Immunohistochemical and clinical evaluation of p53 in canine cutaneous mast cell tumors

Genetic Changes in Mastocytes and Their Significance in Mast Cell Tumor Prognosis and Treatment

Mast cell tumors are a large group of diseases occurring in dogs, cats, mice, as well as in humans. Systemic mastocytosis (SM) is a disease involving the accumulation of mast cells in organs. KIT gene mutations are very often seen in abnormal mast cells. In SM, high KIT/CD117 expression is observed; however, there are usually no KIT gene mutations present. Mastocytoma (MCT)-a form of cutaneous neoplasm-is common in animals but quite rare in humans. KIT/CD117 receptor mutations were studied as the typical changes for human mastocytosis. In 80% of human cases, the KIT gene substitution p.D816H was present. In about 25% of MCTs, metastasis was observed. Changes in the gene expression of certain genes, such as overexpression of the DNAJ3A3 gene, promote metastasis. In contrast, the SNORD93 gene blocks the expression of metastasis genes. The panel of miR-21-5p, miR-379, and miR-885 has a good efficiency in discriminating healthy and MCT-affected dogs, as well as MCT-affected dogs with and without nodal metastasis. Further studies on the pathobiology of mast cells can lead to clinical improvements, such as better MCT diagnosis and treatment. Our paper reviews studies on the topic of mast cells, which have been carried out over the past few years.

Validation of p53 Immunohistochemistry (PAb240 Clone) in Canine Tumors with Next-Generation Sequencing (NGS) Analysis

In human medicine, p53 immunohistochemistry (IHC) is a common method that is used for the identification of tumors with TP53 mutations. In veterinary medicine, several studies have performed IHC for p53 in canine tumors, but it is not known how well it actually predicts the mutation. The aim of this study was to estimate the accuracy of the IHC method for p53 (clone PAb240) using a lab-developed NGS panel to analyze TP53 mutations in a subset of malignant tumors in dogs. A total of 176 tumors were analyzed with IHC and then 41 were subjected to NGS analysis; among them, 15 were IHC positive and 26 were negative, and 16 out of 41 (39%) were found to be inadequate for NGS analysis. Excluding the non-evaluable cases at NGS, of the remaining eight IHC-positive cases, six were mutants and two were wild-type. Among the 17 IHC-negative cases, 13 were wild type, and 4 were mutants. The sensitivity was 60%, specificity was 86.7%, and the accuracy was 76%. These results suggest that when using IHC for p53 with this specific antibody to predict mutation, up to 25% wrong predictions can be expected.

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

Mast cell tumors (MCTs) are hematopoietic neoplasms composed of mast cells. It is highly common in dogs and is extremely important in the veterinary oncology field. It represents the third most common tumor subtype, and is the most common malignant skin tumor in dogs, corresponding to 11% of skin cancer cases. The objective of this critical review was to present the report of the 2nd Consensus meeting on the Diagnosis, Prognosis, and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors, which was organized by the Brazilian Association of Veterinary Oncology (ABROVET) in August 2021. The most recent information on cutaneous and subcutaneous mast cell tumors in dogs is presented and discussed.

A Double Histochemical/Immunohistochemical Staining for the Identification of Canine Mast Cells in Light Microscopy

Immunohistochemistry (IHC) is a widely used technique in diagnostic pathology, but the simultaneous analysis of more than one antibody at a time with different chromogens is rather complex, time-consuming, and quite expensive. In order to facilitate the identification of mast cells (MCs) during immunohistochemical analysis of membrane and/or nuclear markers, we propose a new staining method that includes the association of IHC and toluidine blue as a counterstain. To achieve this goal, we tested c-kit, Ki67, and cannabinoid receptor 2 on several cases of cutaneous canine mast cell tumors (MCTs), cutaneous mastocytosis, and atopic dermatitis. The results obtained show how this double staining technique, although limited to non-cytoplasmic markers and of little use in poorly differentiated MCTs in which MC metachromasia is hard to see, can be used during the evaluation of nuclear and/or membranous immunohistochemical markers in all canine cutaneous disorders, especially if characterized by the presence of a low number of MCs. It can help to evaluate those MCTs in which neoplastic MCs must be clearly distinguished from inflammatory cells that can infiltrate the tumor itself, in facilitating the calculation of the Ki67 index. Moreover, it can be used to study the expression of new markers in both animal and human tissues containing MCs and in MC disorders.

