C-kit expression in canine mucosal melanomas

The c-kit receptor is responsible for transmission of promigration signals to melanocytes; its downregulation may be involved in malignant progression of human melanocytic neoplasms. Expression of this receptor has not been examined in normal or neoplastic melanocytes from dogs. In this study, 14 benign dermal and 61 malignant mucosal melanocytic tumors were examined for c-kit (KIT) expression. Sites of the mucosal melanomas were gingiva (not further specified; n = 30), buccal gingiva (n = 6), soft palate (n = 4), hard palate (n = 5), tongue (n = 7), lip (n = 6), and conjunctiva (n = 3). Melan A was expressed in all 14 dermal melanocytomas and in 59 of 61 (96.7%) tumors from oral or conjunctival mucosa, confirming melanocytic origin. C-kit receptor expression was strong and diffuse throughout the cytoplasm in all 14 dermal melanocytomas and was identified in basilar mucosal melanocytes over submucosal neoplasms (27 of 61, 44.3%), junctional (neoplastic) melanocytes (17 of 61, 27.9%), and, less commonly, neoplastic melanocytes of the subepithelial tumors (6 of 61, 9.8%). KIT expression anywhere within the resected melanomas correlated with significantly longer survival. These results suggest that c-kit receptor expression may be altered in canine melanomas and may have potential as a prognostic indicator for mucosal melanomas.     

Canine cutaneous neoplasms: prevalence and influence of age, sex and site on the presence and potential malignancy of cutaneous neoplasms in dogs from Zimbabwe

Histopathological examination was performed on cutaneous biopsies from 900 dogs with skin lesions from Zimbabwe, collected from 1996 to 2000. Clinical data were collected from medical records. Sixty per cent (540/900) of the cases were tumours and 40% (360/900) were non-neoplastic inflammatory or degenerative diseases. Thirty different histological types of tumour were diagnosed. The prevalence of epithelial, mesenchymal, lymphohistiocytic and melanocytic tumours was 39.4%, 44.4%, 7.4% and 8.7%, respectively. The 10 most common tumours, comprising 73.7% of all cutaneous neoplasms, were mast cell tumours, squamous cell carcinomas, perianal gland adenomas, lymphomas, benign melanomas, haemangiosarcomas, sebaceous gland adenomas, fibrosarcomas, lipomas and malignant melanomas. The prevalence of various neoplasms, age of affected dogs and sites of occurrence were similar to surveys in other countries, except that in Zimbabwe there was a greater prevalence of lymphomas and of tumours associated with increased exposure to ultraviolet light (squamous cell carcinomas, haemangiosarcomas and melanomas). For all classes of tumours the sex of the dog did not have any significant influence on the likelihood of developing a tumour. For a dog diagnosed with a tumour located on the trunk, the tumour was significantly more likely to be an epithelial tumour than a non-epithelial tumour The occurrence of melanocytic tumours on the trunk was significantly lower than at other sites. Lymphohistiocytic tumours were 10 times more likely to occur at multiple locations as opposed to single locations.     

Morphology and behavior of primary ocular melanomas in 91 dogs

Primary ocular melanocytic neoplasms from 91 dogs were divided into two groups by histologic criteria. Seventy-five were benign and composed of spindle-shaped and large polyhedral melanocytes similar to those of human ocular melanocytomas. Fifty-nine of these originated in the uvea where most resulted in uveitis, glaucoma, or hyphema prior to enucleation. None metastasized. Nineteen melanocytomas were limbal tumors. None metastasized, but three of nine incompletely excised tumors were found within the anterior chamber 2 to 3 years after the initial removal. Sixteen uveal melanocytic neoplasms were histologically malignant. Three had confirmed metastases, all within 3 months of enucleation. Cell type or pattern of growth within the globe were not predictive of biologic behavior. Our data suggest that the mitotic index is the best criterion for histologic identification of ocular melanomas with high metastatic potential. We propose that the classification of primary ocular melanomas be simplified to include only two categories: melanocytoma (benign) and melanoma (potentially malignant). Further behavioral data may justify a grading scheme for melanomas based upon mitotic index.     

