The Distribution of Microscopic Melanoma Metastases in Sentinel Lymph Nodes: Implications for Pathology Protocols

Contrast-enhanced and indirect computed tomography lymphangiography accurately identifies the cervical lymphocenter at risk for metastasis in pet dogs with spontaneously occurring oral neoplasia

For dogs with oral tumors, cervical lymph node (LN) metastasis alters treatment and prognosis. It is therefore prudent to make an accurate determination of the clinical presence (cN+ neck) or absence (cN0 neck) of metastasis prior to treatment. Currently, surgical LN extirpation with histopathology is the gold standard for a diagnosis of metastasis. Yet, recommendations to perform elective neck dissection (END) for staging are rare due to morbidity. Sentinel lymph node (SLN) mapping with indirect computed tomography lymphangiography (ICTL) followed by targeted biopsy (SLNB) is an alternative option to END. In this prospective study, SLN mapping followed by bilateral END of all mandibular LNs (MLNs) and medial retropharyngeal LNs (MRLNs) was performed in 39 dogs with spontaneously occurring oral neoplasia. A SLN was identified by ICTL in 38 (97%) dogs. Lymphatic drainage patterns were variable although most often the SLN was identified as a single ipsilateral MLN. In the 13 dogs (33%) with histopathologically confirmed LN metastasis, ICTL correctly identified the draining lymphocentrum in all (100%). Metastasis was confined to the SLN in 11 dogs (85%); 2 dogs (15%) had metastasis beyond the SLN ipsilaterally. Contrast enhanced CT features had good accuracy in predicting metastasis, with short axis measurements less than 10.5 mm most predictive. ICTL imaging features alone were unable to predict metastasis. Cytologic or histopathologic SLN sampling is recommended prior to treatment to inform clinical decision-making. This is the largest study to show potential clinical utility of minimally invasive ICTL for cervical LN evaluation in canine oral tumors.

Melanoma lymph node metastases - moving beyond quantity in clinical trial design and contemporary practice

The presence of lymph node metastases is a well-studied prognostic factor for cutaneous melanoma. Characterization of melanoma lymph node metastases and their association with survival in multiple, large observational studies has led to recognition of the following high-risk features: quantity of lymph node metastases (number of nodes), size of the nodal tumor deposit (in mm), and extracapsular extension. Despite increasing utilization of these features in the design of randomized clinical trials, in addition to their role in contemporary clinical decision-making, current staging systems lag behind, only accounting for the quantity of lymph nodes with metastases. Herein, we review the prognostic role of melanoma lymph node metastases and their high-risk features, current reporting standards, how such features have been utilized in practice-changing trials, and best practices for future clinical trial design and clinical decision-making.

Oncogenic Alterations in Histologically Negative Lymph Nodes Are Associated with Prognosis of Patients with Stage I Lung Adenocarcinoma

Simple Summary

Lymph nodes (LNs) metastasis is one of the most important factors affecting the outcome of non-small cell lung. The aim of this study is to explore whether presence of oncogenic alterations in histologically-negative lymph nodes (LNs) can be of prognostic significance in stage I lung adenocarcinoma (LUAD). We confirmed that presence of oncogenic alterations in regional LN may be associated with higher risks of postsurgical recurrence of Stage I LUAD, particularly for certain molecular subgroups. These results warranted future studies on larger cohort of NSCLC patients using more comprehensive cancer gene panels to establish the clinical impact of molecular LN occult metastasis for localized NSCLC and identify Stage I patients at high risks for recurrence for appropriate adjuvant therapy.

Abstract

Background: Survival of patients with stage I non-small cell lung cancer (NSCLC) varies greatly. We sought to explore whether presence of oncogenic alterations in histologically-negative lymph nodes (LNs) can be of prognostic significance in stage I lung adenocarcinoma (LUAD). Methods: Genomic analysis of oncogenic alterations was applied to 123 stage I LUAD tumors. The same genomic variants identified in primary tumors were examined in corresponding histologically-negative LNs. Results: A total of 102 (82.9%) patients had at least one canonical oncogenic alteration detected in primary tumors, and 57 LNs from 12 patients (11.8%) were found to carry the identical oncogenic alterations detected in the corresponding primary tumor tissues, including EGFR mutations (six cases), KRAS mutations (three cases), ALK fusion (one case), BRAF mutation (one case) and HER2 & NRAS co-mutations (one case). None of these LNs was found to have occult tumor cells by routine pathological assessment or immunohistochemistry staining using antibodies against pan-cytokeratins (AE1/AE3) and the epithelial marker Ber-EP4. The detection rate of oncogenenic alterations in LN was significantly higher in RAS-mutant tumors than EGFR mutant tumors (36.36% verse 7.41%, p = 0.017). Patients with oncogenic alterations in LN showed inferior disease-free survival (DFS, p = 0.025) and overall survival (OS, p = 0.027). Furthermore, patients with RAS-mutations detected in LN had the worst DFS and OS (p = 0.001). Among the 11 patients with RAS mutation in primary tumors, DFS and OS in the four patients with mutations detected in LN were significantly shorter than the remaining seven patients without mutations LN (DFS, p = 0.001, OS, p = 0.002). Conclusions: Genomic analysis has the potential to detect oncogenic alterations in regional LNs for localized LUAD and presence of oncogenic alterations in regional LN may be associated with inferior clinical outcome of stage I LUAD, particularly for certain molecular subgroups. ClinicalTrials.gov ID NCT04266691

