Evaluation of marking materials for cutaneous surgical margins

Microscopic evaluation of the margins of excised cutaneous neoplasms is of paramount importance for determining that neoplastic tissue does not extend to the excision borders. Dyes or pigments that indelibly mark the tissue should be more reliable than sectioning techniques or suture markers for identifying the surgical margins before and after tissue processing. We evaluated 5 pigments to select a material that could be rapidly applied by surgeons, and readily identified on histologic section by the pathologists. Twenty normal canine skin specimens were assigned to each of 5 groups. Each group was treated with artists' pigments in acetone, India ink in acetone, alcian blue, typists' correction fluid, or a commercially available marking kit. Ten specimens within each group were marked before formalin fixation, and 10 were marked after fixation. Application properties, fixation and processing properties, and microscopic characteristics were evaluated for each material. Application properties were acceptable for all marking materials on unfixed specimens, and for alcian blue, India ink in acetone, and correction fluid on fixed specimens. Fixation and processing properties were acceptable for all materials except correction fluid. All marking materials survived fixation and processing, and colors were readily visualized under the microscope. Microscopic characteristics were acceptable for alcian blue, India ink in acetone, and the commercial kit. Overall, alcian blue was the best marking material, with India ink in acetone and the commercial kit also acceptable. Correction fluid and artist' pigments in acetone were not acceptable because pigment fragmentation and incomplete tissue coverage hindered microscopic evaluation of resection margins.