Fascin‐1 expression in canine cutaneous and oral melanocytic tumours

Fascin‐1 expression was examined in 9 cutaneous melanocytomas and 47 oral melanomas. The cases were scored on the basis of extent and intensity of staining, and combined scores were calculated. Fascin‐1 expression was observed in 5/9 (56%) melanocytomas and 46/47 (98%) melanomas. The combined score for fascin‐1 was significantly greater in stage III/IV melanomas than in stage I/II melanomas (P < 0.05). In addition, strong fascin‐1 staining was associated with a significantly shortened survival time (P < 0.05). The results of this study suggest that fascin‐1 overexpression correlates with the malignancy of canine melanoma and has the potential to be a new immunohistochemical marker to predict the clinical course of canine melanoma. In addition, targeted therapy for fascin‐1 may represent a new strategy for the treatment of canine melanoma.     

p53 expression and apoptosis in melanomas of dogs and cats

Twenty-seven melanocytic tumours from 20 dogs and four cats were examined for p53 expression and apoptosis. They included tumours that were histologically classified as benign (BM), primary malignant (PMM) and metastatic malignant melanomas (MMM). For all cases clinical follow-up was available. p53 expression was examined immunohistochemically using different monoclonal and polyclonal antibodies. Apoptosis was detected using the TUNEL technique. The tissue sections were analysed using a quantitative image analysing system. A p53 index (p53I) and an apoptotic index (AI) were determined. p53 over-expression was found infrequently in these canine and feline melanocytic tumours. Apoptosis was observed in some of the malignant tumours. In one feline case of malignant melanoma, p53 accumulation together with apoptosis was seen in three metastases but not in the primary tumour. p53I and AI were not significantly correlated with survival. These results are similar to those reported for human cutaneous melanomas.     

Immunohistochemical expression of MDR1‐Pgp 170 in canine cutaneous and oral melanomas: pattern of expression and association with tumour location and phenotype

Canine melanoma (CMM) more commonly affects the oral mucosa and the cutis. CMM shares several features with human melanomas (HMM), included resistance to a broad variety of antineoplastic chemotherapy agents. P‐glycoprotein 1 (Pgp) expression is a well‐recognized feature of multi‐drug resistance and the purpose of this study was to investigate its expression in treatment naïve CMM. We also investigated Pgp association with tumour location and histological features. Histology records of CMM were retrieved, including patients from 2012–2014. Twenty‐five cases of CMM were included in this study. Results revealed that Pgp is expressed in CMM and oral tumours were more likely to have a membranous Pgp expression (100%) than cutaneous tumours (66.6%) (P = 0.010). Cytoplasmic and nuclear Pgp expression could also be identified. Results of this study bring useful data that help in understanding one of the possible mechanisms responsible of intrinsic chemotherapy resistance in canine CMM.     

Prognosis after surgical excision of canine melanomas.

One hundred and thirty-four dogs from which melanomas had been excised were studied until death or for at least 2 years after surgery. Seven of 49 (14%) intraoral and lip tumours and 52 of 85 (61%) skin tumours were histologically benign; in spite of this, three of seven (43%) "benign" oral and four of 52 (8%) "benign" skin lesions led to the eventual death of the host. Thirty eight of 42 (90%) dogs with a histologically malignant melanoma of the lip or oral cavity died because of the tumour but only 15 of 33 (45%) with malignant skin melanomas died. Six of 59 (10%) dogs with a tumour of mitotic index 2 or less died from the tumour 2 years after surgery compared to 19 of 26 (73%) dogs having a tumour with a mitotic index of 3 or more.     

