Prognostic factors for survival of dogs with inguinal and perineal mast cell tumors treated surgically with or without adjunctive treatment: 68 cases (1994-2002)

OBJECTIVE: To determine the prognostic factors for survival and tumor recurrence in dogs with cutaneous mast cell tumors (MCTs) in the perineal and inguinal regions treated surgically with or without adjunctive radiation therapy, chemotherapy, or both. DESIGN: Retrospective study. ANIMALS: 68 dogs. PROCEDURE: Medical records of dogs with histologically confirmed MCTs in the perineal region, inguinal region, or both treated surgically with or without adjunctive radiation therapy, chemotherapy, or both were reviewed. RESULTS: Mean tumor-free interval was 1,635 days (median not reached), and 1- and 2-year tumor-free rates were 79% and 71%, respectively. Median survival time was 1,111 days (mean, 1,223 days), and 1- and 2-year survival rates were 79% and 61%, respectively. Factors that negatively influenced survival time were age at diagnosis, tumor recurrence, and treatment with lomustine. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that dogs with MCTs in the inguinal and perineal regions, if appropriately treated, may have survival times and tumor-free intervals similar to dogs with MCTs in other locations.     

Evaluation of prognostic factors associated with outcome in dogs with multiple cutaneous mast cell tumors treated with surgery with and without adjuvant treatment: 54 cases (1998-2004)

OBJECTIVE: To evaluate prognostic factors associated with outcome of dogs with multiple cutaneous mast cell tumors (MCTs) treated with surgery with or without adjuvant treatment. DESIGN: Retrospective case series. ANIMALS: 54 dogs with a minimum of 2 simultaneous, histologically confirmed cutaneous MCTs that had been excised and had adequate staging and follow-up data. PROCEDURE: Medical records from 1998 to 2004 were examined. Outcome was assessed with the Kaplan-Meier product-limit method and log-rank analysis. Prognostic factors evaluated included signalment; number, histologic grade, location, size, local recurrence, and de novo development of MCTs; quality of surgical margins; clinical signs at the time of diagnosis; and use of adjuvant treatment. RESULTS: Medical records of 54 dogs with 153 tumors were included. Median follow-up time was 658 days. Median disease-free interval (1,917 days; range, 11 to 1,917 days) and median survival time (1,917 days; range, 14 to 1,917 days) were not yet reached. The 1- year and 2- to 5-year survival rates were 87% and 85%, respectively. The overall rate of metastasis was 15%. Factors that negatively influenced survival time in the univariate analysis included incomplete excision, local recurrence, size > 3 cm, clinical signs at the time of diagnosis, and use of adjuvant treatment. Presence of clinical signs at the time of diagnosis was the only negative prognostic factor for disease-free interval detected in the multivariate analysis. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that multiple cutaneous MCTs in dogs are associated with a low rate of metastasis and a good prognosis for long-term survival with adequate excision of all MCTs.     

Evaluation of a two-centimeter lateral surgical margin for excision of grade I and grade II cutaneous mast cell tumors in dogs

OBJECTIVE: To evaluate completeness of excision and clinical outcome in dogs with cutaneous mast cell tumors (MCTs) excised with a lateral margin of 2 cm and a deep margin of 1 fascial plane. DESIGN: Prospective study. ANIMALS: 16 client-owned dogs with 1 or more cutaneous MCTs. PROCEDURE: Excision of MCTs was performed with a 2-cm lateral margin and a deep margin of 1 fascial plane. Histologic tumor grading was performed; surgical margins were categorized as complete or incomplete. Follow-up information was obtained via repeat examination of the dogs by veterinarians or client-completed questionnaires. RESULTS: 4 grade I and 19 grade II cutaneous MCTs were evaluated. Overall, 21 (91%) MCTs were completely excised; 2 grade II tumors had foci of mast cells at the 2-cm margin. Two dogs received adjunctive treatments following surgery. Follow-up information was available for all dogs (median follow-up period, 379 days; range, 51 to 538 days); no local recurrence was detected during this time. De novo MCTs were detected in 3 of 16 dogs at 37, 54, and 154 days after surgery. Via Kaplan-Meier analysis, median survival time and disease-free interval were both > 538 days (medians not yet reached). No prognostic variables were identified. CONCLUSIONS AND CLINICAL RELEVANCE: Excision with a 2-cm lateral margin and a deep margin of 1 fascial plane may result in satisfactory excision of grades I and II MCTs in dogs, with recurrence rates similar to those reported previously. Use of these margins may minimize complications associated with larger local tumor resection.     

