Melanoma in Pediatric and Young Adult Patients.

PURPOSE OF REVIEW: Melanoma in younger individuals has different clinical presentations, histologic characteristics and prognosis from older patients. This review summarizes key differences and important new insights into pediatric and young adult melanoma, as well as recent evolutions in treatment. RECENT FINDINGS: Molecular techniques have improved the classification of melanocytic neoplasms, and are especially useful in the workup of the diagnostically challenging lesions frequent in this age group. Molecular evaluation highlights differences between melanoma and atypical lesions with Spitz-like morphology, and should routinely be incorporated for diagnosing and classifying Spitzoid melanocytic to guide prognostication and treatment. Once diagnosed, the management of bona fide melanoma in children and young adults is largely similar to older patients, while the optimal management of lesions such as atypical Spitz tumors remains uncertain. Increased awareness of the presentation and diagnostic characteristics of melanoma in young individuals will allow earlier detection, and improved diagnostic techniques will allow optimum management without over- or under-treatment.

Androgen drives melanoma invasiveness and metastatic spread by inducing tumorigenic fucosylation.

Melanoma incidence and mortality rates are historically higher for men than women. Although emerging studies have highlighted tumorigenic roles for the male sex hormone androgen and its receptor (AR) in melanoma, cellular and molecular mechanisms underlying these sex-associated discrepancies are poorly defined. Here, we delineate a previously undisclosed mechanism by which androgen-activated AR transcriptionally upregulates fucosyltransferase 4 (FUT4) expression, which drives melanoma invasiveness by interfering with adherens junctions (AJs). Global phosphoproteomic and fucoproteomic profiling, coupled with in vitro and in vivo functional validation, further reveal that AR-induced FUT4 fucosylates L1 cell adhesion molecule (L1CAM), which is required for FUT4-increased metastatic capacity. Tumor microarray and gene expression analyses demonstrate that AR-FUT4-L1CAM-AJs signaling correlates with pathological staging in melanoma patients. By delineating key androgen-triggered signaling that enhances metastatic aggressiveness, our findings help explain sex-associated clinical outcome disparities and highlight AR/FUT4 and its effectors as potential prognostic biomarkers and therapeutic targets in melanoma.

Differential histone acetylation and super-enhancer regulation underlie melanoma cell dedifferentiation.

Dedifferentiation or phenotype switching refers to the transition from a proliferative to an invasive cellular state. We previously identified a 122-gene epigenetic gene signature that classifies primary melanomas as low versus high risk (denoted as Epgn1 or Epgn3). We found that the transcriptomes of the Epgn1 low-risk and Epgn3 high-risk cells are similar to the proliferative and invasive cellular states, respectively. These signatures were further validated in melanoma tumor samples. Examination of the chromatin landscape revealed differential H3K27 acetylation in the Epgn1 low-risk versus Epgn3 high-risk cell lines that corroborated with a differential super-enhancer and enhancer landscape. Melanocytic lineage genes (MITF, its targets and regulators) were associated with super-enhancers in the Epgn1 low-risk state, whereas invasiveness genes were linked with Epgn3 high-risk status. We identified the ITGA3 gene as marked by a super-enhancer element in the Epgn3 invasive cells. Silencing of ITGA3 enhanced invasiveness in both in vitro and in vivo systems, suggesting it as a negative regulator of invasion. In conclusion, we define chromatin landscape changes associated with Epgn1/Epgn3 and phenotype switching during early steps of melanoma progression that regulate transcriptional reprogramming. This super-enhancer and enhancer-driven epigenetic regulatory mechanism resulting in major changes in the transcriptome could be important in future therapeutic targeting efforts.

Grade of Primary Cutaneous Leiomyosarcoma Dictates Risk for Metastatic Spread and Disease-Specific Mortality.

