Psammoma body in papillary thyroid carcinomaMaybe I missed that pathology lecture, or maybe I was sleeping when the terms were discussed.Β For whatever reason, I have always had a hard time with dystrophic and metastatic calcification.Β I could remember that one type of calcification was simply the result of having a high calcium level, but I couldn’t really define the terms and keep straight which one was which. If you have had that problem, maybe this will help clear it up once and for all.

Dystrophic calcification
This type of calcification is seen in areas of necrosis. Some examples of lesions with dystrophic calcification include: atherosclerotic plaques, aging or damaged heart valves, and tuberculous lymph nodes.

The process is thought to start in membrane-bound vesicles within cells. When the membrane of a vesicle gets damaged, calcium binds to the phospholipid in the membrane. Phosphatases within the membrane add phosphate groups to the calcium, forming calcium phosphate (this is similar to the hydroxyapatite you see in regular bone). If you get enough calcium phosphate, it clumps together as a visible deposit, which rearranges itself (cool!) to generate a microcrystal (which propagates and leads to more calcium deposition).

Macroscopically, dystrophic calcification looks like tiny, white, gritty granules. Microscopically, you see basophilic granules (or sometimes amorphous deposits) either inside or outside of cells. Sometimes there is so much calcium that heterotopic bone is formed (whoa). Sometimes, single necrotic cells act like little grains of sand around which a “pearl” of calcium is deposited. This is called a psammoma body (which is appropriate since psammos is Greek for sand). Check out the very pretty psammoma body above. Psammoma bodies are particularly common in papillary carcinomas (like papillary thyroid carcinoma).Β 

So what does it mean if you see dystrophic calcification? Well, it can just mean that the tissue has been previously injured. However, it can also indicate that there is ongoing organ dysfunction (for example, you see dystrophic calcification in calcific valvular disease). It can also be helpful if you’re trying to diagnose a carcinoma (if you have a thyroid carcinoma and you don’t know whether it’s follicular or papillary, seeing psammoma bodies is a great big clue that it’s a papillary carcinoma).

Metastatic calcification
This type of calcification happens when there is hypercalcemia (this is the one thing I could remember!). It happens in normal tissues (not necrotic tissues, like dystrophic calcification). It doesn’t happen in all cases of hypercalcemia – only some. It may occur widely throughout the body, hence the term “metastatic.” I wish they would have picked a different term, because metastatic makes you think “malignant tumor” and that could make you think that this is the type of calcification you see in papillary carcinomas, which is not the case.

The process seems to affect mostly interstitial tissues of the gastric mucosa, kidneys, lungs, systemic arteries and pulmonary veins. It turns out that all of these tissues excrete acid, and therefore have an alkaline internal component, which is susceptible to calcification. You can see either amorphous deposits or discrete crystals, just like in dystrophic calcification. The deposits are formed of calcium phosphate crystals too, just like in dystrophic calcification.

So what does it mean if you see metastatic calcification? Mostly, it just means the patient is hypercalcemic, and you have to figure out why. Is it an elevated parathyroid hormone, or destruction of bone, or what? Usually the deposits in and of themselves don’t do much damage (though if you get a ton of metastatic calcification in the lung or kidney it can impair function).

Bottom line
Both types of calcification consist of calcium phosphate crystals. The big difference is that dystrophic calcification occurs in damaged tissue, and metastatic calcification occurs in normal tissue in the setting of hypercalcemia. Hey, I just thought of something: dystrophic = dead/damaged! Wish I would have thought of that in med school.



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24 Responses to Dystrophic vs. metastatic calcification

  1. ali says:

    Dr. Krafts, It seems like you are having fun explaining this concept. I wonder why. I WISH I HAD TEACHERS LIKE YOU IN MEDICAL SCHOOL. PATH WOULD BE MUCH MORE FUN. THANKS.

  2. Lindsey says:

    Dear Dr. Krafts,
    First of all, HUGE fan of your site as well as your books and study guides.

