REVIEW ARTICLE
Pathologic Evaluation of Sentinel Nodes Jane L. Messina, MD*† and Marilin Rosa, MD*‡ Abstract: Optimal utilization of sentinel node biopsy in the care of cancer patients requires cooperation between the radiologist, surgeon, and the pathologist. Accurate pathologic diagnosis of the sentinel node is central to correct staging, optimal treatment decisions, and precise prognostication of patients with melanoma, breast, colorectal, lung, and gastric cancer. Intraoperative handling, gross dissection, and histologic/ immunohistochemical evaluation techniques are all key components of this process. Although not currently part of routine handling, newer molecular techniques may potentially add to the valuable information gained from evaluating sentinel node specimens. Key Words: Sentinel node, melanoma, breast cancer, colorectal cancer, lung cancer, gastric cancer, immunohistochemical (Cancer J 2015;21: 33–38)
T
he results of sentinel node surgery are central to disease management in a variety of clinically localized malignancies. Since the technique was introduced by Donald Morton and colleagues 22 years ago,1 it has been applied to a variety of tumors, chiefly those of skin, breast, lung, and upper and lower gastrointestinal tract. While the same general intraoperative handling and gross dissection paradigms apply to sentinel nodes removed in most of these scenarios, there are also techniques and protocols distinctive to each of these situations. This review covers the principles of routine pathologic evaluation of sentinel nodes in the most commonly applied clinical situations, emphasizing techniques of gross evaluation, dissection, and the applicability of immunohistochemical and molecular evaluation of this small piece of tissue that is so central to the management of an everincreasing number of malignancies.
Overview of Specimen Handling Intraoperative Evaluation Sentinel lymph nodes (SLNs) are identified intraoperatively by the visual presence of isosulfan blue dye and/or radioactivity, usually technetium Tc 99m, the latter assessed by handheld gamma probe. There is emerging use of fluorescent-labeled dyes such as indocyanine green, especially in gastric, lung, and colorectal cancer.2 The definition of a sentinel node is any node that is palpably abnormal, blue-stained, and/or radioactive, generally defined compared with background or to the hottest node removed. Even with standardized definitions, surgeons will differ in how many nodes they retrieve in a given case. In most cases, the lymph nodes are individually removed, numbered, and submitted to pathology by the surgeon. In the case of gastrointestinal malignancy, the lymph nodes may be intraoperatively marked by the surgeon with a suture and removed en bloc with the tumor resection specimen.3 There are reports that radioactivity and/or blue dye may be From the H. Lee Moffitt Cancer Center, Departments of *Anatomic Pathology, †Cutaneous Oncology, and ‡Women’s Oncology, University of South Florida Morsani College of Medicine, Tampa, FL Reprints: Jane L. Messina, MD, H. Lee Moffitt Cancer Center, 12902 Magnolia Dr, Tampa, FL 33612. E-mail: [email protected]. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 1528-9117
localized to smaller subregions of the SLN itself, a phenomenon we have labeled the “hot spot.” An early report by Haigh et al4 used suspended carbon particles (India ink) admixed with the blue dye to exploit this phenomenon in SLN from melanoma patients, and indeed significant colocalization of micrometastases and carbon particles was noted on pathology. However, this procedure did not gain widespread acceptance chiefly because of lack of Food and Drug Administration approval of the ink. There is ongoing research utilizing commercially available sterile permanent inks to indicate the location of the hot spot. This ink can be utilized by the surgeon to mark the area of greatest radioactivity and/or highest concentration of blue dye. Subsequent pathologic evaluation of the node should then ensure identification of this ink in permanent sections, which may theoretically increase the yield of micrometastasis identification. Rapid intraoperative identification of SLN metastases may allow the patient to avoid second surgery and treatment delays. While the survival impact of axillary lymph node dissection (ALND) has been called into question, especially in breast cancer, nonetheless there has been abundant investigation into the utility of frozen section and touch imprint cytology analysis. This has been most commonly advocated in breast cancer, where the higher incidence of SLN positivity could warrant the greatest impact, and has been most extensively studied in the United Kingdom. A 2003 survey of 240 units in the European Breast Cancer Network reported that 60% used intraoperative assessment, but revealed that standardized guidelines are not routinely used.5 Intraoperative immunohistochemical assessment of frozen sections using rapid staining for cytokeratin antibodies was less commonly used and was reported in 10% of laboratories using intraoperative assessment.5 A recent meta-analysis showed that although intraoperative frozen section