SURGICAL GEM

Direct Transfer of Curettings to Cryostat Chuck in Mohs Micrographic Surgery DAVID A. KIST, BA CHRISTOPHER B. ZACHARY, MB, MRCP

I n t h e routine handling of M o h s specimens t h e curetted first layer is integral to t h e process of t u m o r identification. Small specimens m a y be smeared inadvertently on filter paper or gauze or e v e n lost between t h e operating room and laboratory. An efficient method forprocessing small curetted specimens has been devised that bypasses t h e use of a tissue tray. T h i s method improves tissue morphology and saves time. J Dermatol Surg Oncol 1992;18:226- 228.

seconds, the partially frozen curettings will be retained by the frozen OCT. Alternatively, the curettings may be deposited on the OCT using the rear end of a coton-tipped applicator. Standard 6-pm sections are taken subsequently from the specimen and processed by standard

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n the course of Mohs micrographic surgery it is standard practice to debulk the tumor as part of the first Mohs layer. This is performed generally with a curette. Histologic examination of these curettings confirms tumor location and also indicates tumor type. The curettings are normally placed on a tissue tray lined with filter paper or gauze. While this presents no problem with the majority of the larger specimens, the smaller curettings tend to dry up, become smeared on filter paper, or become caught in the gauze fibers, making subsequent recovery difficult. We have introduced two modifications in our laboratory that have improved significantly the quality of small curetted sections.

Materials and Methods

Figure 1 . Small volume curettings are often realized as a part of Mohs surgery.

Figure 2. Direct transfer of specimen onto a labeled cryostat chuck.

When only small quantities of curettings can be realized (Figure l), they are transferred immediately onto frozen optimal cutting temperature compound (OCT) on a prelabeled cryostat chuck (Figures 2 and 3). Transfer of this specimen may be accomplished by the “curette catch” technique. This is achieved by pressing the tumor laden open part of the curette onto a frozen OCT covered - 30C cryostat chuck. By lifting the instrument off after 2 to 3 From the Department of Dermatology, University of Minnesota, Minneapolis, Minnesota. Address reprint requests to: Christopher B. Zachary, ME, MRCP, Department of Dermatology, University of Minnesota, Box 98 Mayo Building, 420 Delaware Street S.E., Minneapolis M N 55455.

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Figure 3. Entire curetted specimen transferred without smearing.

Figure 4 . 4) With "curette catch" technique, good localization of small volume curettings is achieved. (HBE, original magnification X 40.) B) Excellent tumor morphology is maintained with minimum artifact. (HBE, original magnification

x 200.)

KIST AND ZACHARY CURETTINGS: DIRECT TRANSFER TO CRYOSTAT CHUCK

Figure 5. Cutting around curetted specimen on filter paper.

Discussion Vertical sections of diagnostic biopsies are obtained normally prior to Mohs surgery. However curettage is employed generally in the first Mohs layer to debulk the tumor and define the clinical borders. While this often provides ample tumor tissue for examination, there are times when only minute quantities of curettings can be obtained. This article describes a simple approach to improve significantly one's ability to handle small-volume curettings from Mohs patients. There are three main benefits from this technique. The first is the avoidance of possible contamination of other Mohs sections with tumorous curettings. The second is that the entire curettings may be cut and examined. The third is that, left for more than a few minutes, small curettings tend to dry up more quickly than larger Mohs layers. Curettings are often processed

A Figure 6. Undisturbed curetting on filter paper.

B

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Figure 7 . Embed filter paper flat onto chuck, parallel to cryostat blade.

after the intact Mohs layers, and tend to be left exposed longer to the air. Immediate transfer to frozen OCT avoids any desiccation. Excellent cryostat sections may then be obtained (Figure4, A and B). To use the technique

effectively and to avoid potential problems 1)the laboratory must be adjacent to the procedure room and 2) the frozen OCT must be labeled with an appropriate marker to avoid confusion when multiple specimens are involved. An alternative method for processing curettings that have already been placed on filter paper is to cut around them, including the filter paper, and to embed this in its entirety in OCT (Figures 5 - 7). Cryostat sections are cut parallel to the paper, carefully avoiding cutting into the paper and dulling the blade. These methods have enabled our laboratory to identify

References 1. Picoto AM, Picoto A. Technical procedures for Mohs fresh tissue surgery. J Dermatol Surg Oncol 1986;12:134-8. 2. Rustad OJ, Kaye V, Cerio R, Zachary CB. Postfixation of cryostat sections improves tumor definition in Mohs s q e r y . J Dermatol Surg Oncol 1989;15:1262-7.

Direct transfer of curettings to cryostat chuck in Mohs micrographic surgery.

In the routine handling of Mohs specimens the curetted first layer is integral to the process of tumor identification. Small specimens may be smeared ...
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