The role of cyclin D1 and Ki-67 in the development and prognostication of thin melanoma.

AIMS: Despite their low individual metastatic potential, thin melanomas (≤1 mm Breslow thickness) contribute significantly to melanoma mortality overall. Therefore, identification of prognostic biomarkers is particularly important in this subgroup of melanoma. Prompted by preclinical results, we investigated cyclin D1 protein and Ki-67 expression in in-situ, metastatic and non-metastatic thin melanomas. METHODS AND RESULTS: Immunohistochemistry was performed on 112 melanoma specimens, comprising 22 in situ, 48 non-metastatic and 42 metastatic thin melanomas. Overall, epidermal and dermal cyclin D1 and Ki-67 expression were semiquantitatively evaluated by three independent investigators and compared between groups. Epidermal Ki-67 expression did not differ statistically in in-situ and invasive melanoma (P = 0.7). Epidermal cyclin D1 expression was significantly higher in thin invasive than in in-situ melanoma (P = 0.003). No difference was found in cyclin D1 expression between metastatic and non-metastatic invasive tumours. Metastatic and non-metastatic thin melanomas did not show significant differences in epidermal expression of Ki-67 and cyclin D1 (P = 0.148 and P = 0.611, respectively). In contrast, strong dermal expression of Ki-67 was more frequent in metastatic than non-metastatic samples (28.6 versus 8.3%, respectively, P = 0.001). The prognostic value of dermal Ki-67 expression was confirmed by multivariate analysis (P = 0.047). CONCLUSION: We found an increased expression of cyclin D1 in invasive thin melanomas compared to in-situ melanomas, which supports a potential role of this protein in early invasion in melanoma, as suggested by preclinical findings. Moreover, our results confirm that high dermal Ki-67 expression is associated with an increased risk of development of metastasis in thin melanoma and could possibly serve as a prognostic biomarker in clinical practice, especially if combined with additional methods.

A nomogram to predict node positivity in patients with thin melanomas helps inform shared patient decision making.

OBJECTIVE: To develop a nomogram to estimate the probability of positive sentinel lymph node (+SLN) for patients with thin melanoma and to characterize its potential impact on sentinel lymph node biopsy (SLNB) rates. METHODS: Patients diagnosed with thin (0.5-1.0 mm) melanoma were identified from the National Cancer Database 2012 to 2015. A multivariable logistic regression model was used to examine factors associated with +SLN, and a nomogram to predict +SLN was constructed. Nomogram performance was evaluated and diagnostic test statistics were calculated. RESULTS: Of the 21 971 patients included 10 108 (46.0%) underwent SLNB, with a 4.0% +SLN rate. On multivariable analysis, age, Breslow thickness, lymphovascular invasion, ulceration, and Clark level were significantly associated with SLN status. The area under the receiver operating curve was 0.67 (95% confidence interval, 0.65-0.70). While 15 249 (69.4%) patients had either T1b tumors or T1a tumors with at least one adverse feature, only 2846 (13.0%) had a nomogram predicted probability of a +SLN ≥5%. Using this cut-off, the indication for a SLNB in these patients would be reduced by 81.3% as compared to the American Joint Committee on Cancer 8th edition staging criteria. CONCLUSIONS: The risk predictions obtained from the nomogram allow for more accurate selection of patients who could benefit from SLNB.

Disease-Free Survival for Patients with Thin Melanomas according to the American Joint Committee on Cancer 8th Edition.

BACKGROUND: The recently implemented AJCC 8th edition TNM staging system for malignant melanoma (MM) changed the definition for T1a and T1b tumours. OBJECTIVES: To analyse differences in disease-free survival (DFS) among patients with thin MM staged according to both AJCC 7th and 8th editions. METHODS: An observational study including 285 patients with cutaneous thin MM (thickness ≤1 mm). Cases were staged as T1a and T1b using both 7th and 8th editions. Neither regional nor visceral diseases were present at diagnosis. DFS curves were generated according to the Kaplan-Meier method. RESULTS: An 8% shift of patients from a T1a towards a T1b stage group was observed after applying the AJCC 8th edition. According to this 8th edition, DFS for T1a patients was significantly longer than for T1b patients (log-rank test; p = 0.005); 5-year DFS for T1a and T1b was 100 and 95%, respectively (Wilcoxon test; p = 0.002). According to the AJCC 7th edition, DFS did not significantly differ for T1a and T1b patients; 5-year DFS for T1a and T1b was 99 and 97%, respectively (p > 0.05). CONCLUSIONS: The AJCC 8th edition seems to be a better tool for staging thin melanomas.