A matched observational study of canine survival with primary intraocular melanocytic neoplasia

A retrospective histopathologic study was performed to evaluate the effect of primary intraocular melanocytic neoplasia on canine survival. Tumor size, location within the globe, extent of infiltration, and mitotic index were analyzed for their potential to predict survival. A total of 244 cases of dogs with melanocytic tumors submitted to the Comparative Ocular Pathology Laboratory of Wisconsin from 1988 to 1998 were evaluated. Histopathologic criteria (mitotic index, cytologic features of anaplasia) were used to differentiate 188 benign melanocytomas from 56 malignant melanomas. Signalment evaluation of age, sex, and breed revealed similarities in both tumor populations, with the majority of tumors discovered in 9-year-old, female/spayed, mixed-breed dogs. A greater percentage of left eyes (66%) vs. right eyes (47%) was found in the melanoma population, but an equal distribution was found in the melanocytoma population (48% and 52%, respectively). The majority of tumors arose from the anterior uveal tract (79% in the melanocytoma and 95% in the malignant melanoma populations). The German Shepherd breed was predisposed in the limbal distribution. At the time of enucleation, most tumors had invaded the sclera, but did not show extrascleral extension (51% in the melanocytoma and 61% in the malignant melanoma populations). Survival analysis showed a significant difference in survival between control and malignant melanoma populations ( P  = 0.0081) and was suggestive of a difference between the melanocytoma and melanoma populations ( P  = 0.031). Tumor extension, tumor size, and mitotic index were not found to be reliable predictors of survival.     

Prognostic value of somatic focal amplifications on chromosome 30 in canine oral melanoma

Canine oral melanoma is the first malignancy of the oral cavity in dogs and is characterized by a local invasiveness and a high metastatic propensity. A better knowledge of genetic alterations is expected to improve management of this tumour. Copy number alterations are known characteristics of mucosal melanomas both in dogs and humans. The goal of this study was to explore the prognostic value of somatic focal amplifications on chromosomes (Canis Familiaris [CFA]) 10 and 30 in canine oral melanoma. The cohort included 73 dogs with oral melanoma confirmed by histology, removed surgically without adjuvant therapy and with a minimal follow‐up of 6 months. Epidemiological, clinical and histological data were collected and quantitative‐PCR were performed on formalin‐fixed paraffin‐embedded (FFPE) samples to identify specific focal amplifications. The 73 dogs included in the study had a median survival time of 220 days. Focal amplifications on CFA 10 and 30 were recurrent (49.3% and 50.7% of cases, respectively) and CFA 30 amplification was significantly associated with the amelanotic phenotype (P = .046) and high mitotic index (MI; P = .0039). CFA 30 amplification was also linked to poor prognosis (P = .0005). Other negative prognostic factors included gingiva location (P = .003), lymphadenomegaly (P = .026), tumour ulceration at diagnosis (P = .003), MI superior to 6 mitoses over 10 fields (P = .001) and amelanotic tumour (P = .029). In multivariate analyses using Cox proportional hazards regression, CFA 30 amplification (Hazard ratio [HR] = 2.08; P = .011), tumour location (HR = 2.20; P = .005) and histological pigmentation (HR = 1.87; P = .036) were significantly associated with shorter survival time. Focal amplification of CFA 30 is linked to an aggressive subset and constitutes a new prognostic factor.     

Immunohistochemical characterization of tumor cells and inflammatory infiltrate associated with cutaneous melanocytic tumors of Duroc and Iberian swine

The immunophenotype of tumor cells and inflammatory infiltrate associated with cutaneous melanocytic lesions (29 melanocytomas, two malignant melanomas, and 23 residual lesions) from 54 adult Iberian and Iberian x Duroc pigs were examined using a panel of nine antibodies. All neoplastic cells were vimentin+, cytokeratin-, and alpha-1-antitrypsin- and the majority were S100+, whereas all pigmented macrophages were vimentin+, cytokeratin-, and S100- and most expressed alpha-1-antitrypsin. Regressing tumors were characterized by zones with low density of neoplastic cells accompanied by heavy infiltration of CD3+ T lymphocytes, whereas zones with high density of neoplastic cells showed very low numbers of CD3+ T lymphocytes. The infiltrate of CD79a+ B cells and IgG, IgM, and IgA plasma cells was low. The majority of lymphocytes of the peri- and intratumoral infiltrate were major histocompatibility complex class II+, but neoplastic cells did not express class II antigen. The 17 residual lesions examined were composed of macrophages containing abundant melanin pigment and low to moderate numbers of CD3+ T lymphocytes. The results of the present study suggest that the local cellular immune response plays a crucial role in the host response that induces regression of cutaneous melanomas and melanocytomas of the Iberian and crossbred Iberian x Duroc pigs.     

