Cutting a sentinel lymph node into slices is the optimal first step for examination of sentinel lymph nodes in melanoma patients

Sentinel lymph node assessment in melanoma: current state and future directions

Assessment of sentinel lymph node status is an important step in the evaluation of patients with melanoma for both prognosis and therapeutic management. Pathologists have an important role in this evaluation. The methodologies have varied over time, from the evaluation of dimensions of metastatic burden to determination of the location of the tumour deposits within the lymph node to precise cell counting. However, no single method of sentinel lymph node tumour burden measurement can currently be used as a sole independent predictor of prognosis. The management approach to sentinel lymph node-positive patients has also evolved over time, with a more conservative approach recently recognised for selected cases. This review gives an overview of past and current status in the field with a glimpse into future directions based on prior experiences and clinical trials.

Longitudinal lymph node step-sectioning for the identification of metastatic disease in canine mast cell tumor

Lymph node (LN) metastasis in canine mast cell tumor (MCT) can affect prognosis and postsurgical treatment recommendations; however, routine histological single-section examination may underestimate the incidence of metastases. This prospective study aimed at determining whether longitudinal step-sectioning of the entire LN allows for a more reliable detection of metastases. Dogs with MCT undergoing resection of the primary tumor and regional lymphadenectomy were enrolled. Formalin-fixed LNs were bisected longitudinally, both halves were embedded in paraffin and histological sections prepared at 200 μm steps. The nodal mast cells were classified according to the Weishaar classification. First-section evaluation (FSE; ie, examination of the first section obtained from the blocks) and whole LN step-section evaluation (SSE) were compared. Fifty-eight LNs were included. The median number of sections per LN was 6 (range, 3–28). FSE with toluidine blue (TB) revealed 27 (47%) nonmetastatic (HN0), 14 (24%) premetastatic (HN1), 9 (15%) early metastatic (HN2), and 8 (14%) overtly metastatic (HN3) LNs. SSE with TB resulted in upgrading the LN status in 2 cases (HN2 to HN3; HN0 to HN1). Evaluation of the first section plus an additional step-section resulted in 100% accuracy. Compared with SSE with TB, the accuracy of FSE with HE was 98% for HN3 LNs and 74% for HN2 LNs. FSE appears to reliably allow for the detection of LN metastasis in MCT, although examination of a further parallel section at a 200 μm step may increase the accuracy. A metachromatic stain is recommended for the identification of early metastases.

High-resolution three-dimensional imaging for precise staging in melanoma

INTRODUCTION

Many cancer guidelines include sentinel lymph node (SLN) staging to identify microscopic metastatic disease. Current SLN analysis of melanoma patients is effective but has the substantial drawback that only a small representative portion of the node is sampled, whereas most of the tissue is discarded. This might explain the high clinical false-negative rate of current SLN diagnosis in melanoma. Furthermore, the quantitative assessment of metastatic load and microanatomical localisation might yield prognosis with higher precision. Thus, methods to analyse entire SLNs with cellular resolution apart from tedious sequential physical sectioning are required.

PATIENTS AND METHODS

Eleven melanoma patients eligible to undergo SLN biopsy were included in this prospective study. SLNs were fixed, optically cleared, whole-mount stained and imaged using light sheet fluorescence microscopy (LSFM). Subsequently, compatible and unbiased gold standard histopathological assessment allowed regular patient staging. This enabled intrasample comparison of LSFM and histological findings. In addition, the development of an algorithm, RAYhance, enabled easy-to-handle display of LSFM data in a browsable histologic slide-like fashion.

RESULTS

We comprehensively quantify total tumour volume while simultaneously visualising cellular and anatomical hallmarks of the associated SLN architecture. In a first-in-human study of 21 SLN of melanoma patients, LSFM not only confirmed all metastases identified by routine histopathological assessment but also additionally revealed metastases not detected by routine histology alone. This already led to additional therapeutic options for one patient.

CONCLUSION

Our three-dimensional digital pathology approach can increase sensitivity and accuracy of SLN metastasis detection and potentially alleviate the need for conventional histopathological assessment in the future. GERMAN CLINICAL TRIALS REGISTER: (DRKS00015737).