BACKGROUND AND OBJECTIVES: Primary cutaneous leiomyosarcoma (cLMS), a rare, typically intradermal tumor, has previously been reported to exhibit an indolent course of disease with zero-to-low risk of local recurrence or distant metastasis. This study seeks to evaluate recurrence and survival of cLMS patients through study of its clinicopathologic and treatment characteristics. METHODS: All patients included underwent resection of primary cLMS at this institution between 2006 and 2019. A retrospective cohort study analysis of clinicopathologic characteristics, treatment, recurrence, and overall survival was performed. Data was assessed through descriptive statistics and outcome measures assessed by Cox proportional models and log-rank tests. RESULTS: Eighty-eight patients with cLMS were evaluated. The majority were men (n = 68, 77%) and Caucasian (n = 85, 97%), with median age at diagnosis of 66 years (range 20-96). 65% of tumors were located on the extremities, with a median size of 1.3 cm (range .3-15). Assessment revealed low (n = 41, 47%), intermediate (n = 29, 33%), and high (n = 18, 20%) grade tumors, demonstrating extension into subcutaneous tissue in 38/60 (60%), with 3 patients exhibiting extension into muscle (3%). All underwent resection as primary treatment with median 1 cm margins (range .5-2). With median follow-up of 27.5 months (IQR 8-51; range 1-131), no low-grade cases had recurrence or death while there was a recurrence rate of 19.1% (9/47) and death rate of 8.5% (4/47) in intermediate- to high-grade cases. CONCLUSIONS: Primary tumor resection of cLMS provides excellent local control for low-grade tumors as no low-grade cases experienced recurrence. For patients with intermediate- to high-grade tumors, there is potential for local recurrence, distant metastasis, and death, and therefore surveillance following treatment is encouraged.

Neoantigen-specific CD4+ tumor-infiltrating lymphocytes are potent effectors identified within adoptive cell therapy products for metastatic melanoma patients.

BACKGROUND: Adoptive cell therapy (ACT) with tumor-infiltrating lymphocytes (TILs) is a promising immunotherapeutic approach for patients with advanced solid tumors. While numerous advances have been made, the contribution of neoantigen-specific CD4+T cells within TIL infusion products remains underexplored and therefore offers a significant opportunity for progress. METHODS: We analyzed infused TIL products from metastatic melanoma patients previously treated with ACT for the presence of neoantigen-specific T cells. TILs were enriched on reactivity to neoantigen peptides derived and prioritized from patient sample-directed mutanome analysis. Enriched TILs were further investigated to establish the clonal neoantigen response with respect to function, transcriptomics, and persistence following ACT. RESULTS: We discovered that neoantigen-specific TIL clones were predominantly CD4+ T cells and were present in both therapeutic responders and non-responders. CD4+ TIL demonstrated an effector T cell response with cytotoxicity toward autologous tumor in a major histocompatibility complex class II-dependent manner. These results were validated by paired TCR and single cell RNA sequencing, which elucidated transcriptomic profiles distinct to neoantigen-specific CD4+ TIL. CONCLUSIONS: Despite methods which often focus on CD8+T cells, our study supports the importance of prospective identification of neoantigen-specific CD4+ T cells within TIL products as they are a potent source of tumor-specific effectors. We further advocate for the inclusion of neoantigen-specific CD4+ TIL in future ACT protocols as a strategy to improve antitumor immunity.

Acral melanoma: clinical advances and hope for the future.

Acral melanoma is a rare subtype of melanoma with unique histologic and biologic characteristics. Given its relative rarity compared with nonacral cutaneous melanoma, acral melanoma has been understudied and underrepresented in modern-day prospective clinical trials that have shaped the contemporary management of advanced cutaneous melanoma. Therefore, treatment principles for advanced acral melanoma are mostly derived from retrospective analyses or extrapolated from data largely based on nonacral cutaneous melanoma. Further studies are warranted to evaluate the efficacy of systemic immune and targeted molecular therapies, and to identify molecular targets for patients with advanced acral melanoma.

Circulating tumor DNA-based molecular residual disease detection for treatment monitoring in advanced melanoma patients.

