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Melanoma

E334: Surgical management of plantar melanoma: a retrospective review analyzing frequency of upstaging at a single NCI-designated cancer institution.

Introduction: Acral lentiginous melanoma comprises a small percentage of total melanoma diagnoses and holds the worst prognosis of all cutaneous melanomas. We aim to further detail the incidence of upstaging in plantar melanoma as well as identify factors associated with upstaging.

Methods: A retrospective analysis of medical records was performed of patients who underwent surgical intervention for cutaneous plantar melanoma at a single NCI-designated Comprehensive Cancer Center from January 2011 through August 2023. Included patients were diagnosed with non-metastatic primary melanoma on the plantar surface of the foot. The primary outcome was rate of upstaging, defined as an increase in the T-stage on final surgical pathology. Clinical staging was 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: 49 patients were included, with an average age of 65 years. 51% were male. Majority self-identified as Caucasian (55%), with 10% identifying as Black and 10% as Asian. Most patients underwent shave biopsy (48%), followed by punch (34%) and excisional (18%). The most common T-stage on initial biopsy was T1 (n=15), followed by T2 (n=14) and Tis (n=13). The most common final pathology was T1 (n=14) and T2 (n=14). A total of 23 patients (48%) demonstrated an increase in T-stage from initial biopsy to final pathology. One patient was excluded from upstaging analysis given unobtainable staging on biopsy. Of those that were upstaged, initial biopsy types were excisional (9.5%), punch (43%), and shave (48%). For patients initially diagnosed with melanoma in situ, 10 (77%) were upstaged. 7 patients required re-excision or sentinel lymph node biopsy based on final pathology; 6 of these were upstaged from Tis initially. Nine patients were upstaged by more than one T-stage. Type of biopsy, lesion size and positive deep margins were not associated with increased risk of upstaging.

Conclusions: Our findings suggest a high incidence of upstaging of plantar melanoma. Nearly half of the cohort demonstrated some degree of upstaging, particularly for those diagnosed with melanoma in situ on biopsy, with no identifiable factors associated with upstaging. This knowledge may be used to promote shared decision-making regarding a more aggressive approach to surgical intervention and course of treatment, but further investigation is required.

Learning Objectives:

  • identify patients at risk for upstaging in plantar melanoma.
  • critically assess the current guidelines for surgical margins for patients with plantar melanoma.
  • propose shared decision making amongst surgeons and patients.