I have used Sennheiser MD211 (omni) and AKG D200 (cardioid) dynamic mikes with my M10 without problems. I did not have to raise the recording volume so far that I got hum. There was room sound, depending on recording distance. Both mikes I used are low impedance professional mikes. I'm not familiar with your mike. Going Hi-Impedance mike into Low Impedance preamp causes loss of level, (and change in frequency response) if no matching transformer or circuit is used.
I use a Hosa XVM-105F, which is a short adapter cable, Female XLR to mini TRS. XLR Pin 2 is hot, and goes to tip and ring, Pins 1 and 3 are Ground, and go to Sleeve on the mini plug. This results in identical signals to each of L and R channels of the M10, which sums to mono. The M10 can not record true mono, IIRC. If for some reason your adapter cable does not provide signal to both channels of the Sony, and fails to ground one channel, you will get hum.
I also use a Hosa mini TRS stereo to dual XLR adapter cable to run from my external stereo preamp to the trs line input of the M10 for stereo field recording with phantom powered condensor mikes. It works fine, with no hum.
Dynamic mikes will have a worse S/N ratio than would phantom powered or self-battery powered condensor mikes, which put out more voltage by around 15 dB, but it shouldn't necessarily cause hum. I believe external mikes are unbalanced when run into the mike input of the Sony, which might increase susceptibility to environmental electrical noise, such as noise from dimmer switches, fluorescent ballast, halogen lectern lamp power supply, etc.
Have you checked the sensitivity setting on the M10? At least some mini disc recorders have a bit better S/N than the M10, but I don't think the difference should be enough to cause noticeable hum.
good luck with your problem. Simplest solution I can think of is a long XLR-XLR 3 wire cable run from lectern into an appopriate Hosa XLR to mini TRS cable/adapter, unless you have an impedance matching issue inherent in your mike.