BACKGROUND: Immune checkpoint inhibitors (ICIs) have substantially improved overall survival in patients with advanced melanoma; however, the lack of biomarkers to monitor treatment response and relapse remains an important clinical challenge. Thus, a reliable biomarker is needed that can risk-stratify patients for disease recurrence and predict response to treatment. METHODS: A retrospective analysis using a personalized, tumor-informed circulating tumor DNA (ctDNA) assay on prospectively collected plasma samples (n = 555) from 69 patients with advanced melanoma was performed. Patients were divided into three cohorts: cohort A (N = 30), stage III patients receiving adjuvant ICI/observation; cohort B (N = 29), unresectable stage III/IV patients receiving ICI therapy; and cohort C (N = 10), stage III/IV patients on surveillance after planned completion of ICI therapy for metastatic disease. RESULTS: In cohort A, compared to molecular residual disease (MRD)-negative patients, MRD-positivity was associated with significantly shorter distant metastasis-free survival (DMFS; hazard ratio [HR], 10.77; p = .01). Increasing ctDNA levels from the post-surgical or pre-treatment time point to after 6 weeks of ICI were predictive of shorter DMFS in cohort A (HR, 34.54; p < .0001) and shorter progression-free survival (PFS) in cohort B (HR, 22; p = .006). In cohort C, all ctDNA-negative patients remained progression-free for a median follow-up of 14.67 months, whereas ctDNA-positive patients experienced disease progression. CONCLUSION: Personalized and tumor-informed longitudinal ctDNA monitoring is a valuable prognostic and predictive tool that may be used throughout the clinical course of patients with advanced melanoma.

Atypical Fibroxanthoma: Outcomes from a Large Single Institution Series.

BACKGROUND: Atypical fibroxanthomas (AFX) are rare malignant cutaneous neoplasms. Unfortunately, limited clinicopathologic and outcomes data on this cancer exists. OBJECTIVE: We report the clinical, pathologic, and treatment characteristics, as well as oncologic outcomes in this single-institution retrospective analysis. METHODS: This retrospective cohort study compiled clinical, pathologic, treatment, and outcome data for all patients with AFX on definitive excision diagnosed, evaluated, and treated primarily by surgical resection at a single institution between 2000-2020. Descriptive statistics evaluated clinical and pathologic characteristics. Kaplan-Meier method and Cox proportional-hazards models were used to evaluate overall survival and recurrence-free survival. RESULTS: 78 patients with AFX were identified. The majority were elderly, immunocompetent, Caucasian men. 85% of tumors were located on the head and neck. 63% of patients were correctly diagnosed only after complete resection of the index lesion. The median surgical margin was 1.0 cm. Overall, only 1.3% (1/78) of patients developed a local recurrence (RFS). No patients died of disease. CONCLUSION: This study suggests that resection margins of 1 cm achieve excellent local control with close to 99% RFS and 100% disease-specific survival.

Interobserver agreement in the histopathological classification of desmoplastic melanomas.

Desmoplastic melanoma is a subtype of melanoma characterised by amelanotic fusiform melanocytes dispersed in a collagenous stroma. Cell-poor and fibrous stroma-rich 'pure' variants have been distinguished from 'mixed' variants with areas of higher cell density and/or less desmoplastic stroma. This distinction is relevant because patients whose tumours display a pure phenotype have a lower risk for regional lymph node metastasis and distant recurrence. However, little is known about interobserver agreement among pathologists in the subclassification of desmoplastic melanoma. To address this issue, we conducted a study in which eleven dermatopathologists independently evaluated whole slide scanned images of excisions from 30 desmoplastic melanomas. The participating pathologists were asked to classify the tumours as pure or mixed. They were also asked to record the presence or absence of neurotropism and angiotropism. We found substantial interobserver agreement between the 11 dermatopathologists in the classification of tumours as pure versus mixed desmoplastic melanoma (kappa=0.64; p<0.0001). There was fair agreement between the 11 dermatopathologists in the evaluation of presence versus absence of neurotropism (kappa=0.26; p<0.0001), and slight agreement in the assessment of angiotropism (kappa=0.13; p<0.0001). The level of concordance in the subclassification of desmoplastic melanomas is encouraging for the acceptance of this prognostic parameter in the real-world practice of melanoma pathology.

