When the presence of calcium was not expected, such as in kidney, lung, prostate, or skin tissue but is revealed during trimming, a paraffin-embedded tissue can be "surface decalcified" prior to microtomy. Also, bone that has already been decalcified, may need more time in decal solution and surface decal may be employed in such cases as well. Surface decalcification allows the decalcifier to penetrate a small distance into the block and dissolve the calcium.
Steps for surface decalcification of paraffin-embedded tissue blocks:
- Course face the tissue block to expose the entire tissue (if possible).
- Place the tissue block in preferred decalcifier (typically HCl) for 30-60 minutes.
- Rinse the block in water and blot dry.
- Place on ice.
- Section as usual, but keep in mind that only the surface was decalcified. Deeper sections may need to be decalcified.
