Sean Long scored 20 points as St Helens moved three points clear at the top of the Super League table, inflicting a club record defeat on relegated Leigh.
Leigh (0) 4
St Helens (32) 78
Tries: Bennett, Long 2, Wellens, Albert, Higham,
Roby, P. Anderson 2, Gardner 2, Cunningham, Graham, Fa'asavalu
Goals: Long 7, Lyon, Hooper 3
Long and Mike Bennett both went over in the first five minutes, with Paul Wellens and the returning Micky Higham helping Saints to a 32-0 interval lead.
James Roby's 70-metre interception try after half-time added to Leigh's agony.
Ben Cooper broke Leigh's duck late on but Paul Anderson found time to notch another try for the rampant Saints.
Leigh caretaker coach Heath Cruickshank was left looking for positives after another crushing defeat.
"We've been doing well in training and it was pretty disappointing to come up with a performance like that," he said.
"Believe it or not, we had an awesome week in training despite everything that's happened this week.
"One positive is the kids who have stepped up recently have done well. That's something we can build on."
Saints coach Daniel Anderson was already looking forward to their next game, against Wigan next Friday.
"If we win on Friday we are Minor Premiers, which gives us a home semi-final, but Wigan are fighting for a top-six position," he said.
"We have to build momentum and are going all right at the moment. I thought we did the little things well.
"It must be very hard for Leigh to keep their focus in their situation."
Leigh: Wilshere, Owen, Jackson, Cooper, Maden, Forber, J. Duffy, Fleary, Mears, Marshall, Leafa, Stapleton, Coleman. Replacements: Sturm, Stevens, Maddocks, C. Hill.
St Helens: Wellens, Albert, Lyon, Talau, Gardner, Hooper, Long, Fozzard, Cunningham, P. Anderson, Gilmour, Bennett, Roby. Replacements: Hardman, Higham, Graham, Fa'asavalu.
Referee: Karl Kirkpatrick (Warrington).