Thanks for your question. And here are the answers:

1. About the age and the results in general. It is a common practice to have the "last significant digit". For example, if I am 187 cm tall, it means 187 +- 1 cm or in other words 186 - 188. In case of practical use, this error is considered reasonable. If it's written 187.0 cm it usually means 187.0 +- 0.1 cm. In this case, the bones are dated to 1.6 - 1.800.000 years. How many years exactly - we don't know because those are the limits of our measurements.

2. If you go to the source article, you will find this sentence in the very first paragraph: The reported incidence of neoplastic disease in the extinct human lineage is rare. Only a few confirmed cases
   of Middle or Later Pleistocene dates (780 000 to 120 000 years old) have been reported. [References 1 and 2].

In other words, this is rare to find but not unique

1. Method for determination was, I quote: Nikon
   XTH225ST µXCT system, at an energy potential of 100 kV and resolution
   of 17 microns. Reconstruction was performed by E.J.O. and P.R.Q. using
   Avizo Amira 5.4 to generate both 2D orthoslice and 3D surface rendered
   views

In other words XCT, common device used in diagnostics.