Sentinel lymph node (SN) biopsy plays a significant role in breast cancer staging and treatment. While this procedure is generally accurate, false-negative results have been reported. The authors describe one such case involving a young patient with an infiltrating ductal carcinoma of the left breast. The patient underwent mastectomy and SN biopsy, which indicated the SN was negative for metastatic disease, but two lymph nodes within the specimen demonstrated evidence of metastasis. The authors discuss the etiologies and clinical implications of false-negative biopsies and provide a review of the literature.

Sentinel lymph node (SN) biopsy has been shown to be an acceptable alternative to axillary dissection in delineating axillary nodal status. Since SN biopsy has come into the forefront of breast cancer surgery, many studies have been undertaken to assess its accuracy. One problem associated with this technique is the false-negative rate, which numerous studies have shown to be between 5% and 10%.¹ Because axillary lymph node status is an important factor in determining management and prognosis, concerns have been raised over the clinical implications of a false-negative SN biopsy.

Case report

A 23-year-old woman presented with a 1½-month history of a left upper outer quadrant breast mass, which was discovered on self-examination. The mass had increased in size, but there was no tenderness, nipple discharge, or history of trauma. She did not have any previous breast abnormalities. The patient was 13 years old when she had her first menses and was gravida 0. She was in otherwise good health, and her only current medication was an oral contraceptive.

The patient's family history was significant for breast cancer diagnosed in two paternal relatives at a young age: her grandmother while in her 30s and an aunt at age 20. Additionally, lung cancer was diagnosed in three maternal family members: her mother at age 53, an aunt, and her grandmother. Adrenal carcinoma was also diagnosed in her brother when he was 13.

On physical examination, the patient's breasts were noted to be symmetrical and small. A 2-cm, irregular, firm, solid mass was easily palpable in the 1 o'clock position of the upper outer quadrant of the left breast. There was no axillary lymphadenopathy, overlying skin changes, or other abnormal findings.

Figure 1—Ultrasonography showing a 2-cm left breast mass with mixed echogenicity (crosshairs).

Ultrasonography revealed a 2-cm, poorly marginated mass with mixed echogenicity (Figure 1). A core needle biopsy revealed a grade III infiltrating ductal carcinoma. After extensive discussion, the patient elected to proceed with a mastectomy (due to the small size of her breast) and an SN biopsy using isosulfan blue and lymphoscintigraphy.

The breast was massaged for 5 minutes before injection of 5 cc of 1% isosulfan blue dye into the dermal plane in the subareolar position. Two SNs were excised, and touch prep analysis determined that they were negative for metastatic disease. Pathologic evaluation showed a 3.3 x 2.2 x 1.7-cm, grade III, infiltrating carcinoma with ductal and lobular features and high-grade ductal carcinoma in situ (Figure 2). Multiple foci of lymphatic space invasion were identified at the borders of the tumor. The SNs were negative for metastatic carcinoma; however, two of four intramammary lymph nodes showed metastatic disease. One lymph node was replaced by tumor (3-mm in diameter), and one showed micrometastasis, between 0.2 and 2 mm in size (Figure 3). The immunohistochemical studies showed nuclear immunoreactivity for estrogen and progesterone receptors. Although immunohistochemical studies showed overexpression of HER-2/neu oncoprotein (CB11 antibody, 2+), fluorescence in situ hybridization showed no evidence of HER-2/neu gene amplification.

One week after the mastectomy, a completion axillary dissection was performed and revealed no additional lymph node metastases. The patient's cancer was classified as stage II (pT2 pN1a M0), without clinical evidence of distant metastases. She underwent chemotherapy with doxorubicin and cyclophosphamide for 4 cycles and paclitaxel for 12 cycles, followed by regional radiation. She is pursuing genetic testing and has proceeded with a prophylactic right mastectomy with reconstruction.

Figure 2—Histopathology of the infiltrating tumor showing ductal and lobular features and lymphatic space invasion. A mixture of cribriform and solid ductal carcinoma in situ is also present (hematoxylin and eosin staining, magnification x100).

A

B
Figure 3—Histopathology images using hematoxylin and eosin staining showing micrometastasis in the lymph node capsule (A) and isolated tumor cells in the subcapsular sinus (B).