Recurrence rate, clinical outcome, and cellular proliferation indices as prognostic indicators after incomplete surgical excision of cutaneous grade II mast cell tumors: 28 dogs (1994-2002)

The objectives of this study were to determine local recurrence rate, clinical outcome, and prognostic value of the number of argyrophylic nucleolar organizer regions (AgNORs), presence of proliferating cell nuclear antigen (PCNA), and number of Ki-67-positive nuclei after incomplete surgical excision of canine cutaneous grade II mast cell tumors (MCTs). This retrospective study included 30 MCTs in 28 dogs. Medical records were examined and follow-up information was obtained from owners and referring veterinarians. Only cases in which excision was incomplete and no anvcillary therapy (other than prednisone) for MCT was given were included. Paraffin-embedded tumor tissues were retrieved for AgNORs, PCNA, and Ki-67 staining. Median follow-up time was 811.5 days. Seven (23.3%) tumors recurred locally. Median time to local recurrence was not reached with a mean of 1,713 days. The estimated proportions of tumors that recurred locally at 1, 2, and 5 years were 17.3, 22.1, and 33.3%, respectively. Eleven (39.3%) dogs developed MCTs at other cutaneous locations. Median progression-free survival was 1,044 days. Median overall survival was 1,426 days. The combination of Ki-67 and PCNA scores was prognostic for local recurrence (P = .03) and development of local recurrence was prognostic for decreased overall survival (P = .04). Results suggest that a minority of incompletely excised MCTs recur. Therefore, ancillary local therapies may not always be necessary. However, local recurrence can negatively affect survival of the affected dogs. Cellular proliferation indices may indicate the likelihood of MCT recurrence after incomplete excision.     

The use of KIT and tryptase expression patterns as prognostic tools for canine cutaneous mast cell tumors

Cutaneous mast cell tumors (MCTs) are one of the most common tumors in dogs. Currently, prognostic and therapeutic determinations for MCTs are primarily based on the histologic grade of the tumor, but a vast majority of MCTs are of an intermediate grade, and the prognostic relevance is highly questioned. A more detailed prognostic evaluation, especially of grade 2 canine MCTs, is greatly needed. To evaluate the prognostic significance of KIT and tryptase expression patterns in canine cutaneous MCTs, we studied 100 cutaneous MCTs from 100 dogs that had been treated with surgery only. The total survival and disease-free survival time and the time to local or distant recurrence of MCTs were recorded for all dogs. Using immunohistochemistry, 98 of these MCTs were stained with anti-KIT and antitryptase antibodies. Three KIT- and three tryptase-staining patterns were identified. The KIT-staining patterns were identified as 1) membrane-associated staining, 2) focal to stippled cytoplasmic staining with decreased membrane-associated staining, and 3) diffuse cytoplasmic staining. The tryptase-staining patterns were identified as 1) diffuse cytoplasmic staining, 2) stippled cytoplasmic staining, and 3) little to no cytoplasmic staining. Based on univariate and multivariate survival analysis, increased cytoplasmic KIT staining was significantly associated with an increased rate of local recurrence and a decreased survival rate. The tryptase-staining patterns were not significantly associated with any survival parameter. On the basis of these results, we propose a new prognostic classification of canine cutaneous MCTs, according to their KIT-staining pattern, that can be used for the routine prognostic evaluation of canine cutaneous MCTs.     