Canine mammary gland tumours; a histological continuum from benign to malignant; clinical and histopathological evidence*

This study describes the clinical and histopathological findings in dogs with mammary gland tumours, and compares the histopathological and clinical evidence consistent with progression from benign to malignant to human breast cancer epidemiology. Clinical and histopathological data on 90 female dogs with 236 tumours was included. Dogs with malignant tumours were significantly older than dogs with benign tumours (9.5 versus 8.5 years), P = 0.009. Malignant tumours were significantly larger than benign tumours (4.7 versus 2.1 cm), P = 0.0002. Sixty‐six percent had more than one tumour, and evidence of histological progression was noted with increasing tumour size. Dogs with malignant tumours were significantly more likely to develop new primary tumours than dogs with benign tumours, P = 0.015. These findings suggest that canine mammary tumours progress from benign to malignant; malignant tumours may be the end stage of a histological continuum with clinical and histopathological similarities to human breast carcinogenesis.     

Correlation of quantified contrast-enhanced power Doppler ultrasonography with immunofluorescent analysis of microvessel density in spontaneous canine tumours

Conventionally, tumour vascularity is assessed invasively by immunofluorescent analysis. Quantified contrast-enhanced power Doppler ultrasound has been used to measure tumour angiogenesis non-invasively in humans and experimental animals. The purpose of this study was to correlate quantified contrast-enhanced power Doppler ultrasound with immunofluorescent results in 45 spontaneous canine tumours. With power Doppler, mean vascularity was high in squamous cell carcinomas, moderate in malignant oral melanomas and low in sarcomas. There was high mean vascularity in squamous cell carcinomas and low mean vascularity in sarcomas and malignant oral melanomas. Although Doppler parameters correlated moderately with microvascular density for all tumours (P=0.004, r=0.4), they did not correlate within histology groups. These analyses show that vascularity differs among canine tumour histology groups. However, dependent on the method used, measurement of tumour vascularity can provide different biological information.     

Cytogenetic analysis of three oropharyngeal malignant melanomas in dogs.

Three cases of histologically confirmed oropharyngeal malignant melanomas in dogs are presented including clinical examinations and cytogenetic analysis. Case one showed a hyperdiploid karyotype. Case two, a recurrent tumour, had a highly hypodiploid karyotype with supernumerary meta- and submetacentric chromosomes in all metaphases analysed. In the third case, a clonal fusion of chromosome 1 and 25 was observed. Comparing these results with another case of canine cutaneous melanoma as well as with human malignant melanomas reported in the literature, these tumours obviously often show cytogenetic aberrations like aneuploidy and centric fusions.     

Perianal malignant melanoma in a dog

Melanocytic tumors are relatively common in dogs and most often occur in the oral cavity, lip, skin, digit, and eye. There are notable differences in the behavior of these tumors, depending on their anatomical location. The majority of oral melanomas and two-thirds of melanomas arising from the digit are malignant, whereas most of melanomas originating from the haired skin are benign. The anus and perianal areas are very uncommon sites for melanocytic tumors in domestic animals except horses, and most of those tumors in horses are malignant. To our knowledge, perianal malignant melanoma has not been reported in the dog and its prognosis is unknown.     

