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.