Proposal of a 2-tier histologic grading system for canine cutaneous mast cell tumors to more accurately predict biological behavior

Currently, prognostic and therapeutic determinations for canine cutaneous mast cell tumors (MCTs) are primarily based on histologic grade. However, the use of different grading systems by veterinary pathologists and institutional modifications make the prognostic value of histologic grading highly questionable. To evaluate the consistency of microscopic grading among veterinary pathologists and the prognostic significance of the Patnaik grading system, 95 cutaneous MCTs from 95 dogs were graded in a blinded study by 28 veterinary pathologists from 16 institutions. Concordance among veterinary pathologists was 75% for the diagnosis of grade 3 MCTs and less than 64% for the diagnosis of grade 1 and 2 MCTs. To improve concordance among pathologists and to provide better prognostic significance, a 2-tier histologic grading system was devised. The diagnosis of high-grade MCTs is based on the presence of any one of the following criteria: at least 7 mitotic figures in 10 high-power fields (hpf); at least 3 multinucleated (3 or more nuclei) cells in 10 hpf; at least 3 bizarre nuclei in 10 hpf; karyomegaly (ie, nuclear diameters of at least 10% of neoplastic cells vary by at least two-fold). Fields with the highest mitotic activity or with the highest degree of anisokaryosis were selected to assess the different parameters. According to the novel grading system, high-grade MCTs were significantly associated with shorter time to metastasis or new tumor development, and with shorter survival time. The median survival time was less than 4 months for high-grade MCTs but more than 2 years for low-grade MCTs.     

Canine mast cell tumors: correlation of apoptosis and proliferation markers with prognosis

The Patnaik histologic grading system is commonly used to predict the behavior of cutaneous mast cell tumors (MCTs) in dogs, but it is less useful for grade 2 MCTs because they exhibit considerable variation in biological behavior. In this retrospective study, immunohistochemical staining for Ki-67, proliferating cell nuclear antigen (PCNA), and survivin and a standardized argyrophilic staining of nucleolar organizer regions (AgNOR) protocol were performed on 121 archived paraffin-embedded specimens of canine cutaneous MCTs, for which clinical follow-up data were available. Cox regression models indicated that the Ki-67 score (hazard ratio, 1.92; P < .001) and mean AgNOR score (hazard ratio, 2.57; P < .001) were significantly associated with Patnaik grade and survival time. A binary Ki-67 variable (cutoff point Ki-67 score = 1.8) was a significant predictor of survival for dogs with grade 2 MCTs. The estimated 1-, 2-, and 3-year survival probabilities for dogs with grade 2 MCTs and Ki-67 scores less than 1.8 were 0.92, 0.86, and 0.77, respectively (SEs, 0.08, 0.14, and 0.23, respectively; median not estimable). The corresponding survival probabilities for dogs with grade 2 MCTs and Ki-67 scores higher than 1.8 were 0.43, 0.21, and 0.21, respectively (SEs, 0.19, 0.18, and 0.18, respectively; median survival time, 395 days). No significant association was identified between survival and survivin score or PCNA score. This study shows that both mean AgNOR score and Ki-67 score are prognostic markers for canine MCTs. The Ki-67 score can be used to divide Patnaik grade 2 MCTs into 2 groups with markedly different expected survival times.     

Mitotic index is predictive for survival for canine cutaneous mast cell tumors

Mitotic index (MI) is an indirect measure of cell proliferation that has been demonstrated to be a strong predictor of outcome for several human and canine cancers. The purpose of this study was to evaluate the utility of MI as a predictor of biologic behavior and survival in dogs with cutaneous mast cell tumors (MCTs). Medical records from 148 dogs with histologically confirmed MCTs were reviewed. Information regarding tumor grade, local recurrence, metastatic disease, date of death/last follow-up, and outcome was obtained. The region of the tumor with the highest overall mitotic activity was chosen for evaluation, and the MI value was defined as the number of mitotic figures/10 high-power fields (400x, 2.7 mm(2)). A Cox proportional hazards regression model was used to compare MI with survival data. A Mann-Whitney test was used to compare MI on the basis of the development of local recurrence and metastatic disease. The MI correlated directly with tumor grade (P < .0001). The median survival time for dogs with an MI < or =5 was significantly longer (70 months) than for those with an MI >5 (2 months), regardless of grade (P < .001). For grade II tumors with an MI < or =5, the median survival time (MST) was 70 months, compared with 5 months for those with an MI >5 (P < .001). For grade III tumors with an MI < or =5, the MST was not reached, compared with <2 months for those with an MI >5 (P < .001). In conclusion, MI is a strong predictor of overall survival for dogs with cutaneous MCTs and should be included as a prognostic indicator when determining therapeutic options.     