Sentinel lymph node biopsy in patients with thin melanomas: Frequency and predictors of metastasis based on analysis of two large international cohorts.

BACKGROUND: Sentinel lymph node (SLN) metastasis in patients with thin melanomas (≤1 mm) is uncommon but adverse prognostic factors may indicate an increased risk. We sought to determine how often SLN biopsy (SLNB) was performed in patients with thin melanomas, establish the frequency of SLN metastasis and evaluate the predictive value of ulceration, tumor mitotic rate, and thickness for SLN involvement. METHODS: Melanoma patients with a Breslow thickness greater than or equal to 0.5 to less than or equal to 1 mm, diagnosed 2009-2016, were identified in the Swedish Melanoma Register (SMR) and the Melanoma Institute Australia (MIA) Database. RESULTS: In total 8165 patients were included from the SMR and 1603 from MIA. SLNB was performed in 9.5% and 16.2% of patients, respectively. Corresponding figures for T1b (American Joint Committee on Cancer [AJCC] 7th Edition) were 19.5% and 24.6%. The SLN positivity rate were 4.4% (Sweden) and 5.8% (MIA). SLN metastasis was more frequent in tumors with ulceration, mitoses, and Breslow thickness greater than or equal to 0.9 mm but none were statistically significant. Younger age was identified as a significant risk factor for SLN positivity at MIA. CONCLUSIONS: A minority of patients with thin melanomas had SLNB performed and the SLN positivity rate was low. This study did not confirm tumor ulceration, mitoses, or thickness as statistically significant predictors for SLN metastasis.

Implementation of the 7th edition AJCC staging system: Effects on staging and survival for pT1 melanoma. A Dutch population based study.

In the 7th edition of the AJCC staging system, the mitotic rate criterion replaced Clark level to increase correct classification of high-risk thin melanoma patients (pT1B). Additionally, sentinel node biopsy (SNB) was recommended for nodal staging of pT1B melanomas. The aim of this article was to evaluate the effects on pT1 substaging and clinical implications in the national pT1 melanoma population. All pT1 melanomas diagnosed in the Netherlands between 2003 and 2014 were selected from the Netherlands Cancer Registry (IKNL). Patients were stratified by cohort according to AJCC edition: (1) 2003-2009 (6th ) and (2) 2010-2014 (7th ). Relative survival was calculated to estimate melanoma-specific survival. A total of 29.546 pT1 melanoma patients were included. The pT1b proportion increased from 10.1% in Cohort 1 to 21.5% in Cohort 2. The proportion of performed SNBs per cohort increased: for pT1b melanomas alone from 4.5% to 13.0%. SNB positivity rate decreased from 10.5% to 8.8% for the entire pT1 population, and for pT1b melanomas from 11.3% to 8.6%. At 5 years, the relative survival rate was similar for pT1a and pT1b in both cohorts, namely, pT1a 100% vs pT1b 97% (Cohort 1), and pT1a 100% vs pT1b 98% (Cohort 2). The 7th edition of the AJCC staging system has caused an increased number of patients to undergo SNB, without an increase in SNB positivity rate. Survival between pT1 subgroups remains similar. The mitotic rate criterion for pT1b classification and the recommendation to perform SNB for pT1b melanomas should be reconsidered.

The natural history of thin melanoma and the utility of sentinel lymph node biopsy.

BACKGROUND AND OBJECTIVES: Current literature may overestimate the risk of nodal metastasis from thin melanoma due to reporting of data only from lesions treated with SLNB. Our objective was to define the natural history of thin melanoma, assessing the likelihood of nodal disease, in order to guide selection for SLNB. METHODS: Retrospective review. The primary outcome was the rate of nodal disease. Clinicopathologic factors were evaluated to find associations with nodal disease. RESULTS: Five hundred and twelve lesions, follow up available for 488 (median: 48 months). Lesions treated with WLE/SLNB compared to WLE alone were more likely to have high-risk features. The rate of nodal disease was higher in the WLE/SLNB group (24 positive SLNB, five false-negative SLNB with nodal recurrence: 10.2%) compared to WLE alone (four nodal recurrences: 2.0%). Univariate analysis showed age ≤45, Breslow depth ≥0.85 mm, mitotic rate >1 mm2 , and ulceration were associated with nodal disease. Multivariate analysis confirmed the association of age ≤45 and ulceration. CONCLUSIONS: SLNB for melanoma 0.75-0.99 mm should be considered in patients age ≤45, Breslow depth ≥0.85 mm, mitotic rate >1 mm2 , and/or with ulceration. Thin melanoma <0.85 mm without high-risk features may be treated with WLE alone.

