¹Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, TX
²Department of Dermatology, Texas Tech University Health Sciences Center, Lubbock, Texas
³Department of Dermatology, Baylor University Medical Center, Dallas, Texas
⁴Epiphany Dermatology, Dallas, Texas
⁵Department of Dermatology, University of Texas at Southwestern, Dallas, Texas
⁶Texas A&M University College of Medicine, Dallas, Texas

*Address for Correspondence: Stanislav N. Tolkachjov, Department of Dermatology, University of Texas at Southwestern, Dallas, Texas USA. E mail Id: Stan. tolkachjov@gmail.com

Submission:22 July, 2024 Accepted:15 August, 2024 Published:20 August, 2024

Copyright: © 2024 Kichena S, et al. This is an open access article distributed under the Creative Commons Attri-bution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Keywords:Clearing Agent; UV Mounting Medium; UV Light; Xylene; Xylene Substitute

Xylene and xylene substitutes are commonly used as clearing agents when processing tissue samples during Mohs micrographic surgery (MMS). However, there are several concerns with these solvents. Xylene is expensive, malodorous, and can be toxic depending on exposure levels. While xylene substitutes are less toxic, some of these are more expensive than xylene itself or do not biodegrade easily and require specific waste disposal. Here, we discuss an alternative using Ultraviolet (UV) Clear PermaSlip Mounting Medium and a UV light. This technique is advantageous in that it is non-toxic, has no odor, and does not have the significant costs of purchase and disposal that xylene and xylene substitute typically have. However, we found this technique can add up to 2 minutes to the process, and more importantly, may reduce the quality of the slide. Upon slide review with this method, we found more intracellular lacunae artifact with keratinocytes in the epidermis compared to the same tissue on consecutive cuts where traditional xylene substitute was used. Future studies could look at ways to minimize lacunae with this method. Ultimately, we must weigh the advantages and disadvantages of using a UV mounting medium and UV light and utilize our different options to provide the best quality patient care

MMS: Mohs Micrographic Surgery; UV: Ultraviolet

MMS is a specialized form of skin cancer surgery resulting in a nearly 100% cure rate while minimizing lost tissue and is particularly useful in cosmetically sensitive areas [1]. The surgeon first removes a thin layer of skin from the skin cancer. The tissue is then frozen, cut into thin slices, stained, and evaluated under a microscope for circumferential and deep tissue margin clearance of the skin cancer. If the margins are not clear, the process is repeated until they are clear [2]. During this tissue processing, speed and efficiency are pertinent in providing quality care. The histologicfrozen-tissue stains commonly used are generally based on preference and training, but three commonly used stains are toluidine blue, thionine, and hematoxylin &eosin [3]. Today, many Mohs clinics use automated slide stainers. Afterwards, a clearing agent is used to make biological tissues transparent while preserving tissue structure, allowing for visualization of the tissue under a microscope [4].

Currently, there are three main categories of tissue clearing techniques: solvents, hyperhydration, and hydrogel embedding techniques [4]. However, hyperhydration and hydrogel embedding technique are very time consuming and can take days. One such solvent used as a clearing agent is xylene. Xylene is an aromatic hydrocarbon commonly used during tissue processing in MMS. Advantages of xylene usage include that it is biodegradable, noncorrosive, nonflammable, soluble in alcohol and mounting media, reasonably fast drying, and doesn’t leave a residue. However, xylene is also expensive, malodorous, and can be toxic depending on exposure levels. Some literature even recommends the use of a fume hood or some local exhaust ventilation in addition to personal protective equipment to reduce toxicity [5] .MMS labs now commonly use solvents such as Naphthenic solvent and d-limonenes chemicals that can be used a xylene substitute, but some of these are more expensive than xylene itself or do not biodegrade easily and require specific waste disposal.

As a result, in our clinic, we trialed the use of UV Clear PermaSlip Mounting Medium and a UV light as a new clearing agent [Figure 1]. Using the Leica ST4020 linear slide stainer, we utilized a combination of alcohol, H2O, Gill’s Hematoxylin I, Gill’s Hematoxylin II, Toluidine blue, and Eosin Y during the staining process [Figure 2]. In order to use this mounting medium, the slide must first dry after going through the staining process. Then a small amount of the mounting medium is applied to the slide and cover slipped. Finally, the slide must sit under a UV light for approximately 30 seconds. This whole process can take up to 2 minutes.

We found that this technique is advantageous in that it is nontoxic, has no odor, and does not have the significant costs of purchase

and disposal that xylene and xylene substitute typically have. However, we found this technique can add up to 2 minutes to the process, and more importantly, may reduce the quality of the slide. Upon slide review with this method, we found more intracellular lacunae artifact with keratinocytes in the epidermis [Figure 3] compared to the same tissue on consecutive cuts where traditional xylene substitute was used [Figure 4]. These intracellular lacunae are likely the result of focal evaporation and are important as melanocytic lesions, some inflammatory conditions, and extramammary Paget’s disease may be confused with this artifact.

We present another viable clearing method that can be utilized in MMS tissue processing. It is important to weigh the advantages and disadvantages of using a UV mounting medium and UV light in comparison to xylene or xylene substitutes. For example, in a clinic trying to cut the use of xylene substitutes or cost, UV mounting medium in conjunction with a UV light may be beneficial. Future studies could look at ways to minimize lacunaewith this method. Drying the slides for a longer duration, using a different drying method, and/or changing the amount of time spent under UV light may reduce this artifact. Ultimately, we must utilize our different options toprovide the best quality patient care.

Dr. Tolkachjov is an investigator and speaker for Bioventus and CASTLE and advisory board member for Illumisonics. Other authors have no relevant conflicts of interest to declare and did not receive any grants or funding for this project.