Variable fidelity of tissue-marking dyes in surgical pathology

Pathology specimens often contain important margins that must be identified from gross examination of specimens through to microscopic examination. Commonly, unique colours of tissue-marking dye (TMD) are applied to each margin, which facilitates both macroscopic and microscopic identification. Various techniques have been described, but the colour endurance and fidelity of TMDs following special tissue processing have not been addressed. The aim of this study was to evaluate the performance of various TMDs through decalcification and immunohistochemistry (IHC) protocols.

Samples of TMDs from two manufacturers and acrylic artists' inks were obtained in seven colours and applied to excess non-diagnostic surgical pathology tissue. Tissues were subjected to a decalcification protocol or directly processed in a routine fashion. The presence and colour of TMD or ink were assessed on routine H&E sections and following IHC. Of the colours that reliably survived routine processing, loss of colour and colour change following decalcification and IHC protocols were seen with one manufacturer's product.

TMD may lose or change its colour during special tissue processing. This previously unreported artefact may lead to potentially serious errors in margin assessment and reporting. Laboratories should evaluate TMDs and inks through routine processing, decalcification, and IHC protocols, to ensure colour endurance and fidelity.