Combined nivolumab and ipilimumab with or without stereotactic body radiation therapy for advanced Merkel cell carcinoma: a randomised, open label, phase 2 trial.

BACKGROUND: Merkel cell carcinoma is among the most aggressive and lethal of primary skin cancers, with a high rate of distant metastasis. Anti-programmed death receptor 1 (anti-PD-1) and programmed death ligand 1 (PD-L1) monotherapy is currently standard of care for unresectable, recurrent, or metastatic Merkel cell carcinoma. We assessed treatment with combined nivolumab plus ipilimumab, with or without stereotactic body radiotherapy (SBRT) in patients with advanced Merkel cell carcinoma as a first-line therapy or following previous treatment with anti-PD-1 and PD-L1 monotherapy. METHODS: In this randomised, open label, phase 2 trial, we randomly assigned adults from two cancer sites in the USA (one in Florida and one in Ohio) to group A (combined nivolumab and ipilimumab) or group B (combined nivolumab and ipilimumab plus SBRT) in a 1:1 ratio. Eligible patients were aged at least 18 years with histologically proven advanced stage (unresectable, recurrent, or stage IV) Merkel cell carcinoma, a minimum of two tumour lesions measureable by CT, MRI or clinical exam, and tumour tissue available for exploratory biomarker analysis. Patients were stratified by previous immune-checkpoint inhibitor (ICI) status to receive nivolumab 240 mg intravenously every 2 weeks plus ipilimumab 1 mg/kg intravenously every 6 weeks (group A) or the same schedule of combined nivolumab and ipilimumab with the addition of SBRT to at least one tumour site (24 Gy in three fractions at week 2; group B). Patients had to have at least two measurable sites of disease so one non-irradiated site could be followed for response. The primary endpoint was objective response rate (ORR) in all randomly assigned patients who received at least one dose of combined nivolumab and ipilimumab. ORR was defined as the proportion of patients with a complete response or partial response per immune-related Response Evaluation Criteria in Solid Tumours. Response was assessed every 12 weeks. Safety was assessed in all patients. This trial is registered with ClinicalTrials.gov, NCT03071406. FINDINGS: 50 patients (25 in both group A and group B) were enrolled between March 14, 2017, and Dec 21, 2021, including 24 ICI-naive patients (13 [52%] of 25 group A patients and 11 [44%] of 25 group B patients]) and 26 patients with previous ICI (12 [48%] of 25 group A patients and 14 [56%] of 25 group B patients]). One patient in group B did not receive SBRT due to concerns about excess toxicity. Median follow-up was 14·6 months (IQR 9·1-26·5). Two patients in group B were excluded from the analysis of the primary endpoint because the target lesions were irradiated and so the patients were deemed non-evaluable. Of the ICI-naive patients, 22 (100%) of 22 (95% CI 82-100) had an objective response, including nine (41% [95% CI 21-63]) with complete response. Of the patients who had previously had ICI exposure, eight (31%) of 26 patients (95% CI 15-52) had an objective response and four (15% [5-36]) had a complete response. No significant differences in ORR were observed between groups A (18 [72%] of 25 patients) and B (12 [52%] of 23 patients; p=0·26). Grade 3 or 4 treatment-related adverse events were observed in 10 (40%) of 25 patients in group A and 8 (32%) of 25 patients in group B. INTERPRETATION: First-line combined nivolumab and ipilimumab in patients with advanced Merkel cell carcinoma showed a high ORR with durable responses and an expected safety profile. Combined nivolumab and ipilimumab also showed clinical benefit in patients with previous anti-PD-1 and PD-L1 treatment. Addition of SBRT did not improve efficacy of combined nivolumab and ipilimumab. The combination of nivolumab and ipilimumab represents a new first-line and salvage therapeutic option for advanced Merkel cell carcinoma. FUNDING: Bristol Myers Squibb Rare Population Malignancy Program.

