toner in imaging drum cartridge

[shel1952]

Before I replace the imaging drum unit on my HP MFP179fnw laser printer, I need to ask if it is normal for toner powder to accumulate inside the drum cartridge?  I want to rule out that the cause for the ghosting on lower third of page is anything other than drum failure.  If something is depositing toner inside the drum unit, that could be getting picked up on the rotations to soil the drum, then the same will happen wth a new drum, presumably.    The machine has printed fewer than 200 copies so the problem and the cost of replacement are off-putting.  Don't want to install a new drum and find the same problem occurring. I have cleaned the drum but the ghosting remains. 

[Valsimot]

The drum also collects some waste toner, but if the printer printer under 200 pages the drum should be clean or minimum signs of toner dust.