PCNA and grade in 13 canine oral squamous cell carcinomas: association with prognosis

This study evaluated the prognosis factors of age, tumour size, anatomic location, histological grade and proliferating cell nuclear antigen (PCNA) expression in 13 dogs with oral squamous cell carcinoma (OSCC) with bone invasion and without signs of lymph node or distant metastasis. All animals were treated with radical excision performed with at least 1 cm margin, based on computed tomography images. In the 2‐year follow‐up, median disease‐free survival was 138 days for dogs with grade 3 tumours and was not reached for those with grade 2 tumours. Grade 3 tumours and PCNA labelling index ≥65% were related with a shorter disease‐free survival time and consequently poor prognosis (p = 0.003 and p = 0.034, respectively). Mean PCNA labelling index was significantly higher in recurrent cases (p = 0.011). Histological grade and PCNA expression may be important prognosis factors in canine OSCC.     

Changes in C-reactive protein and haptoglobin in dogs with lymphatic neoplasia

Acute phase proteins (APP) are regarded as a useful diagnostic tool in humans with lymphomas, leukaemias and multiple myeloma. C-reactive protein (CRP) and haptoglobin concentrations were measured in dogs with malignant multicentric (high grade) lymphoma (n=16), acute lymphoblastic leukaemia (ALL) (n=11), chronic lymphocytic leukaemia (CLL) (n=7) and multiple myeloma (n=8). Twenty-five healthy dogs served as controls. Measurements of the CRP plasma concentration were performed using a commercial ELISA and haptoglobin was measured with an assay based on its haemoglobin binding capacity. Global group comparisons using Kruskal-Wallis-test revealed significant group differences for both APPs (P<0.0001). Median CRP concentrations were increased in all groups with neoplastic lymphatic disorders (lymphoma: 37.2mg/L, ALL: 47.8mg/L, CLL: 35.5mg/L, myeloma: 17.6mg/L) compared to controls (1.67mg/L; P<0.001). Compared to the healthy controls (median=0.59g/L), haptoglobin was especially increased in dogs with ALL (6.8g/L, P<0.0001) followed by dogs with malignant lymphoma (3.8g/L, P<0.0001), CLL (3.2g/L, P=0.0008), and multiple myeloma (3.0g/L, P=0.0163). For both APPs, a wide range of values was found in all patient groups. The results indicate that particularly severe and acute lymphatic neoplasia, such as high grade lymphoma and ALL, cause significant acute phase reactions in dogs and must be included in the differential diagnoses of increased blood levels of these APPs.     

Relationships between the histological grade of cutaneous mast cell tumours in dogs, their survival and the efficacy of surgical resection

The histological grade of 340 cutaneous mast cell tumours derived from 280 dogs was determined by an established histological grading system; 87 of the tumours (26 per cent) were well differentiated, 199 (59 per cent) were intermediately differentiated and 54 (16 per cent) were poorly differentiated. The one-year survival rates for the dogs with tumours of these three grades were significantly different (P = 0.0001), being 100 per cent, 92 per cent and 46 per cent, respectively. The median survival time for the dogs with poorly differentiated tumours was 278 days, significantly shorter than that for the dogs with either intermediately or well-differentiated tumours, which were both over 1300 days. Regrowth of the tumours was identified in 10 (19 per cent) of the dogs with poorly differentiated tumours, 12 (6 per cent) of the dogs with intermediately differentiated tumours and one of the dogs with well-differentiated tumours; only three of the tumours which regrew had initially had complete margins. The results suggest that wide surgical margins are not a prerequisite for a successful long-term outcome in dogs with well-differentiated cutaneous mast cell tumours.     

An osteoid variant of cutaneous melanoma in a dog detected by S100 and melan a markers

Osteoid malignant melanoma is a rare type of melanoma described in humans and dogs with some areas of bone differentiation. In this tumour, the origin of the bone matrix remains unclear. We report one case of this variant with, for the first time, a cutaneous origin in a dog. Malignant melanomas are aggressive tumours. Amelanotic tumours are sometimes difficult to recognize as they require immunohistochemical evaluation for an adequate diagnosis and we have used anti-vimentin, S100, and melan A antibodies for identification. Melan A is less sensitive but more specific than S100 in identifying amelanotic melanomas. This tumour was positive for vimentin, S100 and melan A, including the areas of osteoid. These results suggest osteoid differentiation of tumour cells rather than induced stromal metaplasia.