Mortality burden and prognosis of thin melanomas overall and by subcategory of thickness, SEER registry data, 1992-2013.

BACKGROUND: Thin melanomas cause a high death toll despite excellent prognosis. OBJECTIVE: We examined melanoma mortality burden and prognosis by categories of thickness within Surveillance, Epidemiology, and End Results (SEER) 13 Registry 1992-2013. METHODS: We divided 49,319 stage I and II melanoma cases diagnosed between 1992 and 2003 into T1 through T4 and then subdivided T1 into 0.01-0.25 mm, 0.26-0.50 mm, 0.51-0.75 mm, and 0.76-1.00 mm categories. We determined the number and proportion of deaths due to melanoma within 10 years of diagnosis for each thickness category and proportions within T1 subcategories with ulceration. RESULTS: We confirmed prognosis worsened as melanoma thickened from T1 to T4; however, most deaths resulted from melanomas that were diagnosed at the T1 stage. The smallest number of deaths within T1 resulted from 0.01-0.25 mm-thick melanomas; however, the risk for death within 10 years was greater for those diagnosed with melanoma when tumor depth was 0.01-0.25 mm than for those diagnosed when tumor depth was 0.26-0.50 mm. Prognosis worsened with depths starting at 0.51 mm. The pattern within T1 was not explained by ulceration. LIMITATIONS: We did not evaluate melanoma subtype, mitotic rate, or other associated features. CONCLUSION: Thin melanomas are a substantial public health burden. Efforts should be made to diagnose melanoma at the in situ stage.

A retrospective, multicenter analysis of the predictive value of mitotic rate for sentinel lymph node (SLN) positivity in thin melanomas.

BACKGROUND: There is a paucity of studies to substantiate whether the presence of a single mitosis justifies sentinel lymph node (SLN) biopsy (SLNB) in thin melanomas. OBJECTIVE: We sought to determine if mitotic rate is associated with SLNB outcome when taking into account other prognostic factors. METHODS: All cases of melanoma that underwent SLNB in the province of Alberta, Canada, between 2007 and 2013 were reviewed through a provincial tumor database. RESULTS: A total of 1072 patients fulfilled inclusion criteria. When analyzing all melanomas regardless of thickness, mitotic rate was a good predictor of SLN status. When stratified by Breslow thickness, only intermediate melanomas (1.01-2.0 mm) demonstrated a significant relationship between mitotic rate and positive SLN status (P = .010). For melanomas 1 mm or smaller, mitotic rate was not associated with SLN status. A statistically significant interaction was identified between Breslow thickness and mitotic rate such that for decreasing Breslow depth, the effect of mitotic rate on SLNB status diminished (P = .028). LIMITATIONS: The study was retrospective in nature. There is underlying variability in mitotic rate reporting methods over time, and between different dermatopathologists. CONCLUSIONS: Mitotic rate does not have unequivocal utility in predicting SLNB status in thin melanomas. There is a significant interaction between mitotic rate and Breslow depth, such that the predictive value of mitotic rate on SLN positivity may be dependent on Breslow thickness.

Detection of mitotic figures in thin melanomas--immunohistochemistry does not replace the careful search for mitotic figures in hematoxylin-eosin stain.

BACKGROUND: The mitotic rate is an important prognostic criterion in patients with thin melanoma ≤ 1 mm. OBJECTIVE: The aim of this study was to investigate the reproducibility of the mitotic rate in thin melanoma in hematoxylin-eosin (H&E) stain and compare it with the detection of mitotic figures by immunohistochemistry. METHODS: The number of mitoses stated in the routine diagnostic report in 190 pT1 melanomas was compared with the number gained from re-evaluation of H&E sections and the number detected after staining with the mitotic marker, phosphohistone H3 (PHH3). Two different approaches were used for choosing the "hot spot" for evaluation (dermal vs epidermal/dermal). RESULTS: Comparing routine H&E-stained slides with re-evaluation slides, the number of mitotic figures was slightly variable. However, findings did not result in a change of the tumor stage. In 34% of the tumors with dermal mitotic figures on H&E, mitoses could not be found in the corresponding PHH3 slide anymore. In 4% of the cases, stage relevant mitoses could only be found by PHH3 immunohistochemistry. LIMITATION: This is a single center study. CONCLUSION: Immunohistochemical staining for mitotic figures does not replace a careful evaluation of H&E-stained slides. Immunohistochemical detection of mitosis is only an additional tool; the time-saving effect is therefore negligible.