Current and future approaches in the surgical management of T3b/T4 primary and locoregionally advanced melanoma.

Currently accepted principles of surgical management-margin width, use of sentinel node biopsy, performance of radical node dissections for node-positive cases-and some aspects of postoperative management (use of radiation for desmoplastic melanoma primaries and for clinically node-positive disease) will change in the future with the potential widespread adoption of adjuvant and neoadjuvant therapies.

Genomic and Single-Cell Landscape Reveals Novel Drivers and Therapeutic Vulnerabilities of Transformed Cutaneous T-cell Lymphoma.

ABSTRACT: Cutaneous T-cell lymphoma (CTCL) is a rare cancer of skin-homing T cells. A subgroup of patients develops large cell transformation with rapid progression to an aggressive lymphoma. Here, we investigated the transformed CTCL (tCTCL) tumor ecosystem using integrative multiomics spanning whole-exome sequencing (WES), single-cell RNA sequencing, and immune profiling in a unique cohort of 56 patients. WES of 70 skin biopsies showed high tumor mutation burden, UV signatures that are prognostic for survival, exome-based driver events, and most recurrently mutated pathways in tCTCL. Single-cell profiling of 16 tCTCL skin biopsies identified a core oncogenic program with metabolic reprogramming toward oxidative phosphorylation (OXPHOS), cellular plasticity, upregulation of MYC and E2F activities, and downregulation of MHC I suggestive of immune escape. Pharmacologic perturbation using OXPHOS and MYC inhibitors demonstrated potent antitumor activities, whereas immune profiling provided in situ evidence of intercellular communications between malignant T cells expressing macrophage migration inhibitory factor and macrophages and B cells expressing CD74. SIGNIFICANCE: Our study contributes a key resource to the community with the largest collection of tCTCL biopsies that are difficult to obtain. The multiomics data herein provide the first comprehensive compendium of genomic alterations in tCTCL and identify potential prognostic signatures and novel therapeutic targets for an incurable T-cell lymphoma. This article is highlighted in the In This Issue feature, p. 1171.

Single-cell Characterization of the Cellular Landscape of Acral Melanoma Identifies Novel Targets for Immunotherapy.

PURPOSE: Acral melanoma is a rare subtype of melanoma that arises on the non-hair-bearing skin of the palms, soles, and nail beds. In this study, we used single-cell RNA sequencing (scRNA-seq) to map the transcriptional landscape of acral melanoma and identify novel immunotherapeutic targets. EXPERIMENTAL DESIGN: We performed scRNA-seq on nine clinical specimens (five primary, four metastases) of acral melanoma. Detailed cell type curation was performed, the immune landscapes were mapped, and key results were validated by analysis of The Cancer Genome Atlas (TCGA) and single-cell datasets. Cell-cell interactions were inferred and compared with those in nonacral cutaneous melanoma. RESULTS: Multiple phenotypic subsets of T cells, natural killer (NK) cells, B cells, macrophages, and dendritic cells with varying levels of activation/exhaustion were identified. A comparison between primary and metastatic acral melanoma identified gene signatures associated with changes in immune responses and metabolism. Acral melanoma was characterized by a lower overall immune infiltrate, fewer effector CD8 T cells and NK cells, and a near-complete absence of γδ T cells compared with nonacral cutaneous melanomas. Immune cells associated with acral melanoma exhibited expression of multiple checkpoints including PD-1, LAG-3, CTLA-4, V-domain immunoglobin suppressor of T cell activation (VISTA), TIGIT, and the Adenosine A2A receptor (ADORA2). VISTA was expressed in 58.3% of myeloid cells and TIGIT was expressed in 22.3% of T/NK cells. CONCLUSIONS: Acral melanoma has a suppressed immune environment compared with that of cutaneous melanoma from nonacral skin. Expression of multiple, therapeutically tractable immune checkpoints were observed, offering new options for clinical translation.

