Evaluation of a modified proportional margin approach for complete surgical excision of canine cutaneous mast cell tumours and its association with clinical outcome

Abstract

Canine cutaneous mast cell tumours (MCTs) represent a common neoplasm in veterinary practice. Several reported techniques are available to guide surgical excision.Our study examined one hundred cutaneous MCTs that were excised surgically using a modified proportional margin approach. A 2 cm lateral margin upper limit was applied for any tumour diameter that exceeded this size with a deep surgical margin of one fascial plane applied. A retrospective, cross-sectional study with follow-up was used to determine the clinical utility of this excision technique. Associations between explanatory variables of tumour size and grade were compared with outcomes of complete excision and size of histologic tumour-free margins (HTFM) using the appropriate Pearson's χ 2 and Fisher's exact tests. Follow-up data evaluated tumour recurrence and patient survival. Ninety-five percent of MCTs (95/100) were completely excised. No significant association in the achievement of complete excision between low-and high-grade MCTs (P = .48) was noted. Tumour size was not associated with the rate of complete excision (P = .06). Tumour grade and size did not influence the size of the HTFM (P = .94 and P = .14, respectively). Overall, a recurrence rate of 3% (3/100 tumours) and de novo MCT development rate of 7.7%(5/65 dogs) was noted, with median follow-up period of 593 days (range 180-1460 days). Post-operative metastases were seen in 4.6% of dogs (3/65). Therefore, a modified proportional margin approach with 2 cm lateral margin upper limit is a suitable technique to guide surgical excision of canine cutaneous MCTs.

Diagnosis, Prognosis and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors

“…The concept initially consisted of using a lateral margin proportional to the largest tumor diameter, for tumors below 4 cm, and a fixed margin of 4 cm for tumors above this diameter, maintaining a deep margin of at least one fascial plane [ 150 ]. Later, the concept was adapted, with a 2 cm lateral and a deep safety margin of a fascial plane being recommended for grade 1 or 2 tumors, and up to 4 cm in diameter, providing effective local control of the disease [ 151 , 152 , 153 , 154 ], with a recurrence rate of 0–4% [ 82 , 150 , 155 ]. In cases of high-grade (or grade 3) MCTs, there is a high recurrence rate (36%) regardless of the surgical margins used, as observed in the study by Donelly et al [ 156 ].…”

Tigilanol Tiglate-Mediated Margins: A Comparison With Surgical Margins in Successful Treatment of Canine Mast Cell Tumours

“…For our comparison of TT-mediated margins with surgical margins that would have been theoretically applied to treatment of the same tumour, we selected (i) aggressive 3 cm margins because they are widely used in general veterinary practise ( 11 – 17 , 19 , 22 , 23 ) and (ii) the more recently developed modified proportional margins method with a 2 cm limit ( 20 ) as a more conservative approach, which causes less local tissue disruption and which is gaining traction in veterinary practise. Our results suggest that there would have been significantly less local tissue disruption associated with TT than with these surgical approaches for most dogs in this study, especially for MCTs <2 cm 3 in volume, which comprised 80% of the tumours in the study population.…”

“…For comparisons with surgical margins for MCTs, we selected 3 cm margins as an example of the commonly used aggressive wide surgical approach (11)(12)(13)(14)(15)(16)(17)(18)(19), together with the recently developed modified proportional margin strategy with a 2 cm upper limit (20). In calculating the theoretical proportional surgical margins, we followed the methods described by Saunders et al, (20) and used the largest diameter of each individual tumour at the time of treatment.…”

Intratumoural Treatment of 18 Cytologically Diagnosed Canine High-Grade Mast Cell Tumours With Tigilanol Tiglate

“…For dogs classified as not-CR after 28 days, the protocol was repeated with a second intratumoural TT injection. After the Day 84 treatment response assessment, longterm follow-ups were conducted at 6, 12, 18, and 24 months to assess presence or absence of a treatment site recurrence (TSR) with local recurrence defined as development of a cytologically confirmed MCT at or within 2 cm of the original TT treatment site (38)(39)(40). In the event of a TSR, patients involved in the Australian studies were reassessed, and if eligibility criteria were met, a repeat treatment cycle was administered.…”