Introduction

Melanomas arising from the foot pad are a rare clinical entity in dogs. The biologic behavior of foot pad malignant melanoma is not well understood, and these tumors are infrequently described. The primary objective of this study was to evaluate the clinical characteristics of primary canine foot pad melanoma in a larger cohort of patients.

Methods

Eligible cases were solicited from the ACVIM Oncology listserv for retrospective review. Included dogs had a cytologic and/or histologic diagnosis of foot pad melanoma evaluated by a board-certified clinical or anatomic pathologist. Dogs with cutaneous, oral, digital, subungual, or interdigital melanomas were excluded. Complete medical records and follow-up information for at least 8 weeks were required for inclusion.

Results

Twenty dogs from eleven institutions met the inclusion criteria. Most patients (19/20) had surgical resection with (5/19) or without (14/19) preceding pre-operative incisional biopsy. One patient had incisional biopsy alone. At diagnosis, regional lymph node metastasis was observed in four dogs. Eleven dogs received various adjuvant therapies including chemotherapy, radiation therapy, and/or the Oncept melanoma vaccine following surgery. Seven dogs developed subsequent regional and/or distant metastasis. The progression-free interval (PFI) was 101 days (range, 20–960 days). The median survival time (MST) was 240 days (range, 25–479 days). For dogs receiving adjuvant therapy, the MST was 159 days (range, 25–387 days).

Conclusion

Canine foot pad melanoma is a rare neoplasm that can exhibit an aggressive behavior. Adjuvant treatment was not shown to prolong survival. However, further studies are warranted to continue to investigate outcome and significant prognostic factors.

Funding Information

N/A