Prognostic value of immunohistochemical markers in canine cutaneous mast cell tumours: A systematic review and meta-analysis

Histological grading systems remain cornerstones in the prognosis of canine cutaneous mast cell tumours (MCTs), but the distinct biological behaviour of each tumour often necessitates the use of complementary markers. Although a plethora of immunohistochemical markers have been proposed as prognostic factors, few are presently applied in routine diagnosis. This systematic review and meta-analysis was designed to establish which immunohistochemical markers have verifiable prognostic value for cutaneous MCTs in dogs. A Boolean search of five databases identified 200 articles for screening, of which 73 were selected for full-text assessment and 24 ultimately included in the systematic review. Odds Ratio (OR) was adopted as the summary measure for subsequent meta-analysis but only 15 articles, relating to the immunomarkers Ki-67 (9), KIT (5), and BAX (2), provided either a value for OR or sufficient data to calculate this statistic. Meta-analysis verified that canine cutaneous MCTs with elevated expression of Ki-67 or BAX, as well aberrant immuno-expression of KIT, showed an increased odds of death, with respective OR values of 11.2 (95% CI 6.3-20.0; p < .01), 9.9 (95% CI 1.3-73.6; p = .03), and 4.1 (95% CI 1.1-15.3; p = .03). Despite KIT, Ki67, and BAX arise as suitable prognostic factor for canine MCTs, this study highlighted the lack of important clinical and statistical data in many published articles, rendering it impossible to complete the meta-analysis of several potentially valuable immunohistochemical markers.

Identification of p53 gene alterations in canine mammary tumours using polymerase chain reaction and direct sequence analysis

Mammary tumours are mentioned as the most common tumours in female dogs and approximately half of them are detected malignant. p53 gene mutations are demonstrated to be the most common genetic alteration in canine mammary tumours. The present study was conducted to evaluate exon-1 of p53 gene mutations in tissue samples of canine mammary tumours by PCR and direct sequence analysis. After histopathological confirmation of the tissue sections by haematoxylin and eosin staining (10/26), deparaffinised samples were used for DNA extraction by silica gel method. Subsequently, p53 exon 1 was amplified through PCR assay using specific oligo nucleotide primers designed according to the canine DNA sequence available online. Microscopically, 10 out of 26 suspected tissue samples were recognised as malignant mammary gland tumours with various grades of malignancy. Surprisingly, one insertion of mutation was found in exon 1 of all examined samples corresponding to a sequence comprising 27 amino acids, between amino acids 30 to 57 in the p53 protein. Taken together, it seems that alteration of exon 1 p53 gene may lead to malignancy beha­viour, poor prognosis and short survival time in dogs with mammary carcinomas.

Dogs are man's best friend: in sickness and in health

With the median survival of 14.6 months following best available standard of care, malignant gliomas (MGs) remain one of the biggest therapeutic challenges of the modern time. Although the last several decades have witnessed tremendous advancement in our understanding of MG and evolution of many successful preclinical therapeutic strategies, even the most successful preclinical therapeutic strategies often fail to cross the phase I/II clinical trial threshold. One of the significant, but less commonly discussed, barriers in developing effective glioma therapy is the lack of a robust preclinical model. For the last 30 years, rodent orthotopic xenograft models have been extensively used in the preclinical setting. Although they provide a good basic model for understanding tumor biology, their value in successfully translating preclinical therapeutic triumph into clinical success is extremely poor. Companion dogs, which share the same environmental stress as their human counterparts, also spontaneously develop MGs. Dog gliomas that develop spontaneously in an immunocompetent host are very similar to human gliomas and potentially provide a stronger platform for validating the efficacy of therapeutic strategies proven successful in preclinical mouse models. Integrating this model can accelerate development of effective therapeutic options that will benefit both human subjects and pet dogs.

