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

Area of Science:

• Oncology
• Dermatology
• Pathology

Background:

• Mitotic rate (MR) is a prognostic factor in melanoma, but its role in staging is not fully understood.
• The nuanced effect of MR on melanoma progression requires further delineation.
• Current melanoma staging does not incorporate MR due to its complex impact.

Purpose of the Study:

• To determine if T category-specific MR predicts sentinel lymph node (SLN) positivity.
• To assess the predictive value of MR for melanoma recurrence.
• To evaluate the association of MR with melanoma-specific mortality (MSM).

Main Methods:

• Retrospective review of 2,984 primary cutaneous melanoma patients (1994-2020).
• Defined elevated MR thresholds for AJCC8 T categories (T1-T4).
• Statistical analysis controlled for ulceration to assess MR's predictive accuracy for SLN positivity, recurrence, and MSM.

Main Results:

• Elevated MR, along with Breslow thickness and ulceration, correlated with increased MSM risk (HR 1.816, P=0.0001).
• In non-ulcerated T1/T2 melanomas, elevated MR predicted higher rates of SLN positivity and recurrence.
• No significant differences in outcomes were observed for T3/T4 tumors based on MR.

Conclusions:

• Elevated MR is linked to SLN positivity and recurrence in thin melanomas, irrespective of ulceration.
• SLN biopsy is recommended for non-ulcerated melanomas <0.8mm with elevated MR (≥2 mitoses/mm²).
• MR may refine risk stratification for specific melanoma subtypes.