Assessment of tumor mitotic rate in primary cutaneous malignant melanomas 1 mm or less in thickness.

BACKGROUND: Tumor mitotic rate in thin melanomas is recognized as a powerful, independent prognostic factor predicting survival. In nonulcerated cases, the presence of any dermal mitotic activity upstages the disease to pT1b. The extent to which tissue should be histologically examined to assess mitogenicity, however, has not been studied. OBJECTIVE: We sought to determine whether in staging thin melanomas, there is a significant benefit in examining numerous tissue sections containing invasive disease. METHOD: In all, 71 cases of thin cutaneous melanomas diagnosed between January 2012 and June 2013 were identified after a search performed on the Pathlab database. The slides were retrieved and reviewed retrospectively, comparing the identification of the first dermal tumor mitotic figure, if present, at 4 check-points: the first, third, fifth, or tenth tissue section examined. RESULTS: A statistically significant difference in identification of the first dermal mitotic figure was found in examining 1 versus 3 tissue sections (P = .0411). No significant difference was found in examining numerous tissue sections. LIMITATIONS: This was a retrospective study from a single institution with a limited number of participants. CONCLUSION: In staging thin melanomas without ulceration, the optimal number of sections to assess is 3. No additional benefit is gained by examining numerous tissue sections.

A 10-year, single-institution analysis of clinicopathologic features and sentinel lymph node biopsy in thin melanomas.

BACKGROUND: The 2009 American Joint Committee on Cancer criteria for thin cutaneous melanomas recommend staging sentinel lymph node (SLN) biopsy (SLNB) for select stage IB tumors. SLNB in this population remains controversial because of low rates of node positivity and inconsistent prognostic parameters. OBJECTIVE: The purpose of this study was to examine the association between multiple clinicopathologic features and SLNB result, and clinical outcome. METHODS: Clinical and pathologic parameters from patients with melanomas less than or equal to 1.00 mm receiving wide local excision with SLNB at our institution from 2001 through 2010 were recorded. Analysis for any statistically significant relationships between recorded parameters and SLN results and outcome were performed. RESULTS: A total of 189 cases yielded 3 positive SLNBs (1.6%). Disease progression occurred in 6 cases (3.2%). Positive SLNB predicted distant metastasis and death from disease (P = .0017). Mitotic rate was not associated with a positive SLNB result. LIMITATIONS: The follow-up time for this study was limited (mean = 40.7 months). CONCLUSION: Our data confirm a statistically significant relationship between SLNB result and likelihood for distant metastasis in thin melanoma. There was a trend for a relationship between mitotic rate and clinical outcome. This relationship reached statistical significance at a mitotic rate of greater than 3 mitoses/mm(2).

Topographical and Chronological Analysis of Thin Cutaneous Melanoma's Progressions: A Multicentric Study.

A great portion of cutaneous melanoma's diagnoses nowadays is attributed to thin tumors with up to 1 mm in Breslow thickness (hereafter thin CMs), which occasionally metastasize. The objective of this study was to identify thin CM's metastatic patterns from a topographical and chronological standpoint. A total of 204 cases of metastatic thin CMs from five specialized centers were included in the study, and corresponding data were collected (clinical, epidemiological, histopathological information of primary tumor and the number, anatomical site, and time intervals of their progressions). First progressions occurred locally, in regional lymph nodes, and in a distant site in 24%, 15% and 61% of cases, respectively, with a median time to first progression of 3.10 years (IQR: 1.09-5.24). The median elapsed time between the first and second progression and between the second and third progression was 0.82 (IQR: 0.34-1.97) and 0.49 (IQR: 0.21-2.30) years, respectively, while the median survival time was about 4 years since first progression. Furthermore, the sequences of locations and time intervals of the progressions were associated with the clinicopathological and demographic features of the primary tumors along with the features of the preceding progressions. In conclusion, the findings of this study describe the natural history of thin CMs, thus highlighting the necessity to identify subgroups of thin CMs at a higher risk for metastasis and contributing to the optimization of the management and follow-up of thin CM patients.

Mitotic rate as a predictive factor for positive sentinel lymph nodes in pT1 and pT2 melanomas.