Nodal Recurrence is a Primary Driver of Early Relapse for Patients with Sentinel Lymph Node-Positive Melanoma in the Modern Therapeutic Era

BACKGROUND

Management of patients with sentinel lymph node (SLN)-positive melanoma has changed dramatically over the last few years such that completion lymph node dissection (CLND) has become uncommon, and many patients receive adjuvant immunotherapy or targeted therapy. This study seeks to characterize patterns and predictors of early recurrence in this setting.

PATIENTS AND METHODS

All patients with primary cutaneous melanoma undergoing sentinel lymph node biopsy (SLNB) between 3/2016 and 12/2019 were identified. The subset with a positive SLN who did not undergo CLND were examined for further analysis of outcomes and predictors of recurrence.

RESULTS

Overall, 215 patients with SLN-positive melanoma who did not have CLND were identified. Adjuvant systemic therapy was administered to 102 (47%), with 93% of this subset receiving immunotherapy (n = 95). Median follow-up from SLNB was 20 months (IQR 12-28.5 months), and 57 patients (27%) recurred during this time. The SLN basin was the most common site of recurrence (n = 38, 67% of recurrence), with isolated nodal recurrence being the most common first site of recurrent disease (n = 22, 39% of recurrence). On multivariable analysis, lymphovascular invasion (LVI) of the primary tumor, two or more involved nodes, and > 1 mm nodal deposit were independently associated with higher rates of nodal relapse.

CONCLUSIONS

Nodal recurrence is a primary driver of early disease relapse for patients with SLN-positive melanoma who do not undergo CLND in the era of effective adjuvant systemic therapy. LVI, ≥ 2 nodes, or > 1 mm nodal disease identifies patients at particularly high risk of nodal relapse.

Flow Cytometry for Detection and Quantification of Micrometastases in Sentinel Lymph Nodes from Patients with Primary Melanoma

BACKGROUND

Detection of micrometastases in the regional lymph nodes is one of the most important prognostic factors for melanoma patients. Our aim was to evaluate the suitability of flow cytometry for rapid quantification of disseminated melanoma cells in sentinel lymph nodes (SLN).

METHODS

132 SLNs from 104 patients diagnosed with melanoma were analyzed by flow cytometry, utilizing the extracellular marker melanoma-associated chondroitin sulfate proteoglycan, in addition to quantitative immunocytology and conventional histopathology, including immunohistochemistry. For quantification, the number of melanoma-positive cells per million lymph node cells (disseminated cancer cell density, DCCD) detected by flow cytometry was compared to the DCCD obtained by immunocytology.

RESULTS

Compared to histopathology and immunocytology, flow cytometry exhibited a sensitivity of 50% and a specificity of 85%. DCCDs of immunocytology and flow cytometry of the 37 immunocytologically positive SLNs showed a positive correlation (Spearman's ρ = 0.7, P < 0.0001). In 10 SLNs from 9 patients with high tumor load, the flow cytometric DCCD was 8-fold higher on average than the immunocytologic DCCD.

CONCLUSIONS

Although flow cytometry is not yet suitable for early detection of metastatic melanoma, it promises to become a valuable tool for rapidly quantifying tumor load in high-risk patients.

Model Combining Tumor Molecular and Clinicopathologic Risk Factors Predicts Sentinel Lymph Node Metastasis in Primary Cutaneous Melanoma

Purpose

More than 80% of patients who undergo sentinel lymph node (SLN) biopsy have no nodal metastasis. Here we describe a model that combines clinicopathologic and molecular variables to identify patients with thin and intermediate thickness melanomas who may forgo the SLN biopsy procedure due to their low risk of nodal metastasis.

Patients and Methods

Genes with functional roles in melanoma metastasis were discovered by analysis of next generation sequencing data and case control studies. We then used PCR to quantify gene expression in diagnostic biopsy tissue across a prospectively designed archival cohort of 754 consecutive thin and intermediate thickness primary cutaneous melanomas. Outcome of interest was SLN biopsy metastasis within 90 days of melanoma diagnosis. A penalized maximum likelihood estimation algorithm was used to train logistic regression models in a repeated cross validation scheme to predict the presence of SLN metastasis from molecular, clinical and histologic variables.

Results

Expression of genes with roles in epithelial-to-mesenchymal transition (glia derived nexin, growth differentiation factor 15, integrin β3, interleukin 8, lysyl oxidase homolog 4, TGFβ receptor type 1 and tissue-type plasminogen activator) and melanosome function (melanoma antigen recognized by T cells 1) were associated with SLN metastasis. The predictive ability of a model that only considered clinicopathologic or gene expression variables was outperformed by a model which included molecular variables in combination with the clinicopathologic predictors Breslow thickness and patient age; AUC, 0.82; 95% CI, 0.78-0.86; SLN biopsy reduction rate of 42% at a negative predictive value of 96%.