Discussion

Since SN biopsy has come into the forefront of modern-day breast surgery, many definitions have been cultivated as to what constitutes an SN. The classic definition is that this node is the first lymph node into which the primary tumor drains.² Other definitions have included the following: (1) the node closest to the lesion; (2) the hottest node on lymphoscintigraphy; (3) the first node depicted on lymphoscintigraphy; or (4) a blue node. More recently, the classification of these nodes has been adapted such that an SN is any lymph node on the direct drainage pathway from the primary tumor.³ According to this classification, the nodal basin draining from the primary tumor area must be identified.

To identify the nodal basin, an understanding of the drainage patterns of the breast is required. Estourgie and colleagues found that 97.7% of palpable upper outer quadrant lesions drained into the axilla, whereas nonpalpable upper outer quadrant lesions only had an 89.2% drainage pattern to the axilla, with 23% draining into the internal mammary chain.⁴ Based on these findings, the authors con-cluded that there was a distinct difference in drainage configurations between palpable and nonpalpable breast lesions. Nonpalpable breast lesions had a greater tendency to drain into the internal mammary chain, regardless of the primary tumor's quadrant of origin. In addition, the lateral side of the breast was noted to drain into the internal mammary chain as well as the axilla in 10% to 30% of patients.⁴ Extra-axillary SNs, excluding internal mammary chains, were positive for tumor in 16% of patients.⁴ These findings indicate that lymphatic drainage to an extra-axillary SN occurs in a considerable number of patients.

In our patient, one intraparenchymal lymph node adjacent to the tumor demonstrated micrometastasis. Egan and associates' study of 158 mastectomy specimens revealed intramammary nodes in 28% of cases, with 10% of those containing metastatic deposits.⁵ The positive lymph nodes were found in the same quadrant as the primary tumor only 50% of the time. In terms of stage II disease, a positive intramammary node suggests advanced disease and indicates a greater likelihood of axillary metastatic disease.

The methods for identifying SNs and their drainage pathways have been described extensively in the literature. The most common methods include use of vital blue dye, lymphoscintigraphy with intraoperative use of a gamma probe, or both of these.⁶ Common injection approaches during SN biopsy are peritumoral, dermal, periareolar, subareolar, and intratumoral, with many practitioners using a combination of these techniques. All of these methods have acceptable SN retrieval rates; however, SN identification rates have been shown to be slightly higher with superficial techniques (dermal, subareolar, and periareolar). Superficial methods have been associated with drainage confined to the axillary basin, whereas deeper injections are associated with a 22% incidence of localizing to nodal basins outside of the axilla.⁷ In addition, 16% to 21% of these extra-axillary SNs will be found to have metastatic disease upon removal.⁷

Peritumoral injection has been associated with limitations in patients with upper outer quadrant lesions. Krag and colleagues described peritumoral injection of technetium Tc 99m sulfur colloid and noted that all false-negative SNs in their series were found in patients with upper outer quadrant lesions.⁸ Because the site of injection is close to the axilla in these cases, high background activity may make it difficult for the surgeon to localize the SN with the gamma probe. Krag and colleagues' theory with regard to the false-negative status of these patients was that lymphatics tend to converge in the area of the axilla; thus, widely spaced injections around a tumor could miss the important draining lymphatic channel.⁸

Subareolar and subdermal injections have produced excellent results in identifying the SN and within a shorter interval than peritumoral injections. One study reported a 99% and 96% SN identification rate after radioactive colloid injection using subareolar and periareolar techniques, respectively.⁹ Both techniques were associated with false-negative rates of approximately 8%, which was comparable with peritumoral, dermal, or subdermal techniques.⁹ However, the subareolar technique is associated with a much lower SN identification rate in the internal mammary chain.¹⁰ In addition, previous breast surgeries have been associated with failure of localization of the SN when the subareolar technique is used. Layeeque and colleagues noted failure of SN localization in 3% of patients: one patient had a previous circumareolar excisional biopsy, and two patients had upper outer quadrant incisions.⁹

Early lymphoscintigraphy images can visualize the lymphatic channels and thereby delineate the order of drainage. Many investigators define the SN as the first node that becomes visible on these images; however, since multiple lymphatic channels can originate from the same region, several nodes may light up.³ These nodes are often visualized at different times on this imaging modality, with some nodes lighting up in later images. Some investigators have suggested that, in these instances, the SN is the first node that lights up on lymphoscintigraphy, but just because other nodes are depicted later on does not necessarily make them second-tier nodes.³ All lymph nodes that have demonstrated a direct drainage pathway from the site of the primary tumor should be removed and sent for pathologic examination.