Immunohistochemical Expression of p27 and p21 in Canine Cutaneous Mast Cell Tumors and Histiocytomas

The objective of this study was to evaluate by immunohistochemical means the nuclear expression of p27 and p21 proteins in cutaneous mast cell tumors and histiocytomas of dogs. In mast cell tumors, nine of the 13 grade I tumors, 13 of the 19 grade II tumors, and 10 of the 15 grade III tumors showed no detectable or mild p27 immunoreactivity. In contrast, one of the 13 grade I tumors, 12 of the 19 grade II tumors, and 11 of the 15 grade III tumors showed moderate or marked p21 immunoreactivity. Nineteen of the 28 histiocytomas showed no detectable or mild p27 immunoreactivity, and 24 cases showed moderate or marked p21 immunoreactivity. These findings indicate that a loss or absence of p27 expression is an early pathogenic event in mast cell and histiocyte tumorigenesis and that p21 expression may be a marker of mast cell tumor progression and histiocytoma cell proliferation.

Mast Cell Tumors of the Gastrointestinal Tract in 39 Dogs

Mast cell tumors (MCTs) of gastrointestinal origin that had been surgically removed from 39 dogs were examined to evaluate their pathologic features. Miniature breeds, especially Maltese, were most frequently affected. The average age of affected dogs was 9.7 ± 2.6 years. No sex difference was apparent. The most frequently affected sites were in the upper digestive tract, and the prognosis was very poor. Grossly, the gastrointestinal wall was prominently thickened, and the lumen of the affected gut was usually narrowed. Microscopically, there was diffuse transmural invasion of round to pleomorphic tumor cells. Tumor cells had moderate to abundant cytoplasm, round to ovoid nuclei with scattered chromatin, and mitotic figures. Fibrous stroma was observed in about half of the tumors. There was variable infiltration of eosinophils. In all tumors, cytoplasmic granules showed weak metachromasia, but the number of granules was very small. Immunohistochemical staining for c-kit and mast cell tryptase was positive in 77% and 62% of tumors, respectively. All tumors were positive for at least two of these markers. Immunohistochemical staining for p53 was positive in 13% of the tumors. Reactivity for staining markers and p53 was unrelated to cell pleomorphism, vessel invasion, or survival time. Gastrointestinal MCTs have histologic and immunohistochemical features completely different from those of other primary or metastatic gastrointestinal tumors. The combination of immunostaining for mast cell tryptase and c-kit and histochemical staining for metachromasia appears to be a powerful tool for the diagnosis of gastrointestinal MCTs.

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.

Biological behavior of oral and perioral mast cell tumors in dogs: 44 cases (1996-2006)

OBJECTIVE

To describe clinical outcome of dogs with mast cell tumors (MCTs) arising from the oral mucosa, oral mucocutaneous junction, or perioral region of the muzzle and evaluate the potential role of the chemokine receptor type 7 (CCR7) in the biological behavior of these tumors.

DESIGN

Retrospective case series.

ANIMALS

44 dogs with MCTs of the oral mucosa (n=14), oral mucocutaneous junction (19), or perioral region of the muzzle (11).

PROCEDURES

Medical records were reviewed for information on signalment, regional metastasis, treatments, cause of death, and survival time. Twenty of the 44 cases had stored histologic samples available for immunohistochemical staining for CCR7

RESULTS

For all dogs, median survival time was 52 months. Twenty-six (59%) dogs had regional lymph node metastasis on admission. Median survival time for dogs with lymph node metastasis was 14 months, whereas median survival time was not reached for dogs without lymph node metastasis. Intensity of staining for CCR7 was not significantly associated with the presence of regional lymph node metastasis or survival time.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that in dogs with MCTs arising from the oral mucosa, oral mucocutaneous junction, or perioral region of the muzzle, the presence of regional lymph node metastasis at the time of diagnosis was a negative prognostic factor. However, prolonged survival times could be achieved with treatment. In addition, CCR7 expression in the primary tumor was not significantly associated with the presence of regional lymph node metastasis or survival time.

Avaliação da proliferação celular como indicador prognóstico para mastocitomas cutâneos caninos

Este estudo teve como objetivo avaliar o valor prognóstico de marcadores de proliferação celular em casos de mastocitomas cutâneos caninos. Vinte e três casos foram analisados quanto à expressão imuno-histoquímica de Ki67 e do Antígeno Nuclear de Proliferação Celular (PCNA), sendo subsequentemente acompanhados clinicamente. Observou-se que a expressão de Ki67 mantém relação negativa com a tradicional graduação histopatológica (p= 0,0418; p<0,05 entre os graus I e III), sendo um indicador confiável para o tempo de sobrevida pós-cirúrgica (p=0,0089). A imunoexpressão de PCNA, apesar de estar correlacionada à marcação por Ki67, não apresentou valores estatisticamente significantes na predição da mortalidade em função da doença e do tempo de sobrevida pós-cirúrgico. Os resultados obtidos confirmam que informações sobre a atividade proliferativa tumoral pela detecção imuno-histoquímica de Ki67 podem incrementar a classificação de mastocitomas cutâneos caninos quanto à malignidade.