Is the presence of tumor-infiltrating lymphocytes predictive of outcomes in patients with melanoma?

BACKGROUND: The significance of tumor-infiltrating lymphocytes (TILs) in melanoma is debated. This article presents a multicenter, retrospective study assessing the predictive and prognostic value of TILs. METHODS: The Sentinel Lymph Node Working Group database was queried from 1993 to 2018 for cases with known TIL data. TILs were categorized as absent or present, which included nonbrisk (NB), brisk (B), and present but unspecified TIL levels. Clinicopathologic factors were correlated with TILs, sentinel lymph node (SLN) status, and melanoma-specific survival (MSS). RESULTS: Overall, 3203 patients were included. The median thickness was 1.5 mm, and 469 cases had SLN metastases. TILs were present in 2458 cases (76.7%), with NB, B, and unspecified TILs seen in 1691 (68.8%), 691 (28.1%), and 76 (3.1%), respectively. Multivariable analysis showed that the presence of TILs significantly predicted a negative SLN biopsy (P < .05). The median follow-up was 25.2 months. MSS was significantly better for cases with TILs than cases without TILs (P < .001). According to multivariable analysis, age, gender, thickness, mitotic rate, ulceration, lymphovascular invasion, and SLN status were significantly prognostic of MSS (all P values < .05). Although TILs were not prognostic of MSS, when multiple imputation was used and the SLN status was excluded, the presence of TILs was significantly prognostic of improved MSS (hazard ratio, 0.78; 95% confidence interval, 0.64-0.95; P = .0154). CONCLUSIONS: TILs are a favorable marker because their presence significantly predicts a negative SLN, and the absence of TILs may be a prognostic marker of worse survival in patients with a positive SLN but not a negative SLN. TILs may also serve as a prognostic marker of survival when the SLN status is not considered.

Is There a Relationship Between TILs and Regression in Melanoma?

BACKGROUND: The relationship between tumor-infiltrating lymphocytes (TILs) and regression in melanoma is unknown. This report describes a large multicenter study assessing the association between TILs and regression. METHODS: The Sentinel Lymph Node Working Group database was queried from 1993 to 2018 for cases with TILs and regression data. Clinicopathologic factors were correlated with regression and TIL status, sentinel lymph node (SLN) status, and overall survival (OS). RESULTS: The study enrolled 2450 patients. In 1811 cases, TILs (73.9%) were present, with regression present in 328 of these 1811 (18.1%) cases and in 49 (7.7%) of 639 cases without TILs. The presence of TILs was significantly associated with regression (p < 0.0001) as well as a negative SLN (p < 0.05). However, when TILs were stratified by regression status, only absence or presence of both TILs and regression were significantly associated with SLN metastases (p = 0.038). Although the presence of TILs was associated with OS (p < 0.05), regression status by itself was not (p = 0.2058 and 0.252, respectively). Furthermore, when TILs were stratified by regression status, only the presence of TILs with or without regression was significantly associated with improved OS (p = 0.0081 and 0.0137, respectively) versus the absence of both TILs and regression, with regression status not significantly affecting OS for patients with or without TILs (p = 0.2314 and 0.65, respectively). CONCLUSIONS: Regression is highly correlated with TILs, but only TILs are significantly associated with SLN metastasis and OS in melanoma patients, whereas regression is not. The impact of regression on outcomes ultimately appears dependent upon the absence or presence of TILs.

Natural History of Incident and Persistent Cutaneous Human Papillomavirus and Human Polyomavirus Infections.

