FDR looked like he had terminal cancer at Yalta.
FDR was only 63 years old but his health had been undermined with many conditions— very high blood pressure, congestive heart failure and stress. He died of a stroke.
Several dermatologists and neurologists agree with you.
FDR had a pigmented mole (or lesion) above one eye for at least three decades.
News photographs show that it began to increase in size, and then suddenly disappeared.
The mole disappeared before Yalta, but I do not recall exactly how long before Yalta.
Was the mole surgically removed?
Or, did it vanish by itself, which often happens to a primary melanoma tumor.
Several dermatologists are on the record stating that they believe FDR was killed by metastatic melanoma.
The official cause of death was cerebral hemorrhage, but several neurologists have suggested that FDR had symptoms that were consistent with a metastatic brain cancer caused by melanoma.
Problem is - all of FDR's medical records - if any - have vanished.
A mystery for the ages, I suspect.