A robot designed to miniaturize itself (à la Fantastic Voyage) is sent into its designer to combat cancer.
This is actually not a bad story, even if I did neglect to review it until I got around to Robots from Asimov’s. Sucking in the miniaturization technology from somebody else’s idea (namely Fantastic Voyage) seems a bit of a cheat until you remember that the movie doesn’t explain how the miniaturization works or why one can only stay miniaturized so long, but the book does, so the “how” of the miniaturization is Asimov’s.
But that’s a side issue.
The ending here is weak, as the robot destroys itself rather than risk an unsafe deminiaturization that would kill its patient and creator, and the creator mourns the loss of the robot over his own cure of cancer. Had that element been handled better it would have been a reasonably solid story. The set-up is slow, and we spend perhaps a touch too long with the hand-wringing wife and not enough with the patient, which would have made the story more moving.
But it’s not a bad story. Certainly is above average among Asimov’s later short works.