Principles of treatment for mast cell tumors

Mast cell tumors (MCT) are the most common malignant cutaneous tumors that occur in dogs. They are most commonly found on the trunk, accounting for approximately 50% to 60% of all sites. MCTs associated with the limbs account for approximately 25% of all sites. Cutaneous MCTs have a wide variety of clinical appearances. Histologic grade is the most consistent prognostic factor available for dogs. MCTs located at 'nail bed' (subungual), inguinal/preputial area, and any mucocutaneous area like perineum or oral cavity carry a guarded prognosis and tend to metastasize. MCTs usually exfoliate well and are cytologically distinct. The extent of staging procedures following fine-needle aspirate cytologic diagnosis is based on the presence or absence of negative prognostic indicators. Surgery is the treatment of choice for solitary MCTs with no evidence of metastasis. Reponses rates to chemotherapy, (partial response) as high as 78% have been reported, and preliminary evidence suggests that multiagent (prednisone and vinblastine) protocols may confer a higher response rate than single-agent therapy. MCTs are the second most common cutaneous tumor in the cat. There are two distinct forms of cutaneous MCTs in the cat. The more common form is the mastocytic form, and the less common is the histiocytic form. Unlike in the dog, the head and neck are the most common sites for MCTs in the cat followed by the trunk and limbs. Cats with disseminated forms of MCT often present with systemic signs of illness, which include depression, anorexia, weight loss, and vomiting. The diagnosis and staging of MCTs in cats is similar to that in the dog. As with dogs with cutaneous MCTs, surgery is the treatment of choice. Little is known about the effectiveness of adjunctive chemotherapy options for cutaneous MCTs. Adjunctive chemotherapy does not appear to increase survival times.     

Impact of tumour depth, tumour location and multiple synchronous masses on the prognosis of canine cutaneous mast cell tumours

The goal of this study was to determine the significance of tumour depth, tumour location and multiple synchronous tumour masses for the prognostic evaluation of canine cutaneous mast cell tumours (MCTs). The study population consisted of 100 formalin-fixed, paraffin-embedded cutaneous MCTs that had been surgically removed from 100 dogs and submitted to the Diagnostic Center of Population and Animal Health at Michigan State University between 1998 and 2001. None of the dogs had received chemotherapy or radiation therapy. For each case the following data were obtained from the referring veterinarians: sex, breed, weight, age at diagnosis, diagnostics performed, adjunct medications given at the time of surgery, tumour location, number of tumour masses, tumour recurrence (development of MCTs at the surgical site), development of additional MCTs at distant sites (outside the surgical margins), tumour duration before removal, survival time and cause of death, if applicable. Tumour depth was determined through microscopic evaluation of 5 microm sections stained with haematoxylin and eosin. Based on univariable and multivariable survival analysis, dogs with multiple synchronous cutaneous MCTs at the time of diagnosis have a worse prognosis compared with dogs with single tumours. Additional treatment beyond surgical excision alone should be considered for these animals. Older dogs and Boxers with cutaneous MCTs were at higher risk to develop additional MCTs at distant sites (outside the surgical margins), and older and male dogs with cutaneous MCTs had significantly shorter survival times. Univariable analysis also determined that dogs with cutaneous MCTs located on the head and neck had an increased risk of additional MCT development at distant sites and that sterilized dogs with cutaneous MCTs had shorter survival times. However, these findings were not confirmed by multivariable analysis. Tumour depth was of no prognostic significance for dogs with cutaneous MCTs.     