Sentinel lymph node biopsy is a crucial step in the management of patients affected by melanoma. The decision whether to perform it or not is based on different histological parameters, but the mitotic rate is no longer considered a prognostic variable after the release of the 8th edition of the American Joint Committee on Cancer (AJCC) guidelines. Our objective was to investigate the risk factors that increase the chance for sentinel lymph node positivity in melanomas with a Breslow thickness of less than 2.00 mm, including the mitotic count. A retrospective single-center study was performed on a homogenous cohort of 408 patients treated for cutaneous melanoma. Histological and clinical features were gathered and correlated with the increased risk for sentinel lymph node positivity by means of univariate and multivariate analyses. A statistically significant correlation between a high mitotic index and a positive sentinel lymph node was found in pT1 and pT2 patients, suggesting that in the case of pT1a melanoma with a high number of mitoses, a discussion about whether a sentinel lymph node biopsy is required should be done.

The prognostic significance of the clinical and histological parameters in primary cutaneous melanoma patients.

Cutaneous melanoma is the most aggressive form of skin cancer and its incidence is unfortunately increasing. In the last decades, a progressive increase of new cases of diagnosed thin melanoma has been noted. This may be due to earlier detection, better surveillance, improved diagnostic criteria or increased exposure to sunlight. Despite the fact that Breslow tumor thickness has the strongest proven prognostic significance, there are still thin melanomas that metastasize and thick melanomas with favorable evolution. Therefore, the identification of strong predictive factors for survival is mandatory, particularly for patients with thin melanoma.

Risk factors and patterns of recurrence after sentinel lymph node biopsy for thin melanoma.

While having a thin melanoma (defined as AJCC 8 T1 stage tumor ≤ 1.0 mm) with negative sentinel lymph node biopsy (SLNB) provides an excellent prognosis, some patients still develop recurrence and die. To determine risk factors for any recurrence (local/in-transit, nodal, distant) in thin melanoma patients with negative SLNB and assess survival outcomes. Retrospective review of thin melanomas with negative SLNB from 1999 to 2018 was performed. Two hundred and nine patients were identified. Clinicopathologic characteristics of the primary melanoma were collected. Patterns of recurrence for local/in-transit, nodal or distant recurrence and survival outcomes were analyzed. Eighteen patients (8.6%) developed recurrence: 3 (1.9%) local/in-transit, 4 (2.9%) regional/nodal, and 11 (5.3%) distant recurrence during a median follow-up time of 62 months. A multivariate Cox regression model showed that head and neck site (HR 3.52), ulceration (HR 10.8), and mitotic rate (HR 1.39) were significant risk factors for recurrence. Median time to first recurrence was 49 months. Patients with recurrence had a significantly worse 5 year overall survival than those without recurrence (82.2 vs 99.2%). A retrospective single center study and limited sample size. Did not factor in possible false negative SLNBs when calculating hazard ratios. For thin melanoma patients with negative SLNB, heightened surveillance is warranted for those with ulceration, primary tumor location on the head or neck, and elevated mitotic rate.

Predictive Values of Pathological and Clinical Risk Factors for Positivity of Sentinel Lymph Node Biopsy in Thin Melanoma: A Systematic Review and Meta-Analysis.

BACKGROUND: The indications for sentinel lymph node biopsy (SLNB) for thin melanoma are still unclear. This meta-analysis aims to determine the positive rate of SLNB in thin melanoma and to summarize the predictive value of different high-risk features for positive results of SLNB. METHODS: Four databases were searched for literature on SLNB performed in patients with thin melanoma published between January 2000 and December 2020. The overall positive rate and positive rate of each high-risk feature were calculated and obtained with 95% confidence intervals (CIs). Both unadjusted odds ratios (ORs) and adjusted ORs (AORs) of high-risk features were analyzed. Pooled effects were estimated using random-effects model meta-analyses. RESULTS: Sixty-six studies reporting 38,844 patients with thin melanoma who underwent SLNB met the inclusion criteria. The pooled positive rate of SLNB was 5.1% [95% confidence interval (CI) 4.9%-5.3%]. Features significantly predicted a positive result of SLNB were thickness≥0.8 mm [AOR 1.94 (95%CI 1.28-2.95); positive rate 7.0% (95%CI 6.0-8.0%)]; ulceration [AOR 3.09 (95%CI 1.75-5.44); positive rate 4.2% (95%CI 1.8-7.2%)]; mitosis rate >0/mm2 [AOR 1.63 (95%CI 1.13-2.36); positive rate 7.7% (95%CI 6.3-9.1%)]; microsatellites [OR 3.8 (95%CI 1.38-10.47); positive rate 16.6% (95%CI 2.4-36.6%)]; and vertical growth phase [OR 2.76 (95%CI 1.72-4.43); positive rate 8.1% (95%CI 6.3-10.1%)]. CONCLUSIONS: The overall positive rate of SLNB in thin melanoma was 5.1%. The strongest predictor for SLN positivity identified was microsatellites on unadjusted analysis and ulceration on adjusted analysis. Breslow thickness ≥0.8 mm and mitosis rate >0/mm2 both predict SLN positivity in adjusted analysis and increase the positive rate to 7.0% and 7.7%. We suggest patients with thin melanoma with the above high-risk features should be considered for giving an SLNB.

