Abstract

Background:
Malignant melanoma of the canine metacarpal pad presents a surgical challenge because removal of tumor-bearing pad tissue must be balanced with reconstruction of a durable weight-bearing surface. Although second-digit pad transfer has been described for selected metacarpal pad defects, reconstruction completed with the second digit alone after total metacarpal pad excision for canine metacarpal pad malignant melanoma, while preserving the fifth digit, has not been documented to the authors’ knowledge.

Case Description:
A 12-year-old male Miniature Schnauzer was referred for a bleeding mass contiguous with the left forelimb metacarpal pad. Punch biopsy confirmed malignant melanoma, and cytology of the left superficial cervical and axillary lymph nodes suggested reactive lymphadenopathy. Twelve days after initial examination, the tumor-bearing metacarpal pad was excised en bloc, the left superficial cervical lymph node and a pigmented right upper lip lesion were excised, and the metacarpal pad defect was reconstructed using a phalangeal fillet technique. Reconstruction using both the second and fifth digits had been anticipated preoperatively, but temporary transposition of the filleted second digit suggested adequate central weight-bearing coverage and contour. Therefore, reconstruction was completed with the second digit alone and the fifth digit was preserved. Histopathology confirmed malignant melanoma of the metacarpal pad, with no neoplastic cells identified at the surgical margins, and no neoplastic lesion in the left superficial cervical lymph node. The right upper lip lesion was also malignant melanoma; subsequent wider excision and right mandibular lymph node biopsy revealed no residual or nodal neoplastic lesion. Retrospective two-dimensional planimetry showed that the contralateral second digital pad area was 26.9% of the contralateral metacarpal pad area. Postoperatively, localized incomplete wound healing occurred without infection. Weight-bearing was possible by postoperative day 14, and no visually apparent left forelimb lameness was observed during ordinary in-hospital walking approximately 4 weeks after surgery.

Conclusion:
This case suggests that, in selected dogs, short-term weight-bearing reconstruction after total metacarpal pad excision for malignant melanoma may be achieved using the second digit alone while preserving the fifth digit.

Key words: Digital pad transposition; Malignant melanoma; Metacarpal pad; Phalangeal fillet technique; Weightbearing reconstruction.