? So we're supposed to think that nobody bothered to look at Hipparchus' body, which is all we know Antistius did, because nobody names a doctor?