Histologically low‐grade, yet biologically high‐grade, canine cutaneous mast cell tumours: A systematic review and meta‐analysis of individual participant data

Abstract

Low-grade canine cutaneous mast cell tumour (cMCT) with metastasis at the time of treatment is uncommonly reported, with few studies focusing on this specific clinical entity. The specific objective of this study was to systematically review the veterinary literature and perform a meta-analysis summarizing the clinical presentation, treatments reported and clinical outcomes from dogs with histologically low-grade cMCT and metastasis present at initial treatment. A total of 980 studies were screened with eight publications providing data on 121 dogs ultimately included. The most common treatments were surgery with adjuvant chemotherapy in 83/121 (69%) dogs; combined surgery, radiation and chemotherapy in 17/121 (14%) dogs; chemotherapy alone in 12/121 (10%) dogs and surgery alone in 7/121 (6%) dogs. Dogs with distant metastasis (n = 22) experienced significantly shorter survival compared with those with regional lymph node (RLN) metastasis (n = 99; median 194 vs 637 days; P < .01). Two variables were significantly associated with increased risk of death: presence of distant (vs RLN) metastasis (hazard ratio = 2.60; P < .01) and not receiving surgery as a component of treatment (hazard ratio = 3.79; P < .01). Risk of bias was judged to be low in terms of selection and performance bias but high in terms of detection and exclusion bias. In conclusion, dogs with cMCT and RLN metastasis can be expected to live significantly longer than those with distant metastasis, and surgery appears to have a role in extending survival of metastatic low-grade cMCT.

A retrospective study on prophylactic regional lymphadenectomy versus nodal observation only in the management of dogs with stage I, completely resected, low-grade cutaneous mast cell tumors

“…Nevertheless, it is the authors’ opinion that the significant uncertainty in staging work-up and the considerable variability in current practice, mainly due to the lack of prospective evidence, have led to the unstandardized management of locoregional disease. While lymphadenectomy is the current standard approach for clinically suspected or positive LNs, regardless of histological grade of the primary tumor [ 7 , 24 ], whether clinically unaffected LNs should undergo prophylactic regional lymphadenectomy when the primary cMCT is resected or whether only the primary cMCT should be resected remains a dilemma. Our results overall showed no significant differences in ST between operated dogs and those undergoing OO.…”

Review of Histological Grading Systems in Veterinary Medicine

“…The majority of Patnaik grade I MCTs are associated with an excellent prognosis and are usually cured by complete surgical excision. 53,81,106 Reports of metastasis of grade I MCTs exist, but they are rare 4,97,120 and, in view of the possible subjectivity in differentiating grade I and grade II MCTs, studies incorporating inter-pathologist agreement on grade I tumors would further clarify their prognostic significance. Patnaik grade III MCTs have been documented to be more aggressive than grade I MCTs with higher rates of local recurrence, metastasis, and tumor-related death and often requiring adjunctive therapy.…”

A retrospective study on prophylactic regional lymphadenectomy versus nodal observation only in the management of dogs with stage I, completely resected, low-grade cutaneous mast cell tumors

“…Nevertheless, the significant uncertainty in staging work-up and the considerable variability in current practice, mainly due to the lack of prospective evidence, have led to the unstandardized management of localized disease. While lymphadenectomy is the current standard approach for clinically suspected or positive LNs, regardless of histological grade of the primary tumor, 4,21,22 whether clinically unaffected LNs should undergo prophylactic regional lymphadenectomy when the primary cMCT is resected or whether only the primary cMCT should be resected remains a dilemma. Thus, the goal of this retrospective study was to assess the therapeutic role of prophylactic lymphadenectomy of pathologically uninvolved regional LNs in canine cMCTs.…”

“…Nevertheless, provided that cytologic grading may help predicting the histological grade, due to the high rate of locoregional relapse, high-grade MCTs will require lymphadenectomy in any case. [19][20][21][22] Last, even though the median follow-up time was not significantly different among groups, dogs undergoing OO were monitored for a median of days versus a median of 763 days for dogs undergoing nodal dissection. It cannot be excluded that, with a longer follow-up in operated dogs, the outcome differences may cancel out.…”