Reactivity of p53 protein in canine transmissible venereal tumor

The expression of p53 protein was evaluated in canine transmissible venereal tumor (CTVT), as following: natural occurrence (n=8); resistant to chemotherapy (n=4); and allogeneic transplanted in progression (n=8), stable (n=8), and regression (n=8)stages. The collected specimens were submitted to GM1 immunohistochemical reaction. Results showed a mean percentage of immunomarked cells around 18.6% in CTVT of natural occurrence, 23.8% in CTVT resistant to chemotherapy, 22.9% in allogeneic transplanted CTVT in both progression and stable stages, and 35.8% in transplanted CTVT in regression stage. The results suggest that there is a functional abnormality in p53 gene and its products in the studied tumors; although, it is not possible to correlate the percentage of cells marked by p53 and a prognosis.

Evaluation of risk and clinical outcome of mast cell tumours in pug dogs

Mast cell tumours (MCT) are common in dogs and characterized by diverse biologic behaviour. Our objective was to evaluate the risk of MCT in pugs and to describe the clinical behaviour of MCT in this breed. Data obtained from the Veterinary Medicine Database demonstrate significantly increased frequency of MCT in pugs compared with other dogs (OR = 2.28, 95% CI = 1.81-2.86). The medical records for 25 purebred pugs with a histologic diagnosis of MCT were reviewed. Multiple cutaneous tumours were documented in 14 (56 %) of the dogs. Histologic review of 64 tumours from these dogs confirmed that most tumours (94%) were low to intermediate grade. Sixty-four per cent of these dogs are still living, while only three dogs (12%) have died due to mast cell disease. A median survival time has not been reached. The median follow-up time is 660 days from the diagnosis of the first MCT. We conclude that MCT in pugs are relatively benign, despite the presence of multiple cutaneous tumours in most cases. Multiple tumours in breeds with predisposition to MCT may indicate separate primaries rather than advanced stage disease.

Cutaneous mast cell tumour within a lipoma in a boxer

This report describes a case of a canine cutaneous grade I mast cell tumour which developed within a lipoma in the right axillar region of an 8-year-old male Boxer. Immunohistologically, the neoplastic mast cells were positive for serotonin, CD45 vimentin and p53, and negative for lysozyme, CD3 and CD79a expression. The proliferation index of the mast cell tumour based on the Ki-67 antigen was 6.1%. Between the benign neoplastic lipocytes and mastocytoma tumour cells intratumoural microvessels were detected by immunohistochemical staining using CD31 and claudin-5 as markers for vascular endothelium.

Canine mast cell tumours: a review of the pathogenesis, clinical features, pathology and treatment

Mast cells (MCs) are well known for their neoplastic transformation in solitary and multiple cutaneous mast cell tumours (MCTs), as well as visceral and systemic mastocytosis. Dogs have a unique risk of developing cutaneous MCTs, and they account for 7% to 21% of all canine skin tumours. The aetiology of canine MCTs is unknown but is probably multifactorial. This article reviews up-to-date knowledge on the pathogenesis, the clinical presentation, the clinical prognostic factors, the diagnostic workup including clinical staging, cytological findings, histological findings and the various grading systems which have been evaluated based on morphology, the assessment of proliferation markers and other factors such as vessel density. Furthermore, detailed information about current treatment protocols for canine cutaneous MCTs is provided.

Expression of proto-oncogene C-kit and correlation with morphological evaluations in canine cutaneous mast cell tumors

Canine cutaneous mast cell tumor (MCT) is very common disease in dogs, this is more aggressive than in other species. The biologic behavior of MCT is highly variable and a more accurate prognosis for these tumors needs to performed. The proto-oncogene c-kit is known to play a critical role in development and function of mast cells (MC). The aim of this study was to evaluate the expression of immunohistochemical pattern of c-kit in MCTs and to correlate these results with MC density (MCD) and intratumoral microvessel density (MVD). Our results confirm that a more aggressive biologic behavior of canine MCT is associated with the increased c-kit expression, further suggesting a new role for c-kit, as a useful marker, in diagnostic pathology and in tumor progression.

