A nail biopsy needs to be softened before it can be properly sectioned for microscopic examination. A variety of chemicals can be used to break down the disulfide crosslinks in the keratin matrix that make the nail hard.


The nail must first be fixed in formaldehyde, since treatment before fixations results in loss of the nail plate and bed.


Options after fixation:

(1) treatment of the nail prior to processing

(2) treatment of the tissue in the paraffin block prior to sectioning

(3) combination of treatments #1 and #2


Treatment of nail biopsy prior to processing - one of the following:

(1) 25% HNO3 (nitric acid) for 1 hour (may be inadequate for thick nails)

(2) 10% KOH for 30 minutes


Treatment of paraffin blocks prior to sectioning - one of the following:

(1) sulfhydryl compound (thioglycollate) in commercial depilatory or hair wave lotions, for 1 hour at room temperature

(2) 1% aqueous polysorbate 40 (Tween 40, polyoxyethylene sorbitan monopalmitate) at 4°C for 1 hour


Combined method using both approaches involves:

(1) First treating the nail with 10% KOH for 30 minutes.

(2) Then treating the paraffin block with 1% aqueous polysorbate 40 at 4°C for 1 hour.


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