    Metastatic vs dystrophic is something that has confused me. Would you say that the metastatic calcification in renal osteodystrophy, however, isn’t due to hypercalcemia but more because of hyperphosphatemia (a secondary hyperparathyroidism) with low calcium in this case?
    Thank you,

  3. Kristine says:

    Thanks, Lindsey! I’m not sure what you are referring to when you say metastatic calcification in renal osteodystrophy…I’m not aware of that phenomenon. In renal osteodystrophy, you’re right, the changes (mostly bone erosion) are due to hyperparathyroidism. As the kidney fails, it retains phosphate and pees out more calcium. The lower serum calcium stimulates the parathyroids to make more parathyroid hormone, which stimulates (among other things) osteoclasts to chew up bone.

  4. ippu says:

    nice explanation sir….

  5. med student says:

    I just found the answer.

    This article came out two days ago from the New England Journal of Medicine:

    Although metastatic calcification is USUALLY seen with hypercalcemia, it’s not the hypercalcemia directly that is the cause of the process, as much as it is the calcium-phosphate product. In chronic renal disease and secondary hyperparathyroidism, although serum calcium can be low or normal, serum phosphate is high, so the solubility product is breached, leading to the diffuse (metastatic) calcification.

    So to help address Lindsey’s question, pathologies associated with high phosphate (renal failure in the setting of hyperparathyroidism) can lead to metastatic calcification.

  6. Kristine says:

    Thanks so much for posting that! Smart community here.

  7. Edwards Nkechi says:

    thank you so much, I also made that same mistake of thinking psammoma bodies in thyroid papillary carcinoma was metastatic calcification because of the word metastatic. Wish I knew about this website back then in med school things would have been a lot easier

  8. lanre says:

    Thanks sir! I really had a bagful of wahala getting those things sticks# its simple n comprehensive now!

  9. Neha Rahatekar says:

    Very nice explanation….one of d easiest ways to remember….thanks..

  10. Dr reema says:

    I ws so confused while atempting mcqs
    related to calcification while giving
    part 1 exam.u hav made it so easy thnxxxc

  11. David says:

    Oh, I am writing final med grad school pathology in 2 days time and I know that if you were our lecturer I had a much better chance of passing! We’re using the USA curriculum and I basically have to self-teach from Robins!

  12. Kristine says:

    Oh boy. Well, at least you have a good book!! Best wishes to you πŸ™‚

  13. Yuuki says:

    thank’s sir finally i can catch up on our topic… thank’s a lot your explanation is very simple whereas anyone can prettily understand πŸ˜€

  14. duracell19 says:

    thanx for this topic. its really helpful. i just wanted to ask that what is the most common site for metastatic calcification? for example if best choice question comes in exam then what should we mark lungs or kidney?
    plz do reply, thanx πŸ™‚

  15. Kristine says:

    Kidney would be the number one place. Other places include stomach, lung, myocardium and blood vessels.

  16. Nursyafiqah hanafiah says:

    Hi dr krafts. Thank you so much for the notes😁😁😁 finally i understand the concepts of pathologic calcification

  17. Venessa says:

    I’ll ditto that first comment. If only there were more teachers that wanted to “share the knowledge & their little ways of remembering things” πŸ˜‰ as you have kindly done so. It seems that more educators aren’t quite open to discussions – just rattle off a power point, no whiteboard scribble to help explain – and then there’s an exam! Job done. Next please.

  18. Kristine says:

    Thanks, Venessa πŸ™‚ Yeah, I know what you mean…sometimes teaching is seen more as an unpleasant task to get through and then get on to more lucrative or job-promoting tasks. It’s too bad.

  19. Ahmed says:

    Nice presentation

  20. Peace says:

    Thank you so much this was really helpful. It contained keywords.

  21. Thomas Ndeule says:

    Thanx for very good explanation .

  22. George says:

    Just fine by me.Well deserve kudos for make pathology a mere friendly to learn.

  23. Thanks a lot! (y)
    I wish I could have known to this site before… πŸ™‚

  24. AG says:

    Thanks Kristine, very helpful!

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