Scar revision for incompletely or narrowly excised cutaneous mast cell tumors in dogs.

Objective: Describe clinical features and outcomes of dogs undergoing scar revision for incompletely or narrowly excised cutaneous mast cell tumors without gross disease.

Animals: 52 dogs undergoing 54 scar revisions.

Procedures: Retrospective record review with information collected on signalment, tumor type/location, pre-surgical diagnostics, surgical and pathologic findings for the first excision and scar revision surgeries, and follow-up. Descriptive statistics were generated.

Results: Prior to initial excision, cytology was performed on 38.9% (21/54) of tumors and the initial surgery report rarely described surgical resection margins [14.6% (7/48) of surgeries]. Residual tumor was identified pathologically in 29.6% (16/54) of scars. Local recurrence following scar revision occurred in 3.7% (2/54) of all scars [median follow-up 881.5 d (range: 0 to 3317 d)]; both scars had either complete excision of residual mast cell tumor or no evidence of mast cell tumor on scar revision and neither dog received radiation therapy.

Conclusions: Identification of residual disease was uncommon, and local recurrence was less common than previously reported for incomplete/narrow mast cell tumor excision.

Clinical Relevance: Scar revision of unplanned primary excisions appears to yield a high likelihood of durable tumor remission in patients. First opinion practitioners are encouraged to avoid unplanned excisions by informing the surgical plan with cytology of the primary tumor and detailing surgical margin excision which may facilitate revision, if necessary.