The sentinel node invasion level (SNIL) as a prognostic parameter in melanoma

Sentinel lymph node (SN) tumor burden is becoming increasingly important and is likely to be included in future N classifications in melanoma. Our aim was to investigate the prognostic significance of melanoma infiltration of various anatomically defined lymph node substructures. This retrospective cohort study included 1250 consecutive patients with SN biopsy. The pathology protocol required description of metastatic infiltration of each of the following lymph node substructures: intracapsular lymph vessels, subcapsular and transverse sinuses, cortex, paracortex, medulla, and capsule. Within the SN with the highest tumor burden, the SN invasion level (SNIL) was defined as follows: SNIL 1 = melanoma cells confined to intracapsular lymph vessels, subcapsular or transverse sinuses; SNIL 2 = melanoma infiltrating the cortex or paracortex; SNIL 3 = melanoma infiltrating the medulla or capsule. We classified 338 SN-positive patients according to the non-metric SNIL. Using Kaplan-Meier estimates and Cox models, recurrence-free survival (RFS), melanoma-specific survival (MSS) and nodal basin recurrence rates were analyzed. The median follow-up time was 75 months. The SNIL divided the SN-positive population into three groups with significantly different RFS, MSS, and nodal basin recurrence probabilities. The MSS of patients with SNIL 1 was virtually identical to that of SN-negative patients, whereas outgrowth of the metastasis from the parenchyma into the fibrous capsule or the medulla of the lymph node indicated a very poor prognosis. Thus, the SNIL may help to better assess the benefit-risk ratio of adjuvant therapies in patients with different SN metastasis patterns.

Pathology of sentinel lymph nodes: historical perspective and current applications in gynecologic cancer

Efforts to reduce surgical morbidity related to en bloc lymph node removal associated with cancer surgery led to the development of targeted lymph node sampling to identify the lymph node(s) most likely to harbor a metastasis. Through identification of one or only a few lymph nodes at highest risk, the overall number of lymph nodes removed could be markedly reduced. Submission of fewer lymph nodes affords more detailed pathologic examination than would otherwise be practical with a standard lymph node dissection. Such enhanced pathologic examination techniques (ie, ultra-staging) have contributed to increased detection of lymph node metastases, primarily by detection of low volume metastatic disease. Based on the success of sentinel lymph node mapping and ultra-staging in breast cancer and melanoma, such techniques are increasingly used for other organ systems including the gynecologic tract. This review addresses the historical aspects of sentinel lymph node evaluation and reviews current ultra-staging protocols as well as the implications associated with increased detection of low volume metastases.

Axillary sentinel node biopsy in prone position for melanomas on the upper back or nape

In patients with melanomas on the upper back or nape, axillary sentinel lymph node (SLN) biopsy (SLNB), when performed in the traditional supine position, is often disturbed by scattered radiation emitted from the primary tumor site. The results from the present study suggestthat axillary SLNB performed in the prone position can solve this problem. We compared two consecutive groups of patients with melanomas of the dorsal trunk or nape who received axillary SLNB performed either in the supine (n = 119) or in the prone position (n = 130). The number of SLNs detected and excised was significantly higher in prone position group (2.4 ± 1.5 SLNs versus 1.9 ± 0.95 SLNs, p = 0.002). Using the prone position, intra-operative repositioning of the patient for excision of a primary site of the upper back or neck was not necessary. The SLN identification rates and the SLN-positivity rates did not differ significantly between the two types of intraoperative patient positioning. There were no significant differences in survival outcomes or false-negative rates. In conclusion, axillary SLNB in prone position yields a higher number of excised SLNs in patients with melanomas of the upper back or nape. Axillary SLNB in prone position is easy to perform and reliable. Intraoperative repositioning of the patient is not necessary, which saves time and resources.

Exhaustive pathologic work-up in sentinel lymph node biopsy for melanoma: is it necessary?

The objective of this study is to determine whether a less exhaustive pathologic work-up to detect melanoma metastasis is clinically useful and does not affect patient prognosis. The success and evolution of the sentinel lymph node (SLN) depends on histological techniques. Several exhaustive protocols of SLN analysis have been published, but are time and cost consuming, with slight increases in the rates of metastasis detection. From 281 patients with SLN biopsy, each SLN was sectioned every 2 mm and from each paraffin block, 2-3 histological sections were evaluated. The patients were divided as follows: the first group (n=185) was subjected to extensive SLN examination (eSLNe) and the second group (n=96) was not subjected to an extensive SLN examination (wSLNe). The average SLN resected was 2 (range: 1-7), evaluating one in 50.9%. The SLN metastasis detection rate was 28.5%, whereas eSLNe increased by 3.2%. During follow-up, 4/26 (17.4%) cases in the wSLNe group showed recurrence in the SLN basin. Factors associated with decreased survival in univariant analysis were recurrence, Breslow thickness, advanced clinical stage, ulceration, and SLN metastasis. eSLNe did not affect disease-specific survival. Multivariate analysis showed recurrence (hazard ratio 23.475, 95% confidence interval: 1903-4559, P<0.001) and Breslow thickness of more than 3.5 mm (hazard ratio 15.222, 95% confidence interval: 1448-3059, P<0.001) as independent risk factors for decreased survival. Our routine for SLN examination enabled an adequate rate of SLN metastasis detection and the eSLNe increased the rate of detection in 3.2%, but did not affect the survival. We did not find any benefit from performing the eSLNe in patients with Breslow thickness less than 3.5 mm.