Evaluation of prognostic indicators in dogs with multiple,simultaneously occurring cutaneous mast cell tumours: 63 cases

Sixty‐three dogs with multiple contemporaneous cutaneous mast cell tumours (MCTs) were identified. The aim of this study was to determine the significance of breed, concurrent dermatological condition; number of cutaneous MCTs, size, location, histological grade and mitotic index; completeness of excision (complete, close or incomplete); local recurrence, metastasis and adjuvant therapy for the prognostic evaluation of dogs with a unique disease presentation of multiple, simultaneously occurring cutaneous MCTs. On the basis of multivariable survival analysis, dogs with one recorded grade 3 MCT had shorter progression‐free survival (PFS) times (18.7 versus 2.2 months) and median survival times (MSTs) (24 versus 3 months). Dogs treated with adjuvant vinblastine/lomustine had a 16 times increased risk of dying. MSTs were found to be significantly longer in dogs with one recorded MCT on an extremity. For all dogs, the PFS (range 14–1835 days) and MSTs (range 28–1835 days) were not reached.     

Canine subcutaneous mast cell tumor: characterization and prognostic indices

Histologic grading schemes for canine cutaneous mast cell tumors (MCTs) were not developed for subcutaneous MCTs. Despite this, subcutaneous MCTs are currently categorized by many as grade II or higher. The aim of this investigation was to assess the pathology and clinical outcome for subcutaneous MCTs to provide a more accurate prognosis. Information on clinical outcome for 306 dogs was obtained from veterinarians and correlated with histologic features. Mean and median follow-up was 842 and 891 days, respectively (range, 3-2,305 days). Only 27 (9%) were confirmed as mast cell-related deaths. Metastasis occurred in 13 (4%), and 24 (8%) had local reoccurrence, even though 171 (56%) cases had incomplete surgical margins. Median survival time was not reached, and the estimated 6-month, 1-, 2-, and 5-year survival probabilities were 95%, 93%, 92%, and 86%, respectively. Dogs were euthanized or died as a result of local tumor reoccurrence, additional MCT development distant to the surgical site, or metastasis. Decreased survival time was linked to mitotic index (number of mitotic figures per 10 high-power fields), infiltrative growth pattern, and presence of multinucleation. Both univariable and multivariable analysis showed mitotic index to be strongly predictive of survival, local reoccurrence, and metastasis. The results of the study indicate that the majority of subcutaneous MCTs have a favorable prognosis, with extended survival times and low rates of reoccurrence and metastasis.     

Immunohistochemical detection of p53 tumor-suppressor protein is a poor indicator of prognosis for canine cutaneous mast cell tumors

Eighty-three canine cutaneous mast cell tumors were graded histologically and evaluated immunohistochemically for p53 tumor-suppressor protein expression. An avidin-biotin immunohistochemical protocol incorporated a rabbit polyclonal antibody (CM-1) directed against normal and mutant p53 protein. Positive staining was observed in 44.6% (37/83) of tumors and included 50% (12/24) of grade I (well differentiated) tumors, 46.9% (23/49) of grade II (intermediate differentiation) tumors, and 20% (2/10) of grade III (poorly differentiated) tumors. A statistically significantly higher proportion (P < 0.019) of tumors from the head and neck (83.3%, 10/12), stained positive for p53 than tumors from the thorax, back, abdomen, and axilla (39.4%, 13/33), legs (35.7%, 10/28), or prepuce, scrotal, or inguinal areas (44.4%, 4/9). No statistically significant difference between p53 labeling and histologic grade, breed, or tumor size was present. Survival data were available for 53/83 (63.9%) of dogs. Positive reactivity for p53 was observed in 47% (25/53) of tumors within this group, with 57.9% (11/19) of grade I, 43.3% (13/30) of grade II, and 25% (1/4) of grade III tumors labeled. Mean survival time for the 53 dogs was 12.1 months. The median survival time for dogs with grade III tumors or tumors >5 cm was statistically significantly shorter (P < 0.0001) than for dogs with grades I and II or smaller tumors. Although p53 protein abnormalities may play a role in tumor development or behavior in some canine cutaneous mast cell tumors, immunoreactivity was not associated with lack of tumor differentiation, tumor locations previously shown to demonstrate aggressive biological behavior, breed predisposition, or survival times.     