has been found to be highly specific (99%–100%), it is less sensitive (57%–74%) for the detection of breast micrometastases.6 In melanoma, frozen section has been found to have similarly low sensitivity, with rates from 47% to 59% reported.7 While 1 group found a false-negative rate as low as 5.3%,8 this has not found widespread acceptance. Thus, because of concerns about tissue exhaustion and cryostat contamination, currently frozen section analysis is not advised in the detection of melanoma.9 In the setting of lung, gastric, or colorectal cancer, intraoperative evaluation of SLN assumes greater importance, but prospective studies are rare. A smallscale study of SLN identified in 64 patients with non–small cell lung carcinoma showed that a combination of frozen section and intraoperative imprint cytology (IIC) correctly identified at least 1 positive SLN in all 11 patients (17%) who subsequently had a positive SLN on permanent sections.10 However, 4 of these 11 patients had an additional positive SLN that was called negative on frozen section. Intraoperative imprint cytology gained widespread interest in the early 2000s as a rapid alternative to frozen section that can sample a broader area of tissue with no concerns for tissue usage. After touch imprinting 1 to several lymph node surfaces to a glass slide, a variety of staining techniques that have been used, including Giemsa/Diff-Quik staining, hematoxylin-eosin (H&E) staining, and additional rapid immunohistochemical staining. A pooled analysis of 7784 breast carcinoma patients comparing IIC to permanent sections found a sensitivity of 33% to 73%
The Cancer Journal • Volume 21, Number 1, January/February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
www.journalppo.com
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The Cancer Journal • Volume 21, Number 1, January/February 2015
Messina and Rosa
and specificity of 98% to 100%.6 The sensitivity in 1 large series was lower for lobular carcinoma (39%) than ductal carcinoma (56%), because of morphologic similarity with lymphocytes, and intraoperative immunohistochemistry (IHC) is particularly advocated for this histologic subset in groups performing IIC.11 In our practice, we recommend the use of IIC for all cases of breast SLN and do not perform frozen sections. While sensitivity for detection of micrometastasis is low, this limitation may not be crucial because ALND is not indicated in this subgroup. In melanoma, IIC has been shown to have a sensitivity of 33% to 61%, with a negligible false-positive rate. The sensitivity of IIC increases with the tumor stage, as high as 47% in patients with T4 lesions, and rises to 62% when metastases greater than 2 cm are present.12 Thus, it is acceptable to perform IIC in melanoma SLN and preferable to performing a frozen section, when metastasis is strongly suspected on gross examination.
Gross Dissection Techniques Standard gross dissection of all types of SLN begins with complete reporting of the anatomic location, SLN number, and, if indicated by surgeon, the presence or absence of blue dye, radioactivity counts, and hot spot. After proper fixation, any gross lesion, such as pigment or visible tumor, should be described and measured. Unless voluminous, the perinodal fat should not be dissected away, taking care not to disturb the lymph node capsule. If small (
Pathologic Evaluation of Sentinel Nodes Jane L. Messina, MD*† and Marilin Rosa, MD*‡ Abstract: Optimal utilization of sentinel node biopsy in the care of cancer patients requires cooperation between the radiologist, surgeon, and the pathologist. Accurate pathologic diagnosis of the sentinel node is central to correct staging, optimal treatment decisions, and precise prognostication of patients with melanoma, breast, colorectal, lung, and gastric cancer. Intraoperative handling, gross dissection, and histologic/ immunohistochemical evaluation techniques are all key components of this process. Although not currently part of routine handling, newer molecular techniques may potentially add to the valuable information gained from evaluating sentinel node specimens. Key Words: Sentinel node, melanoma, breast cancer, colorectal cancer, lung cancer, gastric cancer, immunohistochemical (Cancer J 2015;21: 33–38)
T
he results of sentinel node surgery are central to disease management in a variety of clinically localized malignancies. Since the technique was introduced by Donald Morton and colleagues 22 years ago,1 it has been applied to a variety of tumors, chiefly those of skin, breast, lung, and upper and lower gastrointestinal tract. While the same general intraoperative handling and gross dissection paradigms apply to sentinel nodes removed in most of these scenarios, there are also techniques and protocols distinctive to each of these situations. This review covers the principles of routine pathologic evaluation of sentinel nodes in the most commonly applied clinical situations, emphasizing techniques of gross evaluation, dissection, and the applicability of immunohistochemical and molecular evaluation of this small piece of tissue that is so central to the management of an everincreasing number of malignancies.