Conclusion

A combined model including clinicopathologic and gene expression variables improved the identification of melanoma patients who may forgo the SLN biopsy procedure due to their low risk of nodal metastasis.

Utility of Multistep Protocols in the Analysis of Sentinel Lymph Nodes in Cutaneous Melanoma: An Assessment of 194 Cases

Context.—

Currently, no universal protocol exists for the assessment of sentinel lymph nodes (SLNs) in cutaneous melanoma. Many institutions use a multistep approach with multiple hematoxylin-eosin (H&E) and immunohistochemical stains. However, this can be a costly and time- and resource-consuming task.

Objective.—

To assess the utility for multistep protocols in the analysis of melanoma SLNs by specifically evaluating the Calgary Laboratory Services (CLS) protocol (which consists of 3 H&E slides and 1 S100 protein, 1 HMB-45, and 1 Melan-A slide per melanoma SLN block) and to develop a more streamlined protocol.

Design.—

Histologic slides from SLN resections from 194 patients with diagnosed cutaneous melanoma were submitted to the CLS dermatopathology group. Tissue blocks were processed according to the CLS SLN protocol. The slides were re-reviewed to determine whether or not metastatic melanoma was identified microscopically at each step of the protocol. Using SPSS software, a decision tree was then created to determine which step most accurately reflected the true diagnosis.

Results.—

We found with Melan-A immunostain that 337 of 337 negative SLNs (100%) were correctly diagnosed as negative and 55 of 56 positive nodes (98.2%) were correctly diagnosed as positive. With the addition of an H&E level, 393 of 393 SLNs (100%) were accurately diagnosed.

Conclusions.—

We recommend routine melanoma SLN evaluation protocols be limited to 2 slides: 1 H&E stain and 1 Melan-A stain. This protocol is both time- and cost-efficient and yields high diagnostic accuracy.

Probabilistic issues with sentinel lymph nodes in malignant melanoma

OBJECTIVES

To address issues of probability for sentinel lymph node results in melanoma and provide details about the probabilistic nature of the numbers of sentinel nodes as well as to address how these issues relate to tumor thickness and patient outcomes.

METHODS

Analysis of the probability of observing sentinel node metastases uses the discrete exponential probability distribution to address the number of observed positive sentinel nodes. In addition, mathematical functions derived from survival analysis are used. Data are then chosen from the literature to illustrate the approach and to derive results.

RESULTS

Observations about the numbers of positive and negative sentinel nodes closely follow discrete exponential probability distributions, and the relationship between the probability of a positive sentinel node and tumor thickness follows closely a function derived from survival analysis. Sentinel node results relate to tumor thickness as well as to the total number of nodes harvested but fall short of identifying all those who eventually develop metastatic melanoma.

CONCLUSIONS

Probability analyses provide useful insight into the success and failure of the sentinel node biopsy procedure in patients with melanoma.

Histopathologic evaluation of the sentinel lymph node for malignant melanoma: the unstandardized process

Metastasis from malignant melanoma (MM) usually first presents in the draining lymph node basin and thus sentinel lymph node (SLN) biopsy is a staging tool used to predict risk of metastases and death in higher risk tumors and has become the standard of care. Differences in the processing and methods used in the histopathological examination of SLNs can affect the positivity rate for metastatic MM because isolated MM deposits may be small and variably distributed in the SLN. The examination of SLNs is not standardized. The authors surveyed institutions across the United States who process SLNs for MM to better characterize the current methods used and to suggest a standardized approach to improve the reliability of the SLN biopsy. A survey of 142 academic institutions in the United States regarding the methods used in the evaluation of the SLN biopsy for MM was conducted. Thirty-two institutions responded. Eighty-one percent of the institutions (26 of 32) had a protocol that they used for SLN examination. In regards to gross dissection, 28% of the responders (9 of 32) initially bivalve (cut the SLN in half), whereas 59% (19 of 32) use a bread loaf technique, cutting the SLN at even intervals without specifically commenting about orientation to the hilum. The number of levels initially cut from the SLN block varied from 1 to 8 levels per block. Thirty-nine percent of the respondents (12 of 31) routinely order immunohistochemistry before evaluation of the initial hematoxylin- and eosin-stained sections. Eighty percent of the respondents (24 of 30) report the maximum dimension of the metastatic tumor deposit. The response rate was low (22%), and most respondents did not indicate how many SLN accessions were performed at their institution each year. Histologic protocols for processing SLNs for MM vary among institutions. Different methods of handling SLNs result in varying sensitivities for detection of metastases. Data derived from these varied approaches to develop and determine prognostic and staging categories may be inconsistent. A standardized yet practical approach is needed to provide reliable information on which prognosis can be determined and therapeutic guidelines can be based. The hope is for dermatologists and those treating patients with MM to understand the intricacies and inconsistencies involved in performance and interpretation of this key staging tool.

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.