Retrospective outcome evaluation for dogs with surgically excised,solitary Kiupel high‐grade,cutaneous mast cell tumours

Published outcomes for dogs with specifically high‐grade mast cell tumours (MCTs), controlled for clinical stage, are few. Clinical outcomes for 49 dogs with Kiupel high‐grade, clinical stage I, cutaneous MCTs were evaluated. Median survival time (MST) was 1046 days; 1 and 2‐year survival rates were 79.3% and 72.9%, respectively. At study end 24 dogs had died, 23 dogs were alive (median follow‐up 980 days) and 2 dogs were lost to follow‐up. Death was considered MCT‐related in 14 of 20 dogs with a known cause of death. Local tumour recurrence developed in nine dogs (18.4%); regional lymph node metastasis occurred in six dogs (12.2%); and a new MCT developed in 15 dogs (30.1%). Tumour location, histologic margin size and use of chemotherapy did not affect MST; increasing mitotic count (P = .001) and increasing tumour diameter (P = .024) were independently negatively prognostic. Six dogs that developed lymph node metastasis after surgery had worse MST (451 days) than 42 dogs that did not develop metastasis (1645 days); (P < .001). Our study suggests that dogs with local surgical control of clinical stage I histologically high Kiupel grade cutaneous MCT may have a long survival time; especially those with smaller tumours and a lower mitotic count. Our results suggest that evaluation of staging information and mitotic count may be equally helpful as histologic grading when making a prognosis; and highlight the importance of not relying on histologic grade alone when predicting survival for dogs with MCT.     

Expression of the KIT protein (CD117) in primary cutaneous mast cell tumors of the dog.

Thirty-one canine cutaneous masses, diagnosed as mast cell tumors (MCT) by histopathologic analysis, were used to evaluate the immunohistochemical pattern of expression of KIT protein (CD117), a type III tyrosine kinase protein involved in mast cell growth and differentiation. Lesions were graded as I (well differentiated), II (intermediate differentiation), or III (poorly differentiated) according to the following morphologic features: invasiveness, cellularity and cellular morphology, mitotic index, and stromal reaction. Immunohistochemical KIT expression was compared with histologic grade and some histomorphologic features (cell differentiation and nuclear grade) evaluated separately. A possible predictive role of biologic behavior in MCTs for KIT expression was also investigated. Immunohistochemical analysis revealed three different patterns of KIT expression: a cytoplasmic diffuse pattern, a membranous pattern with immunostaining located on the cell surface, and a cytoplasmic perinuclear pattern, where KIT expression was detected in the cytoplasm of the neoplastic mast cells, close to the nucleus. Statistical analysis showed a close relationship between different KIT immunohistochemical patterns and histologic grade (P < 0.00000), cell differentiation (P < 0.00000), and nuclear grade (P < 0.0024). According to Kaplan-Meier-estimated survival curves compared by survival analysis, KIT expression was significantly associated with survival time (P = 0.037) but not cancer-free interval (P = 0.50). Similar to other well-known histomorphological features, KIT expression is a useful parameter of malignancy in cutaneous MCTs. KIT expression also predicted the biological behavior of the tumors in this study.     

Variation among pathologists in histologic grading of canine cutaneous mast cell tumors.

Ten veterinary pathologists at 1 veterinary institution independently assigned histologic grades to the same 60 canine cutaneous mast cell tumors (MCTs). There was significant variation among pathologists in grading the MCTs (P < 0.001). The probability of assigning a low grade was significantly higher for the pathologists in this study who use a published reference for histologic grading of canine cutaneous MCTs that allows subcutaneous MCTs or MCTs with mitotic figures to be included in the low-grade category (P < 0.0001 and P < 0.0001, respectively).     

Adjuvant medical therapy provides no therapeutic benefit in the treatment of dogs with low‐grade mast cell tumours and early nodal metastasis undergoing surgery

