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Mitotic rate not significantly associated with SLN outcomes in thin melanomas

Mitotic rate was not a significant predictor of sentinel lymph node status in thin melanomas when stratified by Breslow thickness, according to recently published study results.

Researchers reviewed a provincial tumor database to study 1,072 patients who underwent sentinel lymph node biopsy (SLNB) between 2007 and 2013 in Alberta, Canada.

Mitotic rate was a good predictor of SLN status in an analysis of all melanomas, regardless of thickness. The researchers reported that 25.4% of all SLNB cases were positive.

Only intermediate melanomas (1.01 mm-2 mm) displayed an association between mitotic rate and positive SLN status (P = .01) when stratified by Breslow thickness. There was no association with SLN status in melanomas 1 mm or smaller. Almost 9% of melanomas that underwent SLNB were positive, and they had an average Breslow depth of 0.85 mm.

“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),” the researchers wrote.

“Mitotic rate was not associated with SLN outcome in thick or thick melanomas,” the researchers concluded. “It may have predictive value in intermediate-thickness tumors, which have sufficient likelihood of nodal progression, yet are not so advanced that tumor thickness overrides other prognostic factors.

“Using current methods, this study does not support the use of mitotic rate to predict SLN positivity in thin melanomas.” – by Bruce Thiel

Disclosure: Wat reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.