Bill Moore's Commentary:
How to Embed Specimens.



      EMBEDDING FOR SURGICAL MARGINS. I have a personal ritual for embedding tissue for surgical margins. As with religious rituals, I have a rationalization for my behavior, but this may be difficult to justify with experimental observation. Every tissue block for surgical margins should be a maximum of 2 mm thick, and has two edges: the edge facing the patient (EFP) and the edge facing the main specimen (EFS). In my view (justified below), the FIRST SECTION evaluated by the pathologist should be as close as possible to the EFP.

      Ideally, I cut margins on crisp, well-fixed tissue (fixed at least a few hours in formalin; colons and other major specimens fixed overnight). In order to guide the histotechnologist to embed the tissue correctly, I place a small drop of eosin on the EFP. I make a note on my histology paperwork: START CUTTING AT RED SURFACE. I mention this in person to the histotechnologist, if necessary. Eosin survives all the steps in the embedding process, and is readily visible on the paraffinized tissue.

      Theoretically, the EFP is the TRUE MARGIN. That is, if there is cancer in the EFP, then my report reads: SURGICAL MARGIN OF RESECTION IS INVOLVED BY TUMOR. There may be a further explanatory comment regarding WHICH margin is positive. In my department, we insist that the surgeon provide enough orientation of the specimen such that the anatomical orientation is always known to the pathologist. Fortunately, pathologists have enough power in our institution that we can report recalcitrant surgeons to the Surgical Case Review Committee. In many private community hospitals, where the surgeons outrank the pathologists, an insistent pathologist soon becomes an unemployed pathologist.

      If the EFP section is negative for tumor, but deeper sections (which may be cut for a variety of reasons), my report reads: SURGICAL MARGIN OF RESECTION IS UNINVOLVED BY TUMOR. SEE COMMENT. Then, in the comment, I explain that, while the TRUE surgical margin is TECHNICALLY free of tumor, for all intents and purposes, tumor extends to within one mm of the true margin. For some margins, this distinction makes a difference to the surgeon's followup care. For example, for a skin cancer resection in an area with considerable redundant skin and no cosmetic issues (e.g., a basal cell carcinoma of the arm or back), the surgeon will cut an additional, wider resection margin. On the other hand, for a skin cancer resection in an anatomically or cosmetically significant area (nose, eyelid, etc.), the surgeon will follow the patient with clinic visits, and only reoperate if there is a clinically apparent recurrence.

      As I suggested above, much of this ritual is like counting angels on the head of a pin, without much experimental justification. Nevertheless, I believe that rituals, namely, repetitive behaviors, have an important place in pathology. If nothing else, if you have to investigate a bad outcome on a patient, then you know how you performed a particular step, because you ritually ALWAYS perform that step in a certain way.

      There is a considerable literature regarding margins in basal cell carcinoma of the skin [ref. 1]. In general, a basal cell carcinoma with a NEGATIVE MARGIN has a 20% chance of recurrence, presumably because of tiny tumor rootlets that are essentially invisible to the pathologist (especially in MORPHEA type basal cell carcinoma). On the other hand, a basal cell carcinoma with a POSITIVE MARGIN has only a 50% chance of recurrence, presumably because of traumatic tissue necrosis immediately beyond the surgical margin. Thus, there is a STATISTICAL BENEFIT in obtaining pathologic margins, but NOT an ABSOLUTE BENEFIT.



REFERENCES.



  • 1. Seidman JD, Berman JJ, Moore GW.
    Basal cell carcinoma: importance of histologic discontinuities in the evaluation of resection margins.
    Mod Pathol. 1991 May;4(3):325-330.
    Abstracted in Yearbook of Pathology and Clinical Pathology, eds., Gardner WA jr, Bennett BD, Cousar JB, Garvin AJ, Worsham GF, St. Louis: Mosby, pp. 189-190, 1993.
    PMID: 2068058; UI: 91296724.
    PubMed Entry
    Full Text of Article

  • 2. Prophet EB, Mills B, Arrington JB, Sobin LH.
    Laboratory Methods in Histotechnology, pp. 33-38.
    1992: Armed Forces Institute of Pathology, Washington, DC. 20306-6000.
    ISBN: 1-881041-00-X 1992.

    Last Updated: October 10, 1999.