Karl developed the X-rays for Juliet after Ben complained of back pain. Upon examining them, Juliet told Ben he had a tumor on his L-4 vertebrae. The news surprised Ben, who previously told Juliet that no one on the Island ever had cancer. ("One of Us")
Jack later asked Juliet to whom the X-rays belonged to, saying:
"Those are spinal X-rays, and they belong to a man about 40 years old. And whoever he is, he has a very large tumor on his L4 vertebra. And I just happen to be a spinal surgeon. So you tell me, Juliet, who am I here to save?"
In "The Cost of Living", it was revealed that the X-ray belonged to Ben, and that he wanted Jack to operate on him. Juliet tried to convince Jack to intentionally botch the surgery, killing Ben but thereby making it appear to be either an accident or an otherwise fatal outcome.
- L4 stands for lumbar series (lower back) #4 (or #23rd/33 backbones). In this case, the tumor in question is seen as the second from the top of the film (the one with uneven opacity).
- In a standard spinal series, the location of this tumor would more accurately be assessed as L2, due to proximity to the rib cage.
- The "R" in the corner labels the right side of the individual, to orient the X-ray reader. In this case, the patient would be facing the viewer.
- There is no name and information on the X-ray, as is the hospital standard.
- Medical staff can typically differentiate male from female chest and spinal X-rays by the breast shadow (though this is lower down and would be difficult due to cutoff). However age is not actually possible to pinpoint as Jack did in the storyline.
- Although Jack correctly recognized the malignancy as a lumbar tumor (either L2 or L4), later he incorrectly stated that Ben's symptoms would be in his fingers and toes. Such symptoms are generally characteristic of cervical tumors - in the neck, not lower back (which would be toes only).
- The X-rays were taken at the latest on September 20, because Ben said, "Two days after I found out I had a tumor on my spine, a spinal surgeon fell out of the sky," whereas Oceanic flight 815 crashed on September 22, 2004.
- This assumes both that Ben was telling the truth, and that time on the island and off the island flowed at the same rate. Ben often lied, and it has been strongly suggested by the events and the producers that time on the island flowed differently than time outside it.
- The X-rays were developed by Karl and delivered to Juliet's house in the flashback for "One of Us". She stored them in a manila envelope, later confronting Ben with them, and tried to reveal them to Amelia just before the book club meeting on the day of the crash, as seen in "The Envelope".
According to the audio commentary for "A Tale of Two Cities" on the Season 3 DVD set, Elizabeth Mitchell shot a scene in which she is looking at the X-rays in her house. This bit was supposed to be in the 'walking through Juliet's house' sequence at the episode's start, before the book club meeting, but it was cut in post-production. This would have introduced the X-ray three episodes earlier, but the audience would have had no information about it yet. It appears that this scene has been used for mobisode "The Envelope".