A Comprehensive Test System to Identify Suitable Antibodies Against p53 for Immunohistochemical Analysis of Canine Tissues

The tumour suppressor p53 is commonly detected in tissues of companion animals by means of antibodies raised against the human protein. The following three-step procedure was devised to test the suitability of such antibodies for immunohistochemistry on canine tissues. (1) Western blot and immunohistochemical analyses on bacterially expressed recombinant canine protein to assess human-to-canine cross-reactivity. (2) Immunohistochemistry of cultured, UVB-irradiated canine keratinocytes to evaluate suitability for detection of endogenous p53. (3) Immunohistochemistry on tissue arrays to further substantiate suitability of the antibodies on a panel of normal and neoplastic human and canine tissues. Five of six antibodies cross-reacted with recombinant canine p53. Three of these (PAb122, PAb240, CM-1) also immunolabelled stabilized wild type p53 in cell cultures and elicited a consistent, characteristic labelling pattern in a subset of tumours. However, two alternative batches of polyclonal antibody CM-1 failed to detect p53 in cell cultures, while showing a characteristic labelling pattern of a completely different subset of tumours and unspecific labelling of normal tissues. The test system described is well suited to the selection of antibodies for immunohistochemical p53 detection. The results emphasize the need to include appropriate controls, especially for polyclonal antibodies.

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.

Canine subcutaneous mast cell tumour: diagnosis and prognosis

The aim of this study was to characterize the pathology and clinical outcome of the subcutaneous variant of canine mast cell tumour. Fifty-three cases satisfying the inclusion criteria were selected from the pathology archive of the College of Veterinary Medicine, University of Tennessee. Referring veterinarians provided information on outcome. These dogs had a median age of 9 years (range 3-17 years). After characterizing tumours histologically, nuclear expression of proliferating cell nuclear antigen (PCNA) and Ki67 (MIB-1 clone) was determined immunohistochemically and mast cell origin was confirmed with c-Kit staining. Counts of argyrophilic nucleolar organizer regions (AgNOR) were determined by silver staining. Nuclear labelling was counted in 100 tumour cells. Margins were recorded as incomplete in 66% of dogs, and metastases occurred in 6% of dogs. The estimated minimum mean survival time from date of diagnosis was 1199 days, ranging from 55 to >1780 days. The median scores from immunohistochemical labelling were PCNA 0.05 and Ki67 0.03 per 100 tumour cells. The median score for AgNOR staining was 1.25 per 100 tumour cells. The patterns of c-Kit expression included membranous labelling in 20 tumours, stippled cytoplasmic labelling in 23 tumours and diffuse cytoplasmic labelling in 10 tumours. Age (r=-0.61, P=0.14) and AgNOR score (r=-0.58, P=0.17) had moderate, but non-significant, negative associations with survival. PCNA (r=-0.32, P=0.47), Ki67 (r=-0.22, P=0.64) and c-Kit immunolabelling was not associated with survival. The subcutaneous variant of canine mast cell tumour is distinct in having features of intermediate histological grade and extended mean survival times, suggesting a slightly better long-term prognosis than for higher grade dermal variants. Expression of nuclear proliferation markers is not associated with outcome.

Immunohistochemical expression of Mdm2 and p53 in canine cutaneous mast cell tumours

The objective of this study was to evaluate by immunohistochemical means nuclear reactivity for Mdm2 and p53 proteins in 71 canine cutaneous mast cell tumours. Detectable reactivity for Mdm2 was observed in 17 of 23 grade I tumours, 19 of 27 grade II tumours, and 14 of 21 grade III tumours, the grading method used was that by Patnaik et al. [Vet. Pathol., vol. 21, 1984, p. 469]. Increased reactivity for Mdm2 was detected in grade III tumours compared with grade I tumours. In contrast to Mdm2, detectable reactivity for p53 was observed in 17 tumours. Of 39 cases with moderate or marked Mdm2, 34 showed mild or no detectable p53, although only five showed moderate or marked p53. The results suggest that Mdm2 overexpression plays a crucial role in canine mast cell tumorigenesis and is consistent with the histologic grade, and its expression may be induced without p53 overexpression.

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.

Prognostic and predictive markers in canine tumours: rationale and relevance. A review

Cancer is one of the most common causes of death in dogs. The availability of multiple treatment modalities and novel therapeutic targets make the correct diagnosis, prognostic stratification, and the identification of treatment effect predictive factors an issue of major debate in cancer management. Selection of high and low risk patients and the type of systemic or local treatment is important in cancer management. The search for better prognostic markers and predictive factors is now focused on the molecular mechanisms which underlie tumour behaviour, such as altered cell cycle progression, proliferation, apoptosis, and angiogenesis. The ultimate goal is to identify reliable markers that can accurately diagnose and stage a tumour and predict tumour's clinical behaviour, prognosis and response to therapy. In this review, the current state of prognostication in canine tumours and promising new molecular markers are discussed. The markers are allocated to four groups according to their function: (i) proliferation markers, (ii) apoptosis, (iii) extracellular matrix and cell adhesion molecules, (iv) angiogenesis and (v) cell cycle regulators. Clinicopathological factors and histopathological grading remain the most practical parameters in decision-making. Although experimental research has shown that molecular markers have a good potential to be used as diagnostic, prognostic or predictive markers in canine tumours, insufficient evidence exists on their efficacy for routine use in veterinary oncology.

Nucleomorphometric Analysis of Canine Cutaneous Mast Cell Tumours

Thirty-five canine cutaneous mast cell tumours (CCMCTs) were analysed by computerized nuclear morphometry. In each case, the nuclei of at least 100 neoplastic cells were measured, and the mean nuclear area (MNA), mean nuclear perimeter (MNP) and mean nuclear form factor (FF) were calculated. Significant differences in respect of MNA and MNP occurred between tumours of grades I and III and between those of grades II and III (P<0.01) but not between tumours of grades I and II (P>0.01). No significant differences in respect of FF were observed between tumours of different grades. The results obtained indicate that nuclear morphometric analysis may assist in the grading of CMCTs.

Outcome of dogs with mast cell tumors in the inguinal or perineal region versus other cutaneous locations: 124 cases (1990?2001)

OBJECTIVE

To compare clinical outcome of dogs with cutaneous mast cell tumors (MCTs) in the inguinal or perineal region with outcome for dogs with MCTs in other cutaneous locations.

DESIGN

Retrospective study.

ANIMALS

37 dogs with MCTs in the inguinal or perineal region and 87 dogs with MCTs in other cutaneous locations.

PROCEDURE

Information obtained from the medical records included sex, breed, age, histologic grade of all tumors, number and location of all tumors, tumor size (ie, diameter of the tumor), completeness of surgical excision, treatments administered in addition to surgery, and outcome. In all dogs, the primary treatment consisted of surgical excision.

RESULTS

Disease-free interval and survival time for dogs with MCTs in the inguinal or perineal region were not significantly different from values for dogs with MCTs in other cutaneous locations. Dogs with incompletely excised tumors, dogs with grade III tumors, and dogs that received systemic treatment were 2, 2.5, and 4 times as likely, respectively, to have a relapse. Factors significantly associated with a shorter survival time were age > 8 years, metastatic disease at the time of initial diagnosis, and tumor relapse.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of the present study suggest that dogs with MCTs in the inguinal or perineal region do not have a worse prognosis in regard to disease-free interval or survival time than do dogs with MCTs in other cutaneous locations. Treatment recommendations for dogs with cutaneous MCTs should be based on confirmed predictors of biological behavior, such as histologic grade and clinical stage.

