Recurrence rates and clinical outcome for dogs with gradeIImast cell tumours with a lowAgNORcount and Ki67 index treated with surgery alone

Abstract

Grade II mast cell tumours (MCT) are tumours with variable biologic behaviour. Multiple factors have been associated with outcome, including proliferation markers. The purpose of this study was to determine if extent of surgical excision affects recurrence rate in dogs with grade II MCT with low proliferation activity, determined by Ki67 and argyrophilic nucleolar organising regions (AgNOR). Eighty-six dogs with cutaneous MCT were evaluated. All dogs had surgical excision of their MCT with a low Ki67 index and combined AgNORxKi67 (Ag67) values. Twenty-three (27%) dogs developed local or distant recurrence during the median follow-up time. Of these dogs, six (7%) had local recurrence, one had complete and five had incomplete histologic margins. This difference in recurrence rates between dogs with complete and incomplete histologic margins was not significant. On the basis of this study, ancillary therapy may not be necessary for patients with incompletely excised grade II MCT with low proliferation activity.

Histologic margins and the residual tumour classification scheme: Is it time to use a validated scheme in human oncology to standardise margin assessment in veterinary oncology?

“…While complete histologic excision is the goal of oncologic surgery, complete histologic excision does not preclude the possibility of local tumour recurrence. Local recurrence rates of 3% to 22% have been reported following complete histologic excision of cutaneous and subcutaneous STSs, 2% of dogs with subcutaneous MCTs, and 2% to 11% of dogs with low‐grade cutaneous MCTs, and 36% of high‐grade cutaneous MCTs . In one meta‐analysis of cutaneous and subcutaneous STSs in dogs, the overall local recurrence rate was 9.8% following complete histologic excision, defined as a HTFM >0 mm, in the 10 included studies .…”

“…[1][2][3][4][5][6] However, in some studies, an incomplete histologic excision has been arbitrarily defined as a HTFM ≤1 mm, [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] ≤2 mm 23 or ≤5 mm. 24 The assessment of histologic margins is further complicated by the common use of 'close' or 'narrow' histologic margins in veterinary oncology. 25 This term is rarely used in human oncology and the use of this term is not recommended according to a consensus paper by the American College of Veterinary Pathologists Oncology Committee on the evaluation and reporting of histologic margins in veterinary oncology.…”

“…77 The relatively low recurrence rate of incompletely excised canine cutaneous MCTs has been associated with low proliferation indices, such as Ki67, PCNA and AgNORs. 18,24 Mast cells observed at the periphery of histologic sections of resected MCTs may be associated with a local inflammatory reaction, which highlights the difficulty in differentiating between normal and neoplastic mast cells. 15,78 Logistically, local tumour recurrence may be missed because follow-up times may be inadequate in some studies.…”

Outcome of adjuvant chemotherapy with lomustine, vinblastine and chlorambucil on management of canine mast cell tumour of high to intermediate risk

“…This result is similar to findings obtained from patients presenting a similar fashion that were treated with radiotherapy or chemotherapy in the adjuvant setting (Al-Sarraf et al, 1996;Thamm et al, 2006;Cooper et al, 2009), and it is not different from the result achieved in the intermediate-risk control group (group B3) and low-risk (group C), without any divergence on DFI and OS. Systemic adjuvant treatment might be unnecessary for patients with low-tointermediate grade MCT, as they were defined in this study, even in the abscence of clean surgical margins, as also demonstrated by Smith et al (2015). The classification according to the risk of recurrence or metastasis used in this study is not ideal and an improved one is necessary for a more accurate decision-making process about the use of adjuvant therapies.…”

Small animal oncology: how to give a client a more accurate prognosis

“…AgNORs are thought to indicate the rate of proliferation so combining this count with a marker of the number of cells in the cell cycle, such as Ki-67, seems to be a rational approach. In one study, a low AgNOR x Ki-67 count was associated with a low chance of recurrence, regardless of surgical margins (Smith and others 2017). …”