How Big is that Coccyx Mass, Cyst, Tumor, or Cancer?

  • Sometimes I find that my patients with tailbone pain (coccyx pain, coccydynia) actually have a mass, cyst, tumor, or cancer either within the tailbone itself or in the nearby tissues.
  • Examples can include pilonidal cyst, retro-rectal hamartoma (tailgut cyst), chordoma (a type of bone cancer that tends to happen at the coccyx and is often deadly), and abscess (a collection of pus or infected tissue).
  • Within an MRI report, or CT scan report, the radiologist who reads the images will typically report the size of any such abnormal structure in centimeters (cm).
  • Patients often see the centimeters listed and they will ask me, “Well, how big is that?”
  • (Since the United States has not adopted the metric system, many people here are not familiar with thinking about things in centimeter size.)
  • I recently came across a medical blog post (link below*) that gives examples of common foods, based on size (as measured by centimeters in diameter).
  • This is a great way to visualize how big your mass is, compared to foods that you are already familiar with.
How Big is that Coccyx Mass, Cyst, Tumor, or Cancer?
  • Pea = 1 cm
  • Grape = 2 cm
  • Walnut = 3.5 cm
  • Plum = 5 cm
  • Tennis ball = 6.5 cm
  • Orange = 6.6 cm
  • Baseball = 7.5 cm
  • Grapefruit = 10 cm
  • Cantaloupe = 12 cm
  • Honeydew melon = 16 cm


That excellent blog post was mostly about the size of uterine fibroids, but the same reference measurements would  of course apply for coccyx-related masses.

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