Association between melanoma thickness and clinical and demographic characteristics.

The large-scale implementation of primary and secondary skin cancer prevention strategies in recent decades has led to an increase in the diagnosis of thin melanomas and a decrease in the mean thickness of tumours diagnosed. The number of newly diagnosed thick melanomas, however, has remained stable. To investigate associations between melanoma thickness, clinical presentation and demographic and phenotypic characteristics. The study is based on a cross-sectional study of 1,459 patients with melanoma from a dermatology department at a tertiary hospital in Spain between 2000 and 2017. We analysed associations between median Breslow thickness and demographic, phenotypic, and clinical characteristics, including the method of melanoma detection. Age ≥ 70 years (regression coefficient [RC] =  1.2, 95% CI: 1.1-1.3; p  <  0.001), male sex (RC  =  0.9, 95% CI: 0.8-0.9; p  <  0.001), symptom-based detection (RC  =  1.3, 95% CI: 1.1-1.4; p  <  0.001), and a history of sunburn at the melanoma site (RC  =  0.9, 95% CI: 0.8-0.9; p  =  0.04) were all associated with thicker tumours. Melanomas on the lower extremities, by contrast, were significantly thinner (RC  =  0.9, 95% CI: 0.8-0.9; p = 0.04). Thick melanomas occur preferentially in older men and show changes such as bleeding or an increase in volume or colour. This information should be incorporated into health training and education programs to design better prevention strategies and minimize diagnostic delays.

The role of FDG-PET-CT is limited in initial staging of nodal metastasis for thin cutaneous melanoma.

INTRODUCTION: Positron emission tomography computed tomography (PET-CT) is often used to stage nodal metastases in thin cutaneous melanoma, with limited evidence. METHODS: A retrospective review of patients with cutaneous malignant melanoma treated at our institution was performed from 2005 to 2015, identifying those who received a PET-CT prior to lymphadenectomy. Biopsy features, lymph node status, and PET-CT results were collected. We calculated the overall sensitivity, specificity, accuracy, likelihood ratios, and positive predictive value of PET-CT in identifying nodal metastases. Results were stratified by initial biopsy tumor depth. RESULTS: We identified 367 cases; 95 obtained a PET-CT prior to lymphadenectomy. Overall, sensitivity and specificity of PET-CT was 34.6% and 95.4%, respectively. The positive likelihood ratio and negative likelihood ratio were 7.62 and 0.68, respectively. The accuracy was 78.2%. The positive predictive value for T3 and T4 melanomas were 100% and 81.4%, respectively. For thin melanomas, specificity and accuracy was 88.2% and 88.2%, respectively. CONCLUSIONS: PET-CT has low specificity and its use alone is not recommended for initial staging of nodal metastases in thin cutaneous malignant melanoma.

Peritumoral Immune Infiltrate as a Prognostic Biomarker in Thin Melanoma.

Thin melanomas are tumors less than 1 mm thick according to Breslow classification. Their prognosis is in most cases excellent. However, a small subset of these tumors relapses. These clinical findings emphasize the need of novel prognostic biomarkers to identify this subset of tumors. Characterization of tumor immune microenvironment (TIME) is currently investigated as a prognostic and predictive biomarker for cancer immunotherapy in several solid tumors including melanoma. Here, taking into account the limited availability of tumor tissues, by characterizing some of the characteristics of TIME such as number of infiltrating lymphocytes, HLA class I antigen and PD-L1 expression, we show that number of infiltrating CD8+ and FOXP3+ T cells as well as CD8+/FOXP3+ T cell ratio can represent a useful prognostic biomarker in thin melanoma. Although further investigations in a larger patient cohort are needed, these findings have potential clinical significance since they can be used to define subgroups of thin melanoma patients who have a worse prognosis and might need different treatment modalities.