There are only 3 ways to descend below MSA.
1) Visually
2) Under Radar control
3) Following a full procedure.
Really? I don't suppose you have a reference?
What about a LSALT, if that is lower than the MSA?
What about in a published holding pattern, with a MHA lower than the MSA?
(In Australia) What if you are established on a VASIS associated with an ILS and within 10 miles?