Et Tumor, Brute?

Et Tumor, Brute? is a quest in Fallout: New Vegas which involves removing Caesar's Brain Tumor.

Quick Summary
Caesar needs you to get the supplies to cure his headaches and remove his brain tumor. You will need to find a functional Diagnostic Scanning Module or buy a set of surgical tools (999 caps, or more based on barter, at the New Vegas Medical Clinic. The tools can also be stolen from a cash register within the clinic.) and a Doctor's Bag to operate Caesar manually (medicine skill level 50 is needed). You have the option to cure him or rig the surgery to result in his death.(If the latter is chosen a speech check of 75 must be passed to keep the legion friendly)

If you have Arcade Gannon as a companion, you also have the option of selling him into slavery, as Caesar's personal doctor.

Detailed Summary
If you choose to find the Diagnostic Scanning Module, you must make your way towards the radiation and ghoul ridden Vault 34. You can find the vault north-northwest of the NCR's Camp Golf or EAST (not west) of the NCR's Sharecropper Farms near New Vegas. It is recommended that you bring several Rad Away and RadX. You will notice the radiation right off the bat as the entrance is brimming with radiation. Due to the intense radiation, there will be several geckos on the way in and once entering the vault you'll find approximately 20-30 ghouls of various types inside. Once inside your objective will be to get to the armory, however the door is locked and has nothing to do with this quest(there is notable loot down there however). Your objective is to get to a room called Security Section A which is under a flooded hallway. First you must search the vault for two terminal passwords. The security terminal password is in the first flooded area, on a dead Glowing One/vault technician under a desk, and the utility terminal password is through the clinic and into the next flooded area, on the right, on another vault technician. After finding the passwords, go to the door just before the entrance to the armory (this is the Utility Room), and activate the pump system on the terminal. Next go to the once-flooded area where you found the utility password, which will now be a closed door. Go through and make your way to the door that reads Security Station-A. In the security terminal you will find a broken down Auto-Doc with the replacement diagnostic scanning module. Now Return to Caesar, install the module in his Auto-Doc and perform the operation.

From the Security terminal you can continue on to the Notable Loot(see Notable Loot for know-how).

Another Summary
You can choose the harder method, to go to Vault 34 to find the parts for the auto-doc. They are located in Security Section A; loot the broken down auto-doc you find in the clinic.

Alternatively, you can simply buy the Surgical Tools for 1,189 caps (cost varies depending on your Barter skill - this is for a Barter skill of 70) at the New Vegas Medical Clinic. You don't even need to go to Vault 34, save doing that for the mission which involves it. You'll need a medical skill of 75 to work on Caesar. You can shortcut with a medical skill of 60 if you have the Wasteland Doctor Fatigues outfit (+5 Medical skill), and a copy of Today's Physician (+10 Medical skill), for a total medical skill of 75.