Mitotic rate as an important prognostic factor in cutaneous malignant melanoma

BACKGROUND

Recently, the quantification of mitoses in cutaneous melanoma has been discharged from the main prognostic variables of the TNM classification.

OBJECTIVE

To investigate the prognostic value of the presence of mitoses in primary cutaneous melanoma and to establish the number of mitoses per mm2 that may have prognostic significance.

METHODS

A retrospective observational study was performed on 141 patients treated for cutaneous melanoma, who were assessed by the same pathologist, and who had a minimum follow-up of 2 years. Clinical, epidemiological, histopathological and follow-up variables were gathered and compared with the number of mitoses to distinguish the significance of differences by means of univariate, multivariate, and survival analyses.

RESULTS

The cut-off level related to a better sensitivity and specificity was 1.50 mitoses per mm2. The presence of two or more mitoses/mm2 showed a better relationship with prognostic variables and both the overall and disease-free survival than the presence of 1 or more mitoses/mm2. This happens especially in melanomas thicker than 0.8 mm and it could affect the staging in cases with Breslow between 1 and 2 mm.

CONCLUSIONS

A mitotic rate of two or more mitoses per mm2 in cutaneous melanoma should be considered as a more accurate prognostic factor than one or more mitoses per mm2, particularly in tumors equal or greater than 0.8 mm in thickness.

Tumor Mitotic Rate and Association with Recurrence in Sentinel Lymph Node Negative Stage II Melanoma Patients

Tumor mitotic rate (TMR) is a known prognostic variable in thin melanoma patients. Its significance in stage II melanoma patients is yet to be demonstrated. Retrospective analysis of a prospective melanoma database from 9/1997 to 7/2015 was performed. All stage II melanoma, with documented TMR, and six months of follow-up were included. We evaluated the association of clinicopathologic variables, TMR, as a continuous and categorical variable with recurrence-free survival (RFS) and overall survival (OS) using Cox proportional hazards modeling. We used a statistical model, X-tile, to develop optimal categorizations of TMR. A total of 265 patient characteristics are included in this study. Recurrences occurred in 82 (30.9%) patients, including 5 local, 41 regional, and 36 distant patients. In multivariate model, ulceration, Breslow, and continuous TMR were associated with worse RFS\OS. Continuous TMR demonstrated worse RFS (hazards ratio [HR] 1.02 (1.00–1.05)) and OS (HR 1.02 (1.00–1.04)), whereas dichotomized TMR (≥1 vs <1) was not significant. TMR >10.4 mitoses/mm2 has a 5-year RFS\OS of 27.2 and 44.3 per cent, respectively, compared with 57.4 and 71.4 per cent, respectively, for TMR <3.2 mitoses/mm2. Continuous TMR predicts incidence of recurrence in stage II melanoma. We propose a new categorization method developed by statistical modeling for optimal stratification that may guide surveillance for this disparate patient population.

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.