5.1. Gross Examination
In theory, a mass is clearly identifiable and the distance to various resection margins measurable. In reality, often the mass is irregular with ill-defined tentacles cast out in different directions (). An advantage of gross examination is that it is a rapid method of assessing margins and is useful in identifying grossly transected tumor and close invasive tumor. In the setting of intraoperative consultation, a grossly close or positive margin can be rapidly communicated to the operating room while additional margin assessments are completed. A grossly negative margin has little predictive value unless the margin clearance is several centimeters and the patient does not have extensive DCIS, multifocal disease or invasive lobular carcinoma.
On left, gross inspection in theory: A clearly defined mass measurable from the margins. On right: Reality, an ill-defined mass with indistinct borders and irregular specimen edges.
5.2. Image or Faxitron Analysis
Many institutions confirm resection of lesions using specimen imaging. Conventionally this is a single dimension X-ray with compression of the excision specimen (). A smaller set of institutions incorporate 2-dimensional digital specimen mammography (Faxitron) without specimen compression. This may be followed with a second specimen mammogram of the serially sectioned specimen (). The Faxitron appears to be better than conventional radiography at delineating microcalcifications and parenchymal distortions near margins, thereby enabling pathologists to select tissue for microscopic assessment. In the setting of intraoperative consultation, immediate reexcisions can be performed resulting in tumor-free resection margins at the time of the primary surgery [24
]. The sensitivity of the Faxitron appears to range from 78.6–85.6% for magnification of 1.0–2.0
1.0, with a specificity of 100% [26
]. However, if the Faxitron equipment and the ability to interpret the images is not housed within the pathology suite, there can be significant time delay with its use in intraoperative consultation.
Specimen radiograph of a wire localization excission taken without compression. The cluster of abnormal calcifications is present but is not at the edge of the specimen. Often a second image is taken after rotating the specimen 90 degrees.
Figure 6 Serially sectioned excision specimen and its Faxitron X-ray. The X-ray image shows a stellate mass in the sixth section from the left with fingers extending very close to the surgical margins. (Image courtesy Dr. A. Sahin, MD Anderson Medical Center). (more ...)
5.3. Touch Imprints or Smears of Margins
An imprint (touch) or a scraping of the specimen surface, placed on glass slides and stained using either hematoxylin and eosin or diffquick, can be used to evaluate for tumor cells in a specimen margin (). This method is employed only in the setting of intraoperative consultation. The advantage of this method lies in the fact that it does not alter the specimen, which can be later imaged, fixed, and/or sectioned. The disadvantages are many: the requirement for multiple imprints, the associated time consumption, the dependency on close visual inspection of the specimen, the ability to only detect transected disease, lower sensitivity, and the inability to measure the width of clearance. Klimberg et al. originally reported a sensitivity, and specificity of 100% for the use of touch preparation cytology in the evaluation of surgical margins in breast cancer [27
]. The sensitivity and specificity of the method in reexcision margin assessment, however, is reportedly only 75% and 82.8%, respectively, producing a PPV of 21.4% and a NPV of 98.2% [28
Figure 7 Method of obtaining touch imprints and/or smears. A slide is pressed against the surface of an excision specimen or the surface is scraped and smeared on a slide. The slide is then stained and examined for malignant cells. The microscopic image at the (more ...)
5.4. Intraoperative Frozen Section (FS)
Mammary tissue is notoriously technically difficult to cryosection because of its adiposity. Freezing also introduces tissue artifact in the form of architectural distortion and resistance of adipose tissue to sectioning. In addition, if the tissue submitted for evaluation is more than one centimeter in largest dimension, there is the added risk of sampling error. This method therefore is not popular amongst most pathologists. Surgeons, however, like the method because it enables rapid microscopic examination of tissue during surgery and it can be used to determine the extent of surgery to be performed in a single operative setting. However, the use of frozen section for multiple margin assessment is time consumptive and adds significantly to operating time. In order to provide good turnaround for multiple margin assessments, a pathology frozen section suite would have to be equipped with multiple cryosectioning units and have reserves in both equipment and personnel so as not to impact other surgeries. More importantly frozen section alters the appearance of tumors, particularly ductal carcinoma in situ and infiltrating lobular carcinoma and benign lesions such as intraductal papillomas and sclerosing adenosis (). The ability to read through the artifact and not call a benign lesion malignant or a malignant area benign is dependent on the skill and experience of both the pathologist and the entire frozen section staff.
