Histomorphological and immunohistochemical characterization of 172 cutaneous round cell tumours in dogs

Chemoresistance Cytological Score for Canine Transmissible Venereal Tumour: A Proposed System of Predicting Vincristine Resistance

Canine transmissible venereal tumour (CTVT) is a common diagnosis in many low-income countries, and managing its chemoresistant cases can be challenging within the conventional vincristine sulfate chemotherapy protocol. Also, predictive markers of chemoresistance for this tumour remain unidentified. This study aimed to evaluate CTVT cytological characteristics to develop a predictive cytological scoring system for vincristine sulfate resistance. For this purpose, 40 cases were retrospectively analysed based on their clinical aspects and response to vincristine chemotherapy. First, cytological preparations underwent a double-blind assessment to evaluate a modified cytomorphological classification. This classification, an adaptation of a previously published system, categorised tumours based on cell shape (plasmacytic versus lymphocytic), but no association with chemoresistance was found (p = 0.083). Subsequently, a novel cytology scoring system was developed and tested to identify cases potentially associated with chemoresistance. This system was based on three criteria: anisokaryosis, mitotic count, and the presence of binucleated cells. Malignancy criteria, evaluated in 5 hotspots, were inversely associated with chemoresistance (p = 0.001), predicted by low anisokaryosis, a mitotic count of ≤ 6 in a 2.37 mm2 area, and no binucleated cells. This study introduces a novel cytology scoring system for CTVTs, designed to serve as a predictive tool for vincristine treatment response. This system has the potential to aid practitioners in clinical decision-making. However, further studies are required to validate its reliability and applicability.

Immunohistochemical expression of vimentin, E-cadherin, and CD45 in natural cases of canine cutaneous round tumors

Round cell tumors are common cutaneous lesions in dogs, with increased occurrence percentages among different skin tumