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

Feline cutaneous mast cell tumours: a UK-based study comparing signalment and histological features with long-term outcomes

Feline cutaneous mast cell tumours (MCTs) are the second most common skin tumour in cats; but, unlike in dogs, there is currently no histological grading system for this type of tumour. This study recorded the signalment and anatomical location from a total of 287 records from MCTs submitted to a UK commercial diagnostic laboratory. Questionnaires to submitting practices were used to obtain follow-up data, and the histological features of 86 tumours were evaluated from 69 cats with a known outcome. Twelve of the 69 cats (17.4%) died of MCTs, with significantly lower survival times. The median age of cats presenting with MCTs was 11 years (range 5 months-19 years), with no sex or neutered status predilection. Some pedigree breeds were more susceptible to MCTs, particularly the Siamese, Burmese, Russian Blue and Ragdoll. The head was the most common site in younger cats, compared with the trunk in older cats. The number of tumours had no effect on survival. A new subcategory of well-differentiated MCTs with prominent multinucleated cells is described, and three of the five cats with this novel form died from MCT-related disease. There was an association between mitotic index and survival time. However, there was no significant association between histological type and survival.

C-kit as a prognostic and therapeutic marker in canine cutaneous mast cell tumours: From laboratory to clinic

Cutaneous mast cell tumours (MCTs) are some of the most common canine neoplasms and their variable and often aggressive biological behaviour makes them particularly challenging for the veterinary practitioner. Over the years, scientists have accumulated a wealth of knowledge on these tumours and developed better prognostic markers and targeted therapies, mostly focused on inhibiting c-kit, a protein that plays a major role in the biopathology of MCTs. Masitinib and toceranib, targeted inhibitors of c-kit and other receptor tyrosine-kinases (RTKs), offer the promise of improving the outcome of patients with aggressive MCTs. Much of the available knowledge on MCTs is dispersed, making it difficult for practitioners to benefit when consulting a pathologist or making therapeutic decisions. This article seeks to bring together current knowledge on the biopathology of MCTs, reviewing prognostic markers and their applications, and the development of c-kit inhibitors in the context of the basic cellular, molecular and pathological features of MCTs. Future perspectives following recent biopathological data and experimental therapeutic approaches are also addressed.

Current concepts in oncologic surgery in small animals

Surgical oncology is experiencing rapid transition in veterinary medicine. Mast cell tumors and soft tissue sarcomas are two of the most common neoplasms in small animal patients. Clinicians should be familiar with the need for staging and the procedures involved in treating patients with these tumors. Clinicians should be comfortable with available adjuvant therapies and when to use them in certain patients.

Useful immunohistochemical indicators in canine mast cell tumours

Morphological and immunohistochemical analysis of 45 canine mast cell tumours was performed to determine whether the proteins examined are useful for a more precise description of tumour morphology and a more reliable determination of the prognosis in patients. Tissue sections were stained according to the standard haematoxylin and eosin (HE) technique and with toluidine blue to demonstrate cytoplasmic granules. Immunohistochemical studies were performed, using the cell markers CD117 (c-kit), p16 and von Willebrand factor (FVIII). In CD117 three different staining patterns were observed: (1) membranous reaction, (2) intense staining of cytoplasm, and (3) a diffuse, delicate cytoplasmic reaction. Von Willebrand antibody was evaluated on the basis of the number of blood vessels stained. p16 expression was evaluated by scoring positive nuclear reaction. Positive expression was demonstrated for all examined antigens, but their level of expression differed depending on the grades of tumour malignancy. Statistical analysis of the results documented a pronounced positive correlation between the markers studied and the grade of tumour malignancy (P < 0.001). It was shown that each of the cell markers examined represents a useful prognostic indicator for patients with mast cell tumours. The calculated correlation coefficients demonstrate a strong association between the expressions of CD117, FVIII and p16, and the histological malignancy of a tumour.

Recurrence rates and clinical outcome for dogs with grade II mast cell tumours with a low AgNOR count and Ki67 index treated with surgery alone

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.

Prevalence and risk factors for mast cell tumours in dogs in England

Background

Mast cell tumour (MCT) appears to be a frequent tumour type in dogs, though there is little published in relation to its frequency in dogs in the UK. The current study aimed to investigate prevalence and risk factors for MCTs in dogs attending English primary-care veterinary practices.

Methods

Electronic patient records from practices participating in the VetCompass animal surveillance project between July 2007 and June 2013 were searched for MCT diagnosis. Various search terms and standard diagnostic terms (VeNom codes) identified records containing MCT diagnoses, which were evaluated against clinical criteria for inclusion to the study. MCT prevalence for the entire dataset and specific breed types were calculated. Descriptive statistics characterised MCT cases and multivariable logistic regression methods evaluated risk factors for association with MCT (P < 0.05).

Results

Within a population of 168,636 dogs, 453 had MCT, yielding a prevalence of 0.27% (95% confidence interval (CI) 0.24% - 0.29%). The highest breed type specific prevalences were for the Boxer at 1.95% (95% CI 1.40% - 2.51%), Golden Retriever at 1.39% (0.98% - 1.81%) and Weimaraner at 0.85% (95% CI 0.17% to 1.53%). Age, insurance status, neuter status, weight and breed type were associated with MCT diagnosis. Of dogs of specific breed type, the Boxer, Pug and Staffordshire Bull Terrier showed greater odds of MCT diagnosis compared with crossbred dogs. Conversely, the German Shepherd Dog, Border Collie, West Highland White Terrier, Springer Spaniel and Cocker Spaniel had reduced odds of MCT diagnosis compared with crossbred dogs. No association was found between MCT diagnosis and sex.

Clinical significance

This study highlights a clinically significant prevalence of MCT and identifies specific breed types with predisposition to MCT, potentially aiding veterinarian awareness and facilitating diagnosis.

Uterine mast cell tumor: a clinical and cytohistopathological study

Background

Mast cells are one of the characteristic factors in angiogenesis, growth, and metastatic spread of tumors. Further studies are suggested to determine the type of these cells which might be useful in the assessment of biological nature of the tumor and its future treatment modality. Few studies have evaluated mast cell infiltration in visceral tumors, especially uterine tumors.

Case presentation

In this study, age, sex, death rate, and histologic patterns were in agreement with those of previous reports on canine mast cell tumors. Cytopathology assays are widely used to prognosticate canine uterine mast cell tumors (MCT). There is limited information about these prognostic assays used on MCT that arise in the uterine. The anisocytosis and anisocytosis and giant cells were present in the tumor. Furthermore, the tumor had nuclear atypia with scattered multinucleated cells and prominent nucleoli and tumor were classified as poorly granulated. Under microscopic examination, we observed diffuse infiltration and proliferation of tumor cells from the uterine different area and the infiltrative characteristics and distribution patterns of neoplastic cells were observed. This tumor consisted of sheets and cords of uniform round cells with discrete cytoplasmic margins. Microscopically, the neoplastic masses were poorly-demarcated and lacked capsules and tumor cell usually showed a distinct cell boundary. Nevertheless, the neoplastic cells were located between collagen bundles forming small clusters and sheets and had large, centrally located, round to ovoid nuclei. In addition, eosinophils were scattered among the mast cells at the periphery of the masses. The presence of eosinophils and the observation, at high magnification, of cells with cytoplasmic metachromatic granules.

Conclusion

Based on these findings, a diagnosis of poorly-differentiated mast cell tumor was made and data histologic grading was available for tumor. Neoplasm was poorly differentiated or gradeIII.

A retrospective review of treatment and response of high-risk mast cell tumours in dogs

This retrospective case series evaluates survival outcome of 94 dogs with high metastatic risk mast cell tumours (MCT). Patients were treated with a cytotoxic chemotherapy protocol or the tyrosine kinase inhibitor masitinib, in the presence of gross disease or as an adjunct to surgical resection of the primary tumour. In patients presenting with metastatic disease, surgical resection of the primary tumour with adjunctive therapy with any chemotherapy incurred a significant survival advantage [median survival time (MST): 278 days] compared to patients receiving chemotherapy without surgical excision of the primary tumour (MST: 91 days, P < 0.0001). Patients with a surgically excised Patnaik grade II tumour and high Ki-67 in the absence of metastatic disease treated with vinblastine and prednisolone showed a significantly longer survival (MST: 1946 days) than those treated with masitinib (MST: 369 days, P = 0.0037). Further prospective case-controlled clinical trials of high-risk MCTs are required to make precise evidence-based treatment decisions for individual patients.

p62/Sequestosome-1: Mapping Sites of Protein-Handling Stress in Canine Cutaneous Mast Cell Tumors

Canine cutaneous mast cell tumors (MCT) are common, frequently malignant neoplasms that are currently graded histologically for provision of prognostic information. Continuing evidence of subsets of MCT within certain grades (with differing survival times) indicate the need for biomarkers that will facilitate better patient stratification and also provide further information on the biological processes involved in progression. We decided to investigate the expression of p62/sequestosome-1 (p62/SQSTM1), a stress-inducible "hub protein" found in all cell types that shuttles rapidly between the nucleus and cytoplasm and is known to play important roles in protein handling and tumorigenesis. The identity of canine p62/SQSTM1 was confirmed in silico and by validation of a commercial antibody using both Western blotting and functional (pharmaceutical-based) analyses in cell culture. Using immunohistochemistry, 3 patterns of p62 expression were identified based on the predominant intracellular localization, that is, nuclear, mixed (nuclear and cytoplasmic), and cytoplasmic. There was a highly significant association with the 2-tier (Kiupel) grade (P < .0001), with all p62-nuclear immunoreactivity being associated with low grade and most p62-cytoplasmic immunoreactivity (93%) with high grade. Most but not all mixed nuclear-cytoplasmic labeling occurred in low-grade MCT; in other (human) tumor types, this pattern has been interpreted as borderline malignant. These data indicate that there is a shift in protein-handling stress from the nucleus to the cytoplasm in association with increasing malignancy in MCT. Studies to identify the processes and drug-able targets involved in this progression are ongoing.

Canine mast cell tumors: diagnosis, treatment, and prognosis

Mast cell tumors (MCTs) are the most common malignant skin cancer in dogs, and significant variability exists in their biological behavior. Most MCTs are cured with appropriate local therapy, but a subset shows malignant behavior with the potential to spread to lymph nodes, liver, spleen, and other areas and to thus become a systemic cancer. Because of this variable behavior, it is difficult to predict how any individual tumor is going to behave. The variability thus creates uncertainty in deciding what a particular dog’s prognosis is, whether staging tests to assess for metastasis are needed, and even what treatments will be necessary for best outcome. In addition to controversies over the potential for development of systemic disease, or diffuse metastasis, controversies also exist over what treatment is needed to best attain local control of these tumors. This article will briefly discuss the diagnosis of MCTs in dogs and will summarize the literature in regards to the controversial topics surrounding the more aggressive form of this disease, with recommendations made based on published studies.

Evaluation of a modified proportional margins approach for surgical resection of mast cell tumors in dogs: 40 cases (2008-2012)

OBJECTIVE

To evaluate a modified proportional margins approach to resection of mast cell tumors (MCTs) in dogs.

DESIGN

Retrospective case series.

ANIMALS

40 dogs with subcutaneous and cutaneous MCTs undergoing curative intent surgery.

PROCEDURES

Medical records were searched to identify dogs with a cytologically or histologically confirmed diagnosis of MCT that had not previously been treated surgically and that had undergone full oncological staging. In those dogs, tumors were resected with lateral margins equivalent to the widest measured diameter of the tumor and a minimum depth of 1 well-defined fascial plane deep to the tumor. Surgical margins were evaluated histologically. Cutaneous tumors were graded by use of the Patnaik system and the 2-tier system described by Kiupel et al. The prognosis for subcutaneous tumors was assessed in accordance with published recommendations. Follow-up information on dog health status was obtained through clinical examination, the dog owners, and the referring veterinarians.

RESULTS

The 40 dogs had 47 tumors. Forty-one (87%) tumors were cutaneous, and 6 (13%) were subcutaneous. On the basis of the Patnaik system, 21 (51%) cutaneous tumors were considered grade I, 18 (44%) were considered grade II, and 2 (5%) were considered grade III. On the basis of the Kiupel system, 37 (90%) cutaneous tumors were considered low grade, and 4 (10%) were considered high grade. The prognosis for the 6 subcutaneous tumors was classified as likely resulting in a shorter (2) or longer (4) survival time. Forty tumors were deemed to have been excised with clear margins and 7 with incomplete margins. Local recurrence was not recorded for any dog but was suspected for 1 (2%) tumor, although not confirmed. Interval from tumor excision to follow-up ranged from 30 to 1,140 days (median, 420 days).

CONCLUSIONS AND CLINICAL RELEVANCE

The modified proportional margins system resulted in satisfactory local disease control in dogs with MCTs.

Global gene expression analysis of canine cutaneous mast cell tumor: could molecular profiling be useful for subtype classification and prognostication?

Prognosis and therapeutic management of dogs with cutaneous mast cell tumors (MCTs) depend on clinical stage and histological grade. However, the prognostic value of this latter is still questionable. In the present study, MCT transcriptome was analyzed to identify a set of candidate genes potentially useful for predicting the biological behavior of MCTs. Fifty-one canine MCT biopsies were analyzed. Isolated and purified total RNAs were individually hybridized to the Agilent Canine V2 4x44k DNA microarray. The comparison of reference differentiated and undifferentiated MCT transcriptome revealed a total of 597 differentially expressed genes (147 down-regulated and 450 up-regulated). The functional analysis of this set of genes provided evidence that they were mainly involved in cell cycle, DNA replication, p53 signaling pathway, nucleotide excision repair and pyrimidine metabolism. Class prediction analysis identified 13 transcripts providing the greatest accuracy of class prediction and divided samples into two categories (differentiated and undifferentiated), harboring a different prognosis. The Principal Component Analysis of all samples, made by using the selected 13 markers, confirmed MCT classification. The first three components accounted for 99.924% of the total variance. This molecular classification significantly correlated with survival time (p = 0.0026). Furthermore, among all marker genes, a significant association was found between mRNA expression and MCT-related mortality for FOXM1, GSN, FEN1 and KPNA2 (p<0.05). Finally, marker genes mRNA expression was evaluated in a cohort of 22 independent samples. Data obtained enabled to identify MCT cases with different prognosis. Overall, the molecular characterization of canine MCT transcriptome allowed the identification of a set of 13 transcripts that clearly separated differentiated from undifferentiated MCTs, thus predicting outcome regardless of the histological grade. These results may have clinical relevance and warrant future validation in a prospective study.

The Prognostic Value of Lymph Node Metastasis with Grade 2 MCTs in Dogs: 55 Cases (2001–2010)

This study evaluates a series of dogs diagnosed with grade 2 cutaneous mast cell tumors (MCTs) with concurrent lymph node (LN) metastasis. All dogs had surgical excision of the primary tumor. The presence of metastasis was confirmed with either histopathology (n = 35) or cytology (n = 20). There was no significant difference in survival times (STs) between dogs with and without LN metastasis. Median survival time (MST) was not reached at 65.9 mo. LN palpation was a poor predictor of metastasis (sensitivity, .71; specificity, .54). Tumor location was the only prognostic factor for survival in this series of dogs. ST was greater for dogs that had removal of their metastatic LN. This study suggests that in dogs with grade 2 MCTs, outcome may not be affected by the presence of LN metastasis; however, removal of the metastatic LN may prolong survival.

The Relevance of CD117-Immunocytochemistry Staining Patterns to Mutational Exon-11 in c-kit Detected by PCR from Fine-Needle Aspirated Canine Mast Cell Tumor Cells

Canine cutaneous mast cell tumors (MCT) are the lethal skin tumors. The biological behavior of the MCT cells is quite varied and unpredictable. Almost MCT dogs usually require a rapid diagnosis and therapy. However, MCT diagnosis and prognosis are still dependent on histopathology which is rather inconvenient, time-consuming, painful, and harmful for some cases. Indeed, MCT can be easily accessible using fine-needle aspiration (FNA). In this study, our biopsy specimens were classified as low- and high-grade MCT based on the novel 2-tier histopathologic grading system. We have demonstrated the usage of fine-needle aspirated MCT cells (FNA-MCT cells) from these specimens as a primary cell source to study the distribution of CD117-immunocytochemistry (CD117-ICC) staining patterns and the frequency of internal tandem duplication- (ITD-) mutant exon-11 of c-kit. The result has substantially shown that there were three staining patterns identified in the cells. Only paranuclear pattern was significantly increased in the cells from high-grade MCT. Altogether, the ITD-mutant exon-11 was also detectable only in these cells. Therefore, the result has supported our hypothesis that there was an increased opportunity to observe a higher CD117-ICC staining pattern and exon-11 mutation in high-grade MCT; even these two parameters may not precisely indicate a histopathological grade.

Histologic grading of canine mast cell tumor: is 2 better than 3?

Mast cell tumor (MCT) is a common canine cutaneous neoplasm with variable biological behavior. A 2-tier histologic grading system was recently proposed by Kiupel et al to reduce interobserver variation and eliminate prognostic uncertainty of the Patnaik system. This study compared the ability of these 2 grading systems to predict survival in a cohort of dogs with MCTs. However, surgical margins were unknown, and the risk of developing new/metastatic MCTs was not studied. Histologic grade was assessed according to both systems for 137 surgically resected cutaneous MCTs. The relationship between grade and survival was evaluated. According to the Patnaik system, 18 MCTs (13.1%) were classified as grade I, 83 (60.6%) as grade II, and 36 (26.3%) as grade III. Grade III was associated with a poorer prognosis (P < .001), but no significant difference between grades I and II was detected. Grading according to the Patnaik system was based on consensus grading among 3 pathologists, and interobserver variability was not considered. All grade I MCTs were low grade in the Kiupel system, and all grade III were high grade. Among grade II, 71 (85.6%) were low grade, and 12 (14.4%) were high grade, with a 1-year survival probability of 94% and 46%, respectively (P < .001). The 2-tier system had a high prognostic value and was able to correctly predict the negative outcomes of some grade II MCTs. Data also confirm that histologic grading cannot predict biological behavior of each MCT and should be supplemented with molecular methods for more accurate prognostication.

Reaction phenotyping of vinblastine metabolism in dogs

Vinblastine is a vinca alkaloid used either as a single agent or in combination therapy for the treatment of canine mast cell tumours and lymphomas. The objective of this study was to determine which isoform of cytochrome P450 enzyme is responsible for the majority of vinblastine metabolism in dogs. A panel of eight recombinant canine cytochrome P450 enzymes (CYP1A1, CYP1A2, CYP3A12, CYP3A26, CYP2B11, CYP2C41, CYP2C21 and CYP2D15) were incubated in vitro with vinblastine. Findings were confirmed by the use of canine polyclonal antibodies of cytochrome P450 enzymes (CYP1A1, CYP3A12, CYP2B11 and CYP2C21) that were pre-incubated with individual and pooled hepatic microsomes that were purified from canine liver. Substrate depletion was observed in the presence of recombinant CYP3A12, whereas depletion did not substantially occur when microsomes were pre-incubated with polyclonal antibodies against CYP3A12. These findings confirmed that CYP3A12 is the major cytochrome P450 isoform responsible for the metabolism of vinblastine in dogs.

Cutaneous mast cell tumor (Mastocytoma): cyto- histopathological and haematological investigations

Cutaneous mast cell tumours (MCTs) are the most common skin tumours in dogs. Due to the prevalence of canine MCTs and the variable biologic behavior of this disease, accurate prognostication and a thorough understanding of MCT biology are critical for the treatment of this disease. A cytologic diagnosis of mast cell tumor with evidence of prior hemorrhage was made, and the masses were surgically removed. Cytological evaluation of fine-needle aspirates from the cutaneous mass from the axillary comprised many well-differentiated, highly granulated mast cells with moderate numbers of eosinophils. Nuclei were varied in size and shape with high nuclear’to’cytoplasmic ratio, prominent nucleoli, marked atypical and mitotic figures. Microscopically, mass consisted of sheets of neoplastic round cells that formed nonencapsulated nodules in the dermis and infiltrated into the adjacent dermal collagen, and also there was diffuse subcutis invasion of round to pleomorphic tumor cells. Tumor cells had moderate to abundant cytoplasm, round to ovoid nuclei with scattered chromatin, and mitotic figures. In this tumor, cytoplasmic granules showed atypical metachromasia. In addition, eosinophils were scattered among the mast cells at the periphery of the nodules. The presence of eosinophils and the observation, at high magnification, of cells with cytoplasmic metachromatic granules. Invasion of the deep subcutaneous fat or cutaneous muscles were a common feature of grade III tumour. Finally, a diagnosis of grade III cutaneous mast cell tumor was made.

Scrotal tumors in dogs: a retrospective study of 676 cases (1986-2010)

The objective of this study was to determine common tumor types that occur on the canine scrotum in relation to other cutaneous locations and to identify potential risk factors for specific scrotal tumor development. A retrospective study was conducted and the database of pathology reports from the Surgical Pathology Service of the Department of Pathology and Toxicology, School of Veterinary Medicine, University of Pennsylvania from 1986 to 2010 was searched for canine neoplastic scrotal and non-scrotal cutaneous lesions. Neoplastic lesions were evaluated based on diagnosis, breed, age, and number and location of tumors (scrotal versus non-scrotal cutaneous). Mast cell tumor, melanocytoma, malignant melanoma, vascular hamartoma, hemangiosarcoma, hemangioma, and cutaneous histiocytoma were the most common tumor types identified on the canine scrotum. Breed predispositions and mean age at diagnosis were identified for each tumor type and should be considered when planning surgical excision of a canine scrotal tumor.

Concordance of c-kit mutational status in matched primary and metastatic cutaneous canine mast cell tumors at baseline

Background

Mutation analysis of proto‐oncogene c‐kit (c‐kit) is advisable before starting treatment with tyrosine kinase inhibitors in dogs with mast cell tumor (MCT), including those with metastatic disease. Testing is usually performed on primary tumors, assuming that c‐kit mutation status does not change in metastasis.

Hypothesis/Objectives

To give an insight into the mutational processes and to make a recommendation on the use of c‐kit mutational analysis in the clinical setting.

Animals

Twenty‐one client‐owned dogs with metastatic MCT.

Methods

Dogs undergoing resection or biopsy for both primary and matched metastatic MCT were prospectively enrolled. Total RNA or DNA was extracted from primary MCT and corresponding metastases. Exons 8, 9, and 11 were amplified by PCR and sequenced. Genetic features between primary MCT and metastases were compared. Their correlation with clinicopathologic features was investigated.

Results

Concordance (mutated or wild‐type) of mutational status, evaluable in 21 primary and matched metastatic (20 nodal and 1 splenic) MCTs, was 100%. Three new c‐kit mutations were identified. No significant correlation was detected between c‐kit mutation and clinicopathologic features.

Conclusions and Clinical Importance

Proto‐oncogene c‐kit mutational status is conserved between any primary and its matched secondary tumor, suggesting that both can be used for c‐kit mutational testing. Targeted therapies might be also used to treat metastatic disease.

Nasal-skin-fold transposition flap for upper lip reconstruction in a French bulldog

Upper-lip reconstruction after mast-cell tumor-resection in a French bulldog was achieved by using a transposition flap from the nasal-skin-fold and an oral mucosal flap. The new technique is an alternative for reconstruction of extensive upper-lip defects in brachycephalic dogs and achieves satisfactory functional and cosmetic results.

Histologic Characteristics and KIT Staining Patterns of Equine Cutaneous Mast Cell Tumors

Mast cell tumors are uncommon in horses and typically have a benign clinical course, but there are occasional reports of more aggressive behavior. The objective of this study was to review histologic features and KIT expression patterns of 72 previously diagnosed equine cutaneous mast cell tumors to determine if either is associated with clinical outcomes. Biopsy specimens were reviewed using histologic criteria derived from grading schemes, and KIT antibody expression patterns used in canine tumors and surveys were sent to referring veterinarians for follow-up clinical data. Arabians were overrepresented relative to the reference population. Most tumors were well differentiated with low mitotic rates (96%), and aberrant KIT staining patterns, as described in dogs, were uncommonly identified (12%). Associated clinical disease was uncommon and no tumors exhibited malignant behavior. Overall, KIT staining pattern and histologic features were not associated with poor clinical outcome or abnormal tumor behavior.

Aggressive local therapy combined with systemic chemotherapy provides long-term control in grade II stage 2 canine mast cell tumour: 21 cases (1999-2012)

This retrospective case series evaluates the outcome of 21 dogs with grade II stage 2 mast cell tumour (MCT) treated with adequate local therapy and adjuvant systemic chemotherapy (prednisone, vinblastine and CCNU). The median survival for all dogs was 1359 days (range, 188-2340). Median disease-free interval was 2120 days (149-2325 days). Dogs treated with surgery and chemotherapy had shorter survival (median, 1103 days; 188-2010 days) than those that underwent surgery, radiation therapy and chemotherapy as part of their treatment (median, 2056 days; 300-2340 days). Two patients had local recurrence in the radiation field and four patients had de novo MCT. Distant metastasis was not observed in any dogs. The results of this study suggest that, in the presence of loco-regional lymph node metastasis in grade II MCT, the use of prednisone, vinblastine and CCNU after adequate local-regional therapy can provide a median survival in excess of 40 months.

Unilateral intraocular mastocytosis and anterior uveitis in a dog with subcutaneous mast cell tumors

A 9-year-old male castrated Scottish terrier was referred to the Radiation Oncology Service at the William R. Pritchard Veterinary Medical Teaching Hospital for palliative radiation therapy of an incompletely excised, recurrent subcutaneous mast cell tumor (MCT) located over the right scapula, and surgical removal of a perianal MCT. Three weeks after initial presentation and prior to the fifth radiation treatment, the patient was presented with cloudiness of the left eye of 3-7 days duration. Ophthalmic consultation revealed 3+ aqueous flare with a dependent, swirling component filling approximately one-third of the anterior chamber. Aqueocentesis was performed under general anesthesia. Cytology revealed mast cells with highly atypical morphology and considered most consistent with neoplasia. The patient died 7 months after pathologic diagnosis of MCT on the right shoulder and 2 months after the cytologic diagnosis of malignant mast cells in the left anterior chamber. To the authors' knowledge, this is the first report of intraocular involvement in a mammal with MCTs, described here as intraocular mastocytosis.

Relação da expressão de fatores de crescimento celular (IGF-1) e (SCF) com fatores prognósticos e o alvo da rapamicina em mamíferos (m-TOR) em mastocitomas cutâneos caninos

O mastocitoma cutâneo (MTC) é a neoplasia maligna mais comum na pele dos cães e seu comportamento biológico é muito variável. Dentre os fatores prognósticos estudados nos MTCs, a classificação histopatológica, o índice proliferativo e o padrão de expressão doc-KIT são os que apresentam uma associação mais relevante com o provável prognóstico deste tumor. O objetivo deste trabalho foi avaliar a expressão proteica de fator de crescimento semelhante à insulina tipo 1 (IGF-1), fator de célula tronco (SCF) e sua relação com o receptor tirosina quinase (c-KIT), alvo da rapamicina em mamíferos (m-TOR), grau histológico, índice proliferativo pelo KI-67e o número de figuras de mitose (IM) com dados clínicos de cães com MTCs . Foram utilizadas 133 amostras de MTCs, provenientes de 133 cães, dispostas em lâminas de microarranjo de tecidos (TMA). A técnica de imuno-histoquímica foi utilizada para a avaliação destas proteínas. Observou-se associação entre SCF e, a graduação histopatológica proposta em 2011, índice mitótico, proliferação celular (KI-67), escore de IGF-1, local da lesão, idade dos animais e padrão imuno-histoquímico do receptor c-KIT. A relação de dependência também foi observada entre IGF-1 e o porte dos animais, IM, m-TOR e c-KIT. A expressão de SCF teve relacção com a agressividade dos MTCs caninos, uma vez que foi mais freqüente em MTCs com c-KIT citoplasmático. A relação entre a expressão de IGF-1, SCF, c-KIT e m-TOR pode estar associada à integralização de suas vias de ação. A expressão de IGF-1 está associada à MTCs em cães de porte grande.

Rapid Evaluation of Mutant Exon-11 inc-kitin a Recurrent MCT Case Using CD117 Immunocytofluorescence, FACS-Cell Sorting, and PCR

A 13-year-old, poodle-mixed, male dog was referred to the oncology unit in our faculty’s small animal teaching hospital with the problem of rapid recurrent MCT. The owner and the veterinarian would like to use a tyrosine kinase inhibitor (TKI) for the dog. Therefore, fine-needle aspiration (FNA) was performed to collect the MCT cells and these cells were submitted to our laboratory for the detection of internal-tandem-duplicated (ITD) mutation of exon-11 inc-kit, prior to the treatment. The aim of this paper is to demonstrate the use of combinatorial protocol for the rapid evaluation of ITD mutation in MCT cells harvested by FNA. However, there was no ITD-mutant exon-11 that had been observed in this case.

Tandem duplication of KIT exon 11 influences the proteome of canine mast cell tumours

Mutations with permanent activation of the stem cell factor receptor KIT have been identified as one potential cause for canine cutaneous mast cell tumours (MCTs). The exact changes in global gene expression patterns associated with permanent activation of KIT in these tumours are unknown. The present study compares, by the use of two dimensional difference gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, the proteomes of canine MCTs, with and without KIT exon 11 tandem duplication. Fifteen differentially expressed proteins were identified in mutated MCTs. These are mainly involved in cytoskeleton structure and cell motility (ACTR2, ACTB and CAPPA1), cell signalling (ARHGDIA) and lipid metabolism (ALOX15 and ACSBG4), or are serum proteins. The results therefore support the notion that KIT mutation is associated with changes in the proteome of affected cells with a major effect on the composition of the cytoskeletal proteome and cell motility proteins. No overlaps were identified when the results were compared with a recent study on the proteomic differences between low- and high-grade tumours, suggesting that KIT-mutated tumours may be regarded as a separate entity of high-grade tumours with potential relevance to therapeutic strategies.