Mast cells and canine mast cell tumours. A review

This article reviews the literature on mast cells and tumours derived from mast cells in the dog. Mast cells play a central role in inflammatory and immune reactions. Mast cells, normal and neoplastic, contain and release important biologically active substances: heparin, histamine, eosinophilic chemotactic factor and proteolytic enzymes. Mast cell tumours occur in the dog, particularly in the boxer and related breeds, in the skin and less frequently in the intestines. Cytology usually provides an accurate diagnosis, but histological examination adds further information concerning the histologic grade and the completeness of surgical therapy. Cutaneous mast cell tumours should be regarded as potentially malignant and therefore be removed widely (3 cm. margin). Local recurrence, regional and distant metastases together with paraneoplastic disorders may cause the death of the pet. Histologic grading (2 or 3 grades) and clinical staging together with kinetic parameters and breed (boxers have relatively benign tumours) are important prognostic parameters. Based on prognostic criteria, surgical treatment should be completed with adjuvant radiotherapy, corticosteroids and eventually with combined chemotherapy. A novel, promising therapy is the application of the receptor kinase inhibitor. The study of the pathogenesis of mast cell tumours received new impetus by the finding of mutations, deletions and duplications, in exons 11 and 12 of the C-kit oncogene. Further study of physiological and oncological aspects of mast cells are favoured by the availability of mast cells isolated from spontaneous mast cell tumours and of cultured cell lines.

Canine Lymphomas: a Morphological and Immunohistochemical Study of 55 Cases, with Observations on p53 Immunoexpression

The purpose was to determine the immunophenotype of canine lymphomas (CLs) classified according to the WHO nomenclature for domestic animals, and to relate these findings to the immunoexpression of p53 protein. Lymphomas were immunophenotyped with antibodies to CD79a, CD3, and p53 protein, suitable for paraffin wax-embedded tissue sections. Of 55 cases, 40 (72.7%) were of the B-cell phenotype, 12 (21.8%) of the T-cell phenotype, and three (5.4%) were non-B-non-T lymphomas. Of the 40 B-cell lymphomas, 31 were of the large B-cell type, six were lymphoplasmacytic, one lymphocytic, one follicular (grade II) and one unclassified low-grade. One of the peripheral T-cell lymphomas was morphologically consistent with anaplastic large cell lymphoma. Immunolabelling for p53 occurred in 24 B-cell and seven T-cell lymphomas. Lymphomas with high grade histology showed a significantly increased frequency of p53 positivity (P = 0.01). Positivity for p53 (more than 10% positive cells) tended to be associated with the T-cell phenotype (P = 0.06). Mean patient age was significantly higher in p53-positive cases (P = 0.02). These data are comparable with findings in human lymphomas.

Efficacy of radiation therapy for incompletely resected grade-III mast cell tumors in dogs: 31 cases (1987–1998)

OBJECTIVE

To determine the efficacy (durations of remission and survival) of an alternating-day radiation protocol for incompletely excised histologic grade-III solitary mast cell tumors (MCTs) in dogs.

DESIGN

Retrospective study.

ANIMALS

31 dogs.

PROCEDURE

Radiation (52 Gy in an 18-fraction alternating-day protocol) was delivered to an area bordered by margins > or = 3 cm around the surgical scar and to the associated local-regional lymph nodes. Dogs were not given chemotherapeutic agents concurrently or after radiation. Information on signalment, duration of remission, and survival time was obtained from medical records.

RESULTS

Median and mean durations of remission were 27.7 and 17.0 months, respectively (range, 1 to 47 months). Median and mean durations of survival were 28 and 20 months, respectively (range, 3 to 52 months). Dogs with tumors located on the skin of the pinna, perineum, and prepuce had a median duration of remission greater than dogs with tumors located at other sites (27.7 and 14.4 months, respectively). Dogs with tumors < or = 3 cm in maximum diameter before surgery survived longer than dogs with tumors > 3 cm (31 and 24 months, respectively). The remission rate was 65% and survival rate was 71% at 1 year after treatment. Sixteen dogs that were euthanatized had complications associated with local-regional tumor progression. Systemic metastases to liver, spleen, intestine, and bone marrow were detected in 1 dog.

CONCLUSIONS AND CLINICAL RELEVANCE

Without further treatment, incompletely excised grade-III mast cell tumors have high local-regional recurrence; local-regional treatment with radiation may effectively be used to manage many such tumors.