Lymph node (LN) metastasis is a negative prognostic factor in dogs with cutaneous mast cell tumours (cMCTs). While elective lymphadenectomy of metastatic LNs improves outcome, the benefit of adjuvant medical therapy in dogs with early metastatic (HN2) LNs is debated. The aim of this retrospective multicentre study was to evaluate the therapeutic benefit of adjuvant medical therapy following surgical removal of the primary low‐grade cMCT (Patnaik grade 1‐2 and Kiupel low‐grade) and lymphadenectomy of HN2 LNs by analysing survival rates and patterns of recurrence. Seventy‐three dogs were included: 42 received adjuvant medical treatment (chemotherapy and/or kinase inhibitors), and 31 did not. The median follow‐up time for medically treated dogs was 619 days: two experienced local recurrence, three nodal relapse and four distant relapse. For dogs undergoing surgery only, the median follow‐up time was 545 days. None of them experienced local recurrence, nodal, or distant relapse. Time to progression was significantly shorter in dogs receiving adjuvant medical treatment (P = .021). A similar tendency was observed for overall survival (P = .056). The current study shows that dogs with low‐grade cMCTs, that undergo surgical excision of the primary tumour and elective lymphadenectomy of the HN2 regional LN harbour a good prognosis. The use of adjuvant medical treatment in these dogs does not seem to provide any benefit in terms of progression and survival.     

Pre-operative neoadjuvant vinblastine-prednisolone in canine mast cell tumours: A single-centre retrospective cohort study

Neoadjuvant chemotherapy can be used in canine mast cell tumours (MCTs) to optimise surgical margins or to enable marginal excision in challenging locations. The objective of this study was to describe the outcome of dogs with cutaneous and subcutaneous MCTs treated with neoadjuvant vinblastine-prednisolone (NA-VP). Records of treatment-naïve dogs with cutaneous/subcutaneous MCT that received NA-VP were reviewed including signalment, indication for NA-VP, staging results, clinical response, surgical data and histopathology reports. For dogs with post-operative follow-up ≥365 days, predictive factors for local recurrence (LR) were evaluated. Forty-four dogs were included. NA-VP was indicated to optimise surgical margins (group MARG) in 19 dogs (43.2%) and to enable surgery (group MORB) in 25 dogs (56.8%). Complete and partial response were documented in 40.9% of dogs and 30 dogs (68.2%) underwent surgery. The indication for NA-VP was significantly associated with undergoing surgery (p < .001) on multivariable analysis. Twelve (48%) and 18 dogs (94.7%) underwent surgery in the group MORB and MARG, respectively. Five dogs (16.7%) experienced wound dehiscence. Complete excision was achieved in 14 dogs (46.7%). In dogs undergoing surgery with ≥365 days of follow-up, LR was documented in five cases (20.8%). None of the factors analysed including mitotic count, completeness of excision and response to NA-VP were associated with LR; notably, LR occurred in 3/11 (27.2%) completely excised MCTs. In a pre-operative setting, NA-VP appears safe and could be beneficial in selected cases. Prognostic factors such as clinical response, mitotic count and completeness of excision should be interpreted with caution following NA-VP.     

Evaluation of surgical margins required for complete excision of cutaneous mast cell tumors in dogs

OBJECTIVE: To determine whether neoplastic mast cells extended into tissue 1, 2, or 3 cm laterally or deeper than 1 fascial plane from the visible edge of cutaneous mast cell tumors (MCTs) in dogs. DESIGN: Prospective study. ANIMALS: 21 client-owned dogs with > or = 1 cutaneous MCT PROCEDURES: After preparation for surgery, each dog's skin was marked 1, 2, and 3 cm from the tumor edge at 0 degrees, 90 degrees, 180 degrees, and 270 degrees. At each 3-cm mark, deep fascia was exposed and sutured to the skin; the tumor was excised in routine fashion and fixed in formalin. Tumors were graded; margins were examined histologically for neoplastic mast cells. RESULTS: 23 cutaneous MCTs in 21 dogs were included in this study. Fifteen (65%) tumors were located on the trunk, 5 (22%) on the hind limbs, and 3 (13%) on the head and neck. There were 3 (13%) grade-I and 20 (87%) grade-II tumors. All grade-I tumors were completely excised at all margins. Seventy-five percent of the grade-II tumors were completely excised at the 1-cm margin, and 100% were completely excised at the 2-cm margin. Two grade-II MCTs located on the hind limbs of dogs were excised with a complete but close (within 1 mm) deep margin. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that a 2-cm lateral margin and a deep margin of 1 fascial plane appear to be adequate for complete excision of grade-I and -II MCTs in dogs.