Increased rate of upstaging of plantar melanomas may warrant more radical treatment: Study at a single NCI-designated Cancer Center

Background

Acral lentiginous melanoma holds the worst prognosis of all cutaneous melanomas. We aim to further detail the incidence of upstaging in plantar melanoma (PM) as well as identify factors associated with upstaging.

Methods

A retrospective analysis of medical records was performed of patients who underwent surgical intervention for non-metastatic primary PM at a single NCI-designated Comprehensive Cancer Center (January 2011-August 2023). The primary outcome was rate of upstaging, defined as an increase in the T-stage on final surgical pathology compared to biopsy. Clinical and pathologic staging were determined by the AJCC 8th edition. Statistical analysis included Pearson’s Chi-squared test, Fisher’s exact test, Wilcoxon rank sum test, and Kruskal-Wallis rank sum test.

Results

Forty-nine patients were identified, with an average age of 65 years (51 % male). Majority self-identified as Caucasian (55 %). Initial biopsy techniques were shave (49 %), punch (34 %) and excisional (17 %). Twenty-four patients (50 %) demonstrated upstaging. Seventy-seven percent (n = 10) of patients with clinical Tis were upstaged. Eight patients required reoperation due to upstaging, with 6 having melanoma in situ on biopsy. On multivariable logistic regression, patients with clinical Tis-T1 were more likely to be upstaged compared to T2-T3 (OR 8.75, p < 0.041). Type of biopsy, lesion size < 15 mm and positive deep margins on biopsy were not associated with risk of upstaging.

Conclusions

Our findings suggest a high incidence of upstaging of PM with no identifiable factors associated with upstaging. Patients with clinical Tis or T1 PM should undergo resection with wider margins and be strongly considered for sentinel lymph node biopsy at time of index operation.

Synopsis

In this large cohort of patients with non-metastatic primary plantar melanoma, half of the cohort was upstaged following resection. The risk was higher in patients diagnosed with Tis or T1 on biopsy compared to T2-T3. Biopsy type, lesion size < 15 mm and positive deep biopsy margins were not associated with upstaging. More radical treatment of plantar melanomas may be warranted.