Biologic behavior and prognostic factors for mast cell tumors of the canine muzzle: 24 cases (1990-2001)

The medical records of 24 dogs with histologically confirmed mast cell tumors (MCT) of the muzzle were retrospectively evaluated to determine their biologic behavior and prognostic factors. Information on signalment, tumor grade and stage, treatment methods, and pattern of and time to failure and death was obtained from the medical record. Twenty-three dogs were treated with combinations of radiotherapy, surgery, and chemotherapy; 1 dog received no treatment. There were 2 Grade 1, 15 Grade 11, and 7 Grade III tumors. Tumors were stage 0 (n = 8), stage 1 (5), stage 2 (6), stage 3 (4), and stage 4 (1). Mean and median survival times of treated dogs were 36 and 30 months, respectively. Prognostic factors affecting survival time included tumor grade and presence of metastasis at diagnosis. Dogs with Grade I and II tumors survived longer than dogs with Grade III tumors. Variables, including sex, age, gross versus microscopic disease, and treatment type were not found to affect survival. Local control rate was 75% at 1 year and 50% at 3 years. Tumor grade was the only variable found to affect local control. Dogs with Grade I tumors had longer disease-free intervals than those with Grade II tumors, and dogs with Grade II tumors had longer disease-free intervals than dogs with Grade III tumors. Eight of 9 dogs dying of MCT had local or regional disease progression. Muzzle MCT a rebiologically aggressive tumors with higher regional metastatic rates than previously reported for MCT in other sites.

Clinical and pathologic relevance of p53 index in canine osseous tumors

The clinicopathologic value of the immunohistochemical (IHC) expression of p53 protein was evaluated in 167 canine osseous tumors. p53 staining frequency and intensity in tumor cells was expressed as a p53 index. p53 index was significantly higher in osteosarcomas than in other sarcomas, chondrosarcoma, multilobular tumor of bone, and tumors initially misdiagnosed as osteosarcomas as well as in appendicular versus axial and in distal versus proximal osteosarcomas. A strong correlation is demonstrated between the p53 index and a range of clinicopathologic parameters in osteosarcoma, including the tumor site, histologic grade and score, mitotic index, degree of tumor necrosis, and pleomorphism. Chondroblastic osteosarcomas had significantly higher and telangiectatic osteosarcomas significantly lower p53 index than did osteosarcomas belonging to other histopathologic subtypes, a fact that tends to reinforce the perception of these osteosarcomas as distinct clinicopathologic entities. Entire males had higher p53 index than did neutered males. p53 index was higher in Rottweilers than in Great Danes and Terriers, confirming breed susceptibilities to osteosarcoma. p53 index showed no association with age, primary or secondary site status, or the presence of metastases or other tumor types. Biopsy samples had a higher p53 index than did postmortem samples, either because of differences in sample processing or the possibility that p53 overexpression is more evident at the earlier stages of osteosarcoma pathogenesis, presumably represented by the biopsy material. IHC examination for p53 and the derived index has the potential to be used as an additional diagnostic tool and prognostic indicator for osseous tumors.

Mast cell tumors in the dog

The most common skin tumor in dogs is the mast cell tumor (MCT), with an incidence of close to 20% in the canine population. MCTs range from relatively benign to extremely aggressive, leading to metastasis and eventual death from systemic disease. Although surgical removal with or without radiation therapy may cure most patients with low-grade MCTs, there are no effective treatments for dogs with aggressive high-grade MCTs. This article reviews the current understanding of MCT biology with regard to diagnosis, staging, identification of prognostic indicators, and appropriate treatment planning.

Morphometry of canine cutaneous mast cell tumors

Twenty-four canine cutaneous nodules, diagnosed as mast cell tumors by fine-needle aspiration biopsy and confirmed by histopathologic analysis by staining with hematoxylin and eosin (HE) and toluidine blue, were analyzed by computerized nuclear morphometry on panoptic- and HE-stained cytopathology slides. Two hundred nuclei per lesion were examined. The morphometric parameters investigated were nuclear area, mean diameter, perimeter, regularity factor, and ellipticity factor. 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. Nuclear morphometric results were then compared with histopathologic grades. Values of nuclear area, mean diameter, and perimeter increased with increase in histopathologic grade, but statistical analysis revealed significant differences only between grades II and III and between grades I and III when HE was used (P < 0.01) and between grades I and III with panoptic stain (P < 0.05). The ellipticity factor and regularity factor did not reveal significant differences between histopathologic grades. The results indicate that nuclear morphometric analysis, in combination with the rapid and inexpensive cytopathology technique, can help in mast cell tumor grading, thus contributing to the establishment of a more precise prognosis and treatment.