The cancerous rock nubs are organic growths that can be seen in the Metroid Prime Lair. Though they are quickly destroyed by the Metroid Prime's first energy wave attack, they yield several Ultra Energy Capsules for Samus to collect. They are grey stem-like structures with veins of blue Phazon, and have an orange orb at their top that appears to consist of Red Phazon. It would seem that they also mirror the Chozo Totems found above the room in the Artifact Temple. They are named in concept art of the game.
- Their name seems to refer to the fact that Phazon is a "cancerous element".
- In Dark Torvus Arena in Metroid Prime 2: Echoes, four statues circle the arena where the Boost Guardian is fought and are similar in appearance to the cancerous rock nub. The Boost Guardian can destroy the statues and they yield pickups for Samus' use.