Identifying the SN as the hottest node can also be misleading. Although it is most often the first node to be invaded by tumor cells, there are exceptions. Martin and associates focused on the isotope count and its ability to predict SN positivity in patients.¹¹ They found that the node with the highest count contained tumor in 80% of SN-positive cases, while 20% of positive cases were notable for the hottest node containing no tumor. Among this 20%, the counts of the hottest node surpassed the histopathologic positive nodes by a ratio of at least 10:1 in 31% of the cases. This suggests that SNs may receive a small amount of lymphatic supply due to obstruction of lymph flow by metastatic disease.¹² It is possible that a node can be laden with such a large tumor burden that it does not take up the tracer.³ Nodes that contain a large tumor burden may be identified on ultrasonography or may be large enough to be palpated in the biopsy wound cavity.¹³

The status of the SN has been used to predict the status of the remaining nodes in the basin.⁶ Multiple studies have been performed to assess the accuracy of the SN in staging the axilla. These studies have demonstrated a 5% to 10% false-negative rate associated with SN biopsy.¹ Use of a gamma probe increases the overall detection rate, identifying SNs in 84% of patients versus a 67% detection rate in those patients who receive blue dye alone.⁶ Because the probe cannot visualize lymphatic channels, it has some limitations, and secondary nodes may be removed unnecessarily. In addition, 15% to 30% of SNs are only blue and not radioactive.¹³

Nano and associates identified the SN in 86.9% of 328 women using lympho-scintigraphy, blue dye, or both.¹ All patients in the study underwent immediate axillary dissection after the SN had been identified. A false-negative rate of 7.9% was noted, although in three cases, palpable nodal deposits were clinically evident upon entrance to the axilla. In this study, only 2 of 285 women (0.7%) received no adjuvant systemic therapy based on clinical and histological features of the primary tumor, which appeared to indicate negative axillary status. As such, the projected survival for those two women may have been affected by the false-negative SN biopsy.¹

Because false-negative SN biopsies occur, one must clearly define what constitutes a false-negative SN. Nano and colleagues defined a false-negative result as a negative SN in the presence of other axillary non-SNs that contain metastatic tumor deposits.¹ Nieweg and Estourgie went one step further and proposed three definitions of a false-negative result, each definition taking into consideration the goal of the procedure performed.³ The first definition recognizes that the singular goal of SN biopsy is to identify the SN; thus, the procedure would be false-negative if the SN was benign but tumor was identified in any axillary node. The second definition entails removal of apparently abnormal non-SN (via palpation or visualization) along with the SN, and the procedure would be false-negative if unintentionally removed nodes within the specimen tested positive for tumor. The third definition denotes axillary recurrence developing during follow-up as a false-negative finding. In this instance, the sole purpose of the SN biopsy is to detect metastases in the axilla.

Multiple studies addressing the accuracy of SN biopsy as a less-invasive modality in breast cancer staging have lead to criteria regarding indications and contraindications for this procedure. It is well accepted that SN biopsy is indicated in T1 and T2 lesions without palpable axillary lymph nodes. There has been ongoing controversy, however, regarding SN biopsy for staging of large breast tumors. A study by Bedrosian and colleagues included 103 patients with primary breast tumors larger than 2 cm and demonstrated an overall accuracy of 99% in identifying the SN.¹⁴ In this study, there was an SN false-negative rate of 3% in patients with T2 or larger tumors. One patient with a 2.1-cm primary tumor and negative SN by immunochemistry and serial sectioning had a micrometastasis in a non-SN. Another patient with a false-negative SN and a 5-cm tumor had a 5-mm metastasis to a non-SN. Neither patient had undergone previous excisional breast biopsy. Not surprisingly, Bedrosian and colleagues' series demonstrated an increasing incidence of lymph node involvement correlating with increasing tumor size.¹⁴ Primary breast tumors measuring 2.1 cm to 2.9 cm were associated with a 54% incidence of axillary lymph node involvement, and tumors 3 cm or larger were associated with a 62.5% incidence. Tumors larger than 5 cm were associated with an 80% incidence of nodal metastasis. Because of the high rate of nodal metastasis observed in T3 lesions, SN biopsy for these lesions is controversial; however, it is absolutely contraindicated in T4 lesions.