Nodal Basin Recurrence After Sentinel Lymph Node Biopsy for Melanoma: A Retrospective Multicenter Study in 2653 Patients

The objective of this study was to analyze different types of nodal basin recurrence after sentinel lymph node biopsy (SLNB) for melanoma.

PATIENTS AND METHODS

Kaplan-Meier estimates and the Cox proportional hazards model were used to study 2653 patients from 3 German melanoma centers retrospectively.The estimated 5-year negative predictive value of SLNB was 96.4%. The estimated false-negative (FN) rates after 1, 2, 3, 5, and 10 years were 2.5%, 4.6%, 6.4%, 8.7%, and 12.6%, respectively. Independent factors associated with false negativity were older age, fewer SLNs excised, and head or neck location of the primary tumor. Compared with SLN-positive patients, the FNs had a significantly lower survival. In SLN-positive patients undergoing completion lymphadenectomy (CLND), the 5-year nodal basin recurrence rate was 18.3%. The recurrence rates for axilla, groin, and neck were 17.2%, 15.5%, and 44.1%, respectively. Significant factors predicting local relapse after CLND were older age, head, or neck location of the primary tumor, ulceration, deeper penetration of the metastasis into the SLN, tumor-positive CLND, and >2 lymph node metastases. All kinds of nodal relapse were associated with a higher prevalence of in-transit metastases.The FN rate after SLNB steadily increases over the observation period and should, therefore, be estimated by the Kaplan-Meier method. False-negativity is associated with fewer SLNs excised. The beneficial effect of CLND on nodal basin disease control varies considerably across different risk groups. This should be kept in mind about SLN-positive patients when individual decisions on prophylactic CLND are taken.

Sentinel node biopsy improves prognostic stratification in patients with thin (pT1) melanomas and an additional risk factor

BACKGROUND

Sentinel lymph node (SLN) biopsy (SLNB) for pT1 melanomas is not generally recognized as a clinical standard. We studied the value of SLNB for pT1 melanoma patients having at least one additional risk factor.

PATIENTS

Among 931 patients with SLNB, 210 had pT1 melanomas. All of the latter showed at least one of the following risk factors: ulceration (4 %) Clark level IV (44 %), nodular growth pattern (11 %), mitoses (59 %), regression (38 %) or age ≤ 40 years (27 %).

RESULTS

In this selected pT1 population, we observed a surprisingly high SLN positivity rate of 18 %. The melanoma-specific overall survival significantly depended on SLN status. Compared with Clark IV, a lower invasion level (Clark II/III) was associated with a higher proportion of positive SLNs (25 vs. 10 %; p < 0.01). There was a trend towards a higher SLN positivity rate in younger patients (p = 0.06). Breslow, ulceration, mitoses, nodular growth pattern, and sex did not reach significance. Regression was significantly more frequently found in very thin melanomas (≤ 0.75 mm) and tended to be significant in this subgroup (p = 0.075).

CONCLUSIONS

SLNB improves prognostic stratification in patients with thin melanomas having an additional risk factor. Clark level IV most likely does not belong to these risk factors. The impact of regression deserves further consideration. Our data suggest that SLNB should be offered to patients with thin melanomas, if ulceration, nodular growth pattern, mitoses, or regression are present, or if the patient is younger than 40 years of age.

Lack of standards for the detection of melanoma in sentinel lymph nodes: a survey and recommendations

CONTEXT

Detection of microscopic melanoma metastases in sentinel lymph nodes drives clinical care; patients without metastases are observed, and patients with metastases are offered completion lymphadenectomy and adjuvant therapy.

OBJECTIVE

We sought to determine common elements in currently used analytic platforms for sentinel lymph nodes in melanoma patients.

DESIGN

An electronic survey was distributed to 83 cancer centers in North America.

RESULTS

Seventeen responses (20%) were received. The number of sentinel lymph node mapping procedures for melanoma ranged from less than 11 to more than 100 patients per year, with 72% of institutions mapping more than 50 melanoma patients a year. Uniform practices included (1) processing all of the lymph node tissue rather than submitting representative sections and (2) use of immunohistochemical stains if no tumor was identified on the hematoxylin-eosin-stained sections. Significant variability existed regarding the method of sectioning lymph nodes at grossing and in the histology laboratory; most bisected nodes longitudinally (94%) and performed deeper levels into the block (67%), but these were not uniform practices. S-100 was the most commonly used immunohistochemical stain (78%), followed by Melan-A (56%), MART-1 (50%), HMB-45 (44%), tyrosinase (33%), MiTF (11%), and pan-melanoma (6%).