Overview of Specimen Handling Intraoperative Evaluation Sentinel lymph nodes (SLNs) are identified intraoperatively by the visual presence of isosulfan blue dye and/or radioactivity, usually technetium Tc 99m, the latter assessed by handheld gamma probe. There is emerging use of fluorescent-labeled dyes such as indocyanine green, especially in gastric, lung, and colorectal cancer.2 The definition of a sentinel node is any node that is palpably abnormal, blue-stained, and/or radioactive, generally defined compared with background or to the hottest node removed. Even with standardized definitions, surgeons will differ in how many nodes they retrieve in a given case. In most cases, the lymph nodes are individually removed, numbered, and submitted to pathology by the surgeon. In the case of gastrointestinal malignancy, the lymph nodes may be intraoperatively marked by the surgeon with a suture and removed en bloc with the tumor resection specimen.3 There are reports that radioactivity and/or blue dye may be From the H. Lee Moffitt Cancer Center, Departments of *Anatomic Pathology, †Cutaneous Oncology, and ‡Women’s Oncology, University of South Florida Morsani College of Medicine, Tampa, FL Reprints: Jane L. Messina, MD, H. Lee Moffitt Cancer Center, 12902 Magnolia Dr, Tampa, FL 33612. E-mail: [email protected]. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 1528-9117
localized to smaller subregions of the SLN itself, a phenomenon we have labeled the “hot spot.” An early report by Haigh et al4 used suspended carbon particles (India ink) admixed with the blue dye to exploit this phenomenon in SLN from melanoma patients, and indeed significant colocalization of micrometastases and carbon particles was noted on pathology. However, this procedure did not gain widespread acceptance chiefly because of lack of Food and Drug Administration approval of the ink. There is ongoing research utilizing commercially available sterile permanent inks to indicate the location of the hot spot. This ink can be utilized by the surgeon to mark the area of greatest radioactivity and/or highest concentration of blue dye. Subsequent pathologic evaluation of the node should then ensure identification of this ink in permanent sections, which may theoretically increase the yield of micrometastasis identification. Rapid intraoperative identification of SLN metastases may allow the patient to avoid second surgery and treatment delays. While the survival impact of axillary lymph node dissection (ALND) has been called into question, especially in breast cancer, nonetheless there has been abundant investigation into the utility of frozen section and touch imprint cytology analysis. This has been most commonly advocated in breast cancer, where the higher incidence of SLN positivity could warrant the greatest impact, and has been most extensively studied in the United Kingdom. A 2003 survey of 240 units in the European Breast Cancer Network reported that 60% used intraoperative assessment, but revealed that standardized guidelines are not routinely used.5 Intraoperative immunohistochemical assessment of frozen sections using rapid staining for cytokeratin antibodies was less commonly used and was reported in 10% of laboratories using intraoperative assessment.5 A recent meta-analysis showed that although intraoperative frozen section has been found to be highly specific (99%–100%), it is less sensitive (57%–74%) for the detection of breast micrometastases.6 In melanoma, frozen section has been found to have similarly low sensitivity, with rates from 47% to 59% reported.7 While 1 group found a false-negative rate as low as 5.3%,8 this has not found widespread acceptance. Thus, because of concerns about tissue exhaustion and cryostat contamination, currently frozen section analysis is not advised in the detection of melanoma.9 In the setting of lung, gastric, or colorectal cancer, intraoperative evaluation of SLN assumes greater importance, but prospective studies are rare. A smallscale study of SLN identified in 64 patients with non–small cell lung carcinoma showed that a combination of frozen section and intraoperative imprint cytology (IIC) correctly identified at least 1 positive SLN in all 11 patients (17%) who subsequently had a positive SLN on permanent sections.10 However, 4 of these 11 patients had an additional positive SLN that was called negative on frozen section. Intraoperative imprint cytology gained widespread interest in the early 2000s as a rapid alternative to frozen section that can sample a broader area of tissue with no concerns for tissue usage. After touch imprinting 1 to several lymph node surfaces to a glass slide, a variety of staining techniques that have been used, including Giemsa/Diff-Quik staining, hematoxylin-eosin (H&E) staining, and additional rapid immunohistochemical staining. A pooled analysis of 7784 breast carcinoma patients comparing IIC to permanent sections found a sensitivity of 33% to 73%
The Cancer Journal • Volume 21, Number 1, January/February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
www.journalppo.com
33
The Cancer Journal • Volume 21, Number 1, January/February 2015
Messina and Rosa
and specificity of 98% to 100%.6 The sensitivity in 1 large series was lower for lobular carcinoma (39%) than ductal carcinoma (56%), because of morphologic similarity with lymphocytes, and intraoperative immunohistochemistry (IHC) is particularly advocated for this histologic subset in groups performing IIC.11 In our practice, we recommend the use of IIC for all cases of breast SLN and do not perform frozen sections. While sensitivity for detection of micrometastasis is low, this limitation may not be crucial because ALND is not indicated in this subgroup. In melanoma, IIC has been shown to have a sensitivity of 33% to 61%, with a negligible false-positive rate. The sensitivity of IIC increases with the tumor stage, as high as 47% in patients with T4 lesions, and rises to 62% when metastases greater than 2 cm are present.12 Thus, it is acceptable to perform IIC in melanoma SLN and preferable to performing a frozen section, when metastasis is strongly suspected on gross examination.
Gross Dissection Techniques Standard gross dissection of all types of SLN begins with complete reporting of the anatomic location, SLN number, and, if indicated by surgeon, the presence or absence of blue dye, radioactivity counts, and hot spot. After proper fixation, any gross lesion, such as pigment or visible tumor, should be described and measured. Unless voluminous, the perinodal fat should not be dissected away, taking care not to disturb the lymph node capsule. If small (
