J. E. Miller1, S. A. Debolle1, T. N. Ballard2, A. B. Durham3, J. H. Kozlow2 1University Of Michigan,Medical School,Ann Arbor, MI, USA 2University Of Michigan,Department Of Surgery,Ann Arbor, MI, USA 3University Of Michigan,Department Of Dermatology,Ann Arbor, MI, USA
Introduction: The plantar surface of the foot is unique due to its ridged epidermis and ability to undergo hyperkeratosis. It is unclear if melanomas arising on the plantar surface of the foot behave clinically similar to melanomas in other areas of non-glabrous skin, making clinical decision-making and treatment more challenging. The two specific aims of this study were to determine the accuracy of the Breslow depth of the initial biopsy and to determine the incidence of positive microscopic margins following an intended curative excision.
Methods: In this retrospective study, we reviewed the charts of 103 patients with plantar foot melanoma treated at the University of Michigan from 1997 to 2015. The Breslow depth from the initial biopsy pathology report was compared to the Breslow depth in the final pathology report following either repeat biopsy or definitive surgical excision. These results were compared both in absolute Breslow depth and for changes in Tumor staging. We evaluated the microscopic margin status on the pathology report and used published guidelines to determine if appropriate surgical margins were taken in the intended curative resection.
Results: A total of 46 patients (45.5%) had an increase in Breslow depth compared to their initial biopsy, with 34 (33.7%) having an increase substantial enough to change their tumor staging. A total of 16 patients (15.5%) had positive microscopic margins following an intended curative excision. Patients with stage T3 and T4 tumors had the highest incidence of positive microscopic margins, with 21.4% and 30.0%, respectively, requiring a re-excision. Of the 70 patients treated with surgical margins in accordance with NCCN guidelines, 12 (17.1%) had positive microscopic margins, whereas only 1 (6.3%) of the 16 patients treated with margins larger than guideline recommendations had positive microscopic margins.
Conclusion: The surgical management of plantar foot melanoma depends on the Breslow depth of the tumor. Current practices often use the initial biopsy pathology report to determine Breslow depth of the tumor, however our findings show that these values are often incorrect and frequently under-stage the actual tumor depth. Additionally, clinicians should be aware of the high rate of positive microscopic margins in this area of the body, even when standard guidelines are followed. This information will allow for improved informed shared decision making with patients and will affect the timing of reconstructive procedures.