CONCLUSIONS

There is a need for a standardized platform for detecting melanoma in sentinel lymph nodes. Current practices by a majority of laboratories and findings in the reported literature support the following: histologic evaluation of all lymph node tissue, use of immunohistochemical stains, bisecting lymph nodes longitudinally, and performing deeper levels into the tissue block.

Individualized surgery: gamma-probe-guided lymphadenectomy in patients with clinically enlarged lymph node metastases from melanomas

Background

The value of a preoperative lymphoscintigraphy in melanoma patients with clinically evident regional lymph node metastases has not been studied. Therapeutic lymph node dissection (TLND) is regarded as the clinical standard, but the appropriate extent of TLND is controversial in all lymphatic basins.

Patients and Methods

Of the 115 consecutive patients with surgery on palpable lymph node metastases, 34 received a pre-operative lymphoscintigraphy. Lymphatic drainage to a second nodal basin outside the clinically involved basin was found in 15 cases. In 13 patients, the ectopic tumor-draining lymph nodes were excised as in a sentinel node biopsy. The lymph nodes from the TLND specimens were postoperatively separated and classified as either radioactive or non-radioactive.

Results

A total of 493 lymph nodes were examined pathologically. The largest macrometastasis maintained the ability to take up radiotracer in 77% of cases. Radioactively labeled lymph nodes carried a higher risk of being involved with metastasis. The proportions of tumor involvement for radioactive and non-radioactive lymph nodes were 44.5 and 16.9%, respectively (P=0.00002). Of the 13 ectopic nodal basins surgically explored, six harbored clinically occult metastases.

Conclusion

In patients undergoing TLND for palpable metastases, tumor-draining lymph nodes in a second, ectopic nodal basin should be excised, because they could be affected by occult metastasis. With respect to radioactive lymph nodes situated within the nodal basin of the macrometastasis but beyond the borders of a less-radical lymphadenectomy, further studies are needed.

A mathematical approach to the optimal examination of lymph nodes

There is no scientific evidence to support the idea that serial sectioning along the short axis of the lymph node is superior to a single bisection along the long axis. We mathematically evaluated methods of lymph node dissection and applied the result to six lymph nodes that had produced false negative results at the time of frozen examination. We simplified the geometry of a lymph node to that of a three-dimensional ellipse and compared two different cutting methods. Let A be the cross-sectional area obtained through a single bisection along the long axis, and let B be the sum of the cross-sectional areas of n fragments obtained via serial cutting along the short axis. The smallest n (n*) that makes a B larger than A can be calculated. n* = [3L + √9L² + 16S²)/4S]. ([α], the smallest integer greater than or equal to α; L, long axis; S, short axis). The probabilities of tumor detection when the node is bisected along the long axis (P(D(A)|E)) and when serially cut along the short axis (P(D(B)|E)) are as follows. P(D(A)|E = {(3/2)S² - 3ST + T²}T/(S - T)³. and P(D(B)|E) = (n - 1){(1 + 1/n)L² - 3LT + T²}T/(L - T)³. (T, size of the tumor cell cluster). According to these formulas, three out of six lymph nodes were not examined in the most appropriate manner.

The popliteal fossa - a problem zone for sentinel lymphonodectomy

BACKGROUND

The impact of lymphatic drainage to popliteal sentinel lymph nodes (SLNs) has yet to be explored in detail.

PATIENTS AND METHODS

We performed lymphoscintigraphy on 663 patients with cutaneous melanomas. The following day sentinel lymphonodectomy was performed. SLNs were studied on serial sections with both histology and immunohistochemistry.

RESULTS

166 patients had a melanoma located on the foot, the lower leg or the knee, i. e., the potential of lymphatic drainage to the popliteal lymph nodes. On lymphoscintigraphy, only 16 patients (9.6 %) showed popliteal SLNs. A popliteal SLN was surgically identified in only 6 of the 16 patients. The reason for the poor identification rate was exhausted radioactivity in the small popliteal nodes the day after lymphoscintigraphy. In 3 cases, popliteal SLN metastasis was diagnosed. All but one patient had an additional drainage to the inguinal lymph nodes; inguinal SLN metastasis was diagnosed in 7 patients. Even all 16 patients showed lymphatic drainage to iliac lymph nodes, metastasis in the pelvis was diagnosed in 4 patients.

CONCLUSIONS

Popliteal SLNs are observed in less than 10 % of the patients with melanomas of the distal leg. In the case of suspected popliteal drainage, lymphoscintigraphy should be performed on the day of sentinel lymphonodectomy because the radioactivity of the small and deeply situated popliteal nodes diminishes rapidly. With respect to complete lymphadenectomy, decision-making is difficult since three nodal basins (popliteal, inguinal and iliac) may harbor metastases.