BACKGROUND: Cutaneous human papillomaviruses (cuHPV) and polyomaviruses (HPyV) have been implicated in skin cancers; however, interpretation of findings across studies is complicated by limited understanding of the natural history of these infections across normal tissue types. METHODS: In total, 675 eyebrow hair (EBH) and skin swab (SSW) samples were collected from 71 skin cancer screening patients every 6 months over 2 years and measured for presence of ß-HPV, γ-HPV, and HPyV. Incidence, persistence, and clearance of cuHPV/HPyV were estimated, and risk factors associated with infection were examined. RESULTS: Prevalence, incidence, and persistence of ß-HPV, γ-HPV, and HPyV were consistently higher in SSW than in EBH, with types 5, 24, 49, 76 and Merkel cell polyomavirus (MCPyV) having incidence rates greater than 20 per 1000 person-months. Prevalent γ-HPV EBH infections persisted more often in women (P = .024), incident ß-HPV EBH infections persisted less often among individuals with history of blistering sunburn (P = .019), and prevalent MCPyV SSW infections persisted more often in those with a history of skin cancer (P = .033). CONCLUSIONS: Incidence and persistence of cuHPV/HPyV were observed in SSW and EBH; however, none of the risk factors examined were commonly associated with cuHPV/HPyV infections across normal tissue types.

Regression in melanoma is significantly associated with a lower regional recurrence rate and better recurrence-free survival.

BACKGROUND AND OBJECTIVES: The prognostic significance of regression in predicting melanoma recurrences is unknown. We present a large multicenter study correlating regression with recurrence. METHODS: The Sentinel Lymph Node Working Group database was queried from 1993 to 2018 for cases with regression data. Clinicopathologic factors were correlated with overall and first-site of recurrence and with recurrence-free survival (RFS). RESULTS: There were 4790 patients and the median follow-up was 39.6 months. Regression and recurrences were seen in 1081 (22.6%) and 773 (16.1%) cases, respectively. First-site locoregional and distant recurrences were seen in 412 (8.6%) and 352 (7.3%) patients, respectively. Regression was seen in 15.8% and 24.7% of all cases with and without recurrences (p < 0.0001), respectively, while regression was seen in 14.3% and 17.9% of first-site locoregional and distant recurrent cases, respectively, compared with 23.3% and 22.9% of patients with regression and without first-site locoregional and distant recurrences, respectively (p = 0.29). On multivariable analysis, after controlling for age, gender, thickness, ulceration, lymphovascular invasion, and sentinel lymph node status, regression significantly predicted improved RFS (p = 0.004) and fewer first-site regional recurrences (p = 0.017). CONCLUSION: Our data suggest that regression is a favorable prognostic marker in melanoma and predicts significantly better RFS and decreased first-site regional recurrences.

Detection of cancer metastasis: past, present and future.

The clinical importance of metastatic spread of cancer has been recognized for centuries, and melanoma has loomed large in historical descriptions of metastases, as well as the numerous mechanistic theories espoused. The "fatal black tumor" described by Hippocrates in 5000 BC that was later termed "melanose" by Rene Laennec in 1804 was recognized to have the propensity to metastasize by William Norris in 1820. And while the prognosis of melanoma was uniformly acknowledged to be dire, Samuel Cooper described surgical removal as having the potential to improve prognosis. Subsequent to this, in 1898 Herbert Snow was the first to recognize the potential clinical benefit of removing clinically normal lymph nodes at the time of initial cancer surgery. In describing "anticipatory gland excision," he noted that "it is essential to remove, whenever possible, those lymph glands which first receive the infective protoplasm, and bar its entrance into the blood, before they have undergone increase in bulk". This revolutionary concept marked the beginning of a debate that rages today: are regional lymph nodes the first stop for metastases ("incubator" hypothesis) or does their involvement serve as an indicator of aggressive disease with inherent metastatic potential ("marker" hypothesis). Is there a better way to improve prediction of disease outcome? This article attempts to address some of the resultant questions that were the subject of the session "Novel Frontiers in the Diagnosis of Cancer" at the 8th International Congress on Cancer Metastases, held in San Francisco, CA in October 2019. Some of these questions addressed include the significance of sentinel node metastasis in melanoma, and the optimal method for their pathologic analysis. The finding of circulating tumor cells in the blood may potentially supplant surgical techniques for detection of metastatic disease, and we are beginning to perfect techniques for their detection, understand how to apply the findings clinically, and develop clinical followup treatment algorithms based on these results. Finally, we will discuss the revolutionary field of machine learning and its applications in cancer diagnosis. Computer-based learning algorithms have the potential to improve efficiency and diagnostic accuracy of pathology, and can be used to develop novel predictors of prognosis, but significant challenges remain. This review will thus encompass latest concepts in the detection of cancer metastasis via the lymphatic system, the circulatory system, and the role of computers in enhancing our knowledge in this field.

