Flash Freezing of Mohs Micrographic Surgery Tissue Can Minimize Freeze Artifact and Speed Slide Preparation

BACKGROUND In Mohs micrographic surgery, excised tissue is traditionally prepared for cryotomy by freezing in the cryostat's refrigerated chamber. Any delay may cause drying artifact and tissue autolysis and affect slide turn around time (TAT). Flash freezing is used in frozen section processing of general pathology specimens to expedite TAT and enhance tissue histology by minimizing ice crystal formation (freeze artifact). DESIGN This was a pilot quality improvement study to compare flash freezing of Mohs sections with the traditional method of freezing in the cryostat. Mohs layers divided into at least two sections (one set) were enrolled. One half was flash frozen in an isopentane histobath (-56 to -62 degrees C); the other half was frozen in the cryostat (-27 to -30 degrees C). RESULTS Forty-one sets were enrolled. Average cryostat and histobath freeze times (range) were 144 seconds (90-240 seconds) and 22 seconds (15-40 seconds), respectively. Laboratory technicians felt that it was easier to achieve smooth, wrinkle-free sections in histobath frozen tissue in 90% of tissue sets. Physicians favored histology from flash frozen specimens (range 65-85%) over the traditional method of cryostat freezing. CONCLUSION Flash freezing in a histobath produced a more rapidly opacified (frozen) specimen ready for cryotomy, expediting slide TAT. Tissue histology also demonstrated better quality and minimized freeze artifact.