Frozen section slide showing thermal artifact, which obliterates microscopic details that a pathologist needs to diagnose carcinoma. The area bottom center on the edge of the tissue is ductal carcinoma in situ that has been transected in a margin.
Cendan and his group performed a retrospective analysis of FS margin accuracy compared to permanent sections and showed an 84% concordance per case, with 24% of the patients requiring immediate reexcision intraoperatively of the lesion and approximately 20% of patients needing second surgery due to false negative margins. Expectedly, invasive lobular carcinoma and DCIS cases had higher rates of false negative FS margins. In addition, 51.2% of all patients with positive margins had at least one false-negative margin on either the primary or secondary excision [26
Osborn et al. compared the cost-effectiveness of routine FS analysis of breast margins against reoperation for positive margins assessed by routine examination of the resected specimen. Their experience has shown that the use of FS for margin assessment with the attendant increased operative time provide cost savings only when the reexcision rates are greater than 36% [29
]. The use of intraoperative assessment of margins is driven in part by patient demographics. Institutions which have a large patient population that travels long distances for surgical treatment will spend more resources in attempting to achieve tumor-free margins at primary excision to avoid second surgeries than medical centers whose patients are local and who can readily return for a second procedure if needed. The expense and inconvenience of patients having to return from great distances is balanced against the greater expenditure of operating room time.
5.5. Shave Margins
Surgically, a shave margin is a thin piece of tissue obtained by shaving the surface of a lumpectomy cavity or other excision surface. This tissue will have two surfaces of interest: the original margin and the new margin surface. These two surfaces are differentially inked to maintain identification of the two margins. Most shave margins are large enough to require serial sectioning with submission of multiple tissue sections for microscopy to completely assess for presence or absence of disease. The pathologist can trace disease, if present, from the original margin to the new margin. Any disease present can be measured for distance from the “final” margin.
A shave margin taken by a pathologist is a very thin slice of tissue from a margin surface in question and is usually a size that can be frozen for microscopic intraoperative examination or placed directly in a tissue-processing cassette. Any tumor present in the section examined would indicate a positive margin (). In the intraoperative setting, relatively larger surface areas can thus be examined compared to that of a perpendicular section through a margin, providing a yes or no answer. Disadvantages of a shave margin include difficulty in obtaining a shave of a soft surface and in maintaining tissue orientation. The nature of the section also precludes measurement of the clearance of a tumor from a margin. Pathologic shave margins for permanent section are most commonly used to assess margins that are distant from a tumor and are required for completeness of reporting margin status.
Figure 9 Method of obtaining a (pathologic) shave margin from a specimen. A thin piece is taken from the surface of a specimen and either frozen or processed for microscopy. The slide and microscopy show tumor present in the tissue. This would be considered a (more ...)
5.6. Perpendicular Margins
A perpendicular margin is a tissue section taken perpendicular to the margin surface. This type of margin section allows a pathologist to not only determine if a margin is positive or negative, but more importantly measure clearance of tumor from the margin. An excision specimen will be inked, either a single color or in multiple colors if the specimen is oriented and serially sectioned perpendicular to the longest axis of the tissue (). This readily allows measurement of margin clearance both grossly and microscopically and relationship of the tumor to various margins (). The drawback is that only a representational surface area can be examined from each section. Also, large, soft specimens are not as amenable to production of serial thin intact sections. This drawback can be mitigated by fixing a specimen utilizing special fixative with hardening agents, and/or chilling a specimen prior to sectioning. This methodology is preferred by pathologists because it allows assessment of clearance as well as tumor size, both very important factors in predicting residual disease and recurrence.
(a) Different colored inks placed on the surface of a specimen maintain the orientation during sectioning and processing. (b) Serial sectioning of inked specimen showing the different inks on the edges of the slices.
Close up of a perpendicular section of margins with tumor. The tumor is distant from the margin at the top of the image, but very close to a margin at the bottom right of the image.
In the practice setting, pathologists will employ combinations of the above techniques to provide greater accuracy in determining margin status and the risk of residual disease being left in a patient. Good communication with the surgeon concerning how s/he is excising a lesion, whether there is additional tissue submitted separately for “margins” and the size and type of carcinoma are key. Meticulous gross examination and/or image assessment of the tissue will discover areas suspicious for tumor involvement. Such areas will be the focus of microscopic examination, both in the frozen section suite and at microscopic “sign out” of the specimen. The pathologist's goal in margin assessment is to provide an accurate assessment of margin status and accurate estimate of the risk of residual disease in each and every patient.