High Mitotic Rate Predicts Sentinel Lymph Node Involvement in Thin Melanomas

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.

Predictive accuracy of elevated mitotic rate on lymph node positivity and recurrence in thin melanomas

Background

Mitotic rate (MR) is considered an important prognostic factor for melanoma but is not currently used for staging because its nuanced effect is not yet well-delineated. We sought to determine if T category-specific MR is predictive of sentinel lymph node (SLN) positivity, recurrence, and melanoma-specific mortality (MSM).

Methods

A retrospective review of patients with primary cutaneous melanoma from 1994 to 2020 at a single academic center was performed. Patient demographics and tumor characteristics were recorded. MR was considered elevated for each AJCC8-defined T category if it was ≥2 mitoses/mm² for T1, ≥4 mitoses/mm² for T2, ≥6 mitoses/mm² for T3, or ≥7 mitoses/mm² for T4. Statistical analysis was performed to assess the predictive accuracy of MR on selected outcomes while controlling for ulceration.

Results

Data from 2,984 patients with complete records were analyzed. Along with Breslow thickness and ulceration, elevated MR was associated with higher risk of MSM (HR 1.816, P=0.0001). There was no difference among patients with ulcerated T1 or T2 tumors regardless of MR, but those with non-ulcerated T1 or T2 tumors and elevated MR were more likely to have positive SLNs (P<0.0001 and P=0.0043, respectively) and recurrence (P=0.0007 and P=0.0004, respectively) compared to counterparts with low MR. There were no notable differences for T3 or T4 tumors based on MR.

Conclusions

Elevated MR is associated with SLN positivity and recurrence in thin melanomas, independent of ulceration. SLN biopsy should therefore be strongly considered for patients with non-ulcerated lesions <0.8 mm thick if the MR is ≥2 mitoses/mm².

Ulceration vs Mitosis in Cutaneous Melanoma: which is Superior for Predicting Prognosis Across Clinical Stages?

Ulceration and high mitosis are considered among the major unfavorable prognostic factors in the survival of cutaneous melanoma patients. The aim of this study was to investigate the clinical significance of these parameters and to compare them to see which one is superior to predicting prognosis across all clinical stages of melanoma. A total of 1,074 melanomas were analyzed retrospectively. Tumor ulceration was found to be limited to the local stage for predicting survival, whereas, mitosis maintained its prognostic strength for predicting survival across all clinical stages. Furthermore, no survival differences were observed between ulceration and mitosis across clinical stages.

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.

Different mitotic rates are associated with different prognostic factors, relapses, and survival rates in melanoma

BACKGROUND

Mitotic rate is one of the major prognostic factors in melanoma.

OBJECTIVE

To investigate the significance of mitotic rate and possible impacts of clinicopathological factors on the course of all staged melanoma patients.

METHODS

A total number of 970 melanoma patients were analyzed. Mitotic rates were grouped for analysis as follows: 0-1, 1.1-4.9, 5-9.9, and ≥10 mitoses/mm² .

RESULTS

Melanomas with higher mitotic rates were more likely to be associated with nodular histology (P = 0.0001), higher Clark level (P = 0.0001), thick Breslow depth (P = 0.0001), ulceration (P = 0.0001), vertical growth pattern (P = 0.0001), neurotropism (P = 0.04), lymphovascular invasion (P = 0.01), de novo melanoma (P = 0.0001), absence of tumor infiltrating lymphocytes (P = 0.02), advanced stage (P = 0.0001), and relapse (P = 0.0001). The 5-year overall survival (OS) rate of all patients was 68.7%, and it decreased significantly from 87% in melanomas with 0-1 mitoses/mm² to 65.2%, 56.6%, and 50.4% in melanomas with 1.1-4.9, 5-9.9, and ≥10 mitoses/mm² , respectively (P = 0.0001). Age (P = 0.04), gender (P = 0.03), histology (P = 0.0001), Clark level (P = 0.001), T-stage (P = 0.003), ulceration (0.006), node involvement (P = 0.0001), metastasis (P = 0.005), and relapse (P = 0.0001) were correlated with OS in 0-1 mitoses/mm² melanomas, whereas lymphovascular invasion (P = 0.0001), BRAF mutation (P = 0.01), metastasis (P = 0.0001), relapse (P = 0.0001), and relapse pattern (P = 0.005) were found significant for ≥10 mitoses/mm² melanomas.

CONCLUSION

Higher tumor mitotic rates associated with known histopathological and clinical poor prognostic factors were found to be significantly independent predictors of early relapse and unfavorable survival for cutaneous melanoma patients. Moreover, different prognostic variables were found to be affecting survivals in melanoma patients with lower and higher mitosis.