Palpable axillary nodes, multifocal breast cancer, and previous radiotherapy or major surgery to the breast or axilla have been cited as contraindications. It has long been thought that radiotherapy and surgery to the breast or axilla affect the architectural pattern of lymphatic flow in the breast, thereby leading to an increased rate of false-negative SN biopsies. The role of SN biopsy in patients who have undergone previous axillary surgery is being reevaluated.¹⁵ Studies evaluating patients with previous excisional biopsies have demonstrated a high negative predictive value and high success rate with SN localization.^10,15 A study of 2,206 patients found no difference in SN identification rate or SN false-negative rate between patients who underwent needle biopsy or those who had excisional biopsy.¹⁶

Conclusion

SNs can be false-negative for a variety of reasons. There may be an array of lymphatic drainage pathways originating from the region of the primary tumor. Some of these primary pathways may branch out to multiple lymph nodes. Some of the pathways may be obstructed secondary to tumor burden, thereby diverting the expected course of lymphatic flow and, in some cases, replacing normal nodal tisue. Disruption of lymphatic drainage may alter the course of lymphatic flow in patients who have undergone previous surgery or biopsy, which could lead to decreased uptake of tracer or blue dye and give false results. While the false-negative rate of SN biopsy has been demonstrated to be acceptably low, the clinical impact of SN biopsy on survival remains to be seen.

References

1. Nano MT, Kollias J, Farshid G, et al. Clinical impact of false-negative sentinel node biopsy in primary breast cancer. Br J Surg. 2002;89(11):1430-1434.
2. Morton DL, Wen DR, Wong JH, et al. Technical details of intraoperative lymphatic mapping for early stage melanoma. Arch Surg. 1992;127(4):392-399.
3. Nieweg OE, Estourgie SH. What is a sentinel node and what is a false-negative sentinel node? Ann Surg Oncol. 2004;11 (3 Suppl):S169-S173.
4. Estourgie SH, Nieweg OE, Olmos RA, et al. Lymphatic drainage patterns from the breast. Ann Surg. 2004;239(2):232-237.
5. Egan RL, McSweeney MB. Intramammary lymph nodes. Cancer. 1983;51(10):1838-1842.
6. Bergkvist L, Frisell J, Liljegren G, et al. Multicentre study of detection and false-negative rates in sentinel node biopsy for breast cancer. Br J Surg. 2001;88(12):1644-1648.
7. Harlow S, Krag D, Reintgen D, et al. Lymphatic mapping and sentinel lymph node biopsy. In: ACS Surgery: Principles and Practice. New York, NY: WebMD; 2006:chap 6.
8. Krag D, Weaver D, Ashikaga T, et al. The sentinel node in breast cancer-a multicenter validation study. N Engl J Med. 1998;339(14):941-946.
9. Layeeque R, Kepple J, Henry-Tillman RS, et al. Intraoperative subareolar radioisotope injection for immediate sentinel lymph node biopsy. Ann Surg. 2004;239(6):841-848.
10. Youssef I, Abdel-Dayem H. Breast cancer and the role of sentinel lymph node localization. J Womens Imaging. 2004;6(3): 114-124.
11. Martin RC, Fey J, Yeung H, et al. Highest isotope count does not predict sentinel node positivity in all breast cancer patients. Ann Surg Oncol. 2001;8(7):592-597.
12. Borgstein PJ, Pijpers R, Comans EF, et al. Sentinel lymph node biopsy in breast cancer: guidelines and pitfalls of lymphoscintigraphy and gamma probe detection. J Am Coll Surg. 1998;186(3):275-283.
13. Estourgie SH, Nieweg OE, Valdes Olmos RA, et al. Eight false negative sentinel node procedures in breast cancer: what went wrong? Eur J Surg Oncol. 2003;29(4):336-340.
14. Bedrosian I, Reynolds C, Mick R, et al. Accuracy of sentinel lymph node biopsy in patients with large primary breast tumors. Cancer. 2000;88(11):2540-2545.
15. Bland K, Copeland E. Lymphatic mapping and sentinel lymphadenectomy for breast cancer. In: The Breast: Comprehensive Management of Benign and Malignant Disorders. St. Louis, Mo: Saunders; 2004:chap 51.
16. Wong SL, Edwards MJ, Chao C, et al. University of Louisville Breast Cancer Study Group. The effect of prior breast biopsy method and concurrent definitive breast procedure on success and accuracy of sentinel lymph node biopsy. Ann Surg Oncol. 2002;9(3):272-277.