Circulating Immunosuppressive Regulatory T Cells Predict Risk of Incident Cutaneous Squamous Cell Carcinoma.

Ultraviolet radiation exposure (UVR) is a risk factor for cutaneous squamous cell carcinoma (cuSCC) and has been shown to be positively associated with circulating immunosuppressive regulatory T cells ("Tregs"). However, the risk of cuSCC in association with circulating Tregs has not been studied. The aim of this study was to determine whether circulating Treg levels are associated with cuSCC development, particularly in the context of high UVR. Blood and spectrophotometer-based UVR measurements were obtained on 327 immunocompetent individuals undergoing routine skin cancer screenings at baseline and followed for up to 4 years for incident cuSCC development within a prospective cohort study. Proportions of phenotypically distinct Tregs, especially CCR4hi and CLA+ cells which are associated with activation and homing, respectively, were measured by flow cytometry. Tregs in cuSCC tumors were assessed using immunohistochemistry and graded for solar elastosis, a measure of cumulative UVR damage. Of several Treg phenotypes examined, higher levels of circulating CCR4hi Tregs at baseline were significantly associated with increased risk of subsequent cuSCC; those with higher levels of both CCR4hi and UVR were four times more likely to develop cuSCC compared to those with lower levels of both (Hazard Ratio = 4.11, 95% CI = 1.22-13.90). Within cuSCC tumors, CCR4hi Tregs were positively associated with solar elastosis. Results show that a higher proportion of CCR4hi peripheral Tregs predicts incident cuSCC up to 4 years, especially among highly UV-exposed individuals. Research of the underpinning biology of Tregs in UVR-associated skin damage may possibly reveal novel opportunities for screening, prevention, and treatment.

Cutaneous Human Papillomaviruses and the Risk of Keratinocyte Carcinomas.

Cutaneous human papillomavirus (cuHPV) infections may be novel targets for skin cancer prevention and treatment, but critical information regarding the development of virus-positive skin cancers following cuHPV infection has been lacking. In this study, baseline cuHPV infection was measured by serology and viral DNA detection in eyebrow hairs (EBH) and forearm skin swabs (SSW) among 1,008 individuals undergoing routine skin cancer screening exams and followed for incidence of basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cuSCC). Baseline ß-HPV detection, particularly in SSW, significantly predicted cuSCC (HR = 4.32; 95% confidence interval, 1.00-18.66), whereas serologic evidence of past ß-HPV infection was not associated with cuSCC. Less than 5% of baseline ß-HPV types detected in SSW were present in subsequent cuSCC tumors, and cuHPV detected in SSW with higher mean fluorescence intensity values were more likely to be present in cuSCC compared with those with lower levels (P < 0.001). ß-HPV-positive cuSCC occurred more often in areas of highly sun-damaged skin than did ß-HPV-negative cuSCC. Overall, no clear patterns were observed between baseline ß-HPV detection and subsequent development of BCC, or between baseline γ-HPV detection and either cuSCC or BCC. Collectively, these results demonstrate that ß-HPV detection in SSW is a significant predictor of cuSCC risk, although evidence suggests only a small subset of cuSCC is etiologically linked to ß-HPV infection. SIGNIFICANCE: ß-HPV positivity may be a useful biomarker for identifying individuals who could benefit from increased screening or novel cutaneous squamous cell carcinoma prevention strategies.