X-Men: The Brood Saga, Part 1
Chris Claremont (Writer), Dave Cockrum (Artist)
Beware the Brood! A vicious alien race intent on conquering the universe! Able to transform other species into their own kind, the Brood have infected each of the X-Men, and their metamorphoses will soon be complete. Now Wolverine, the only team member aware that the horrible transformation is about to occur, must enter a battle to save not only the lives of his teammates, but the universe itself!
Uncanny X-Men #162-164
This is reprinted in black and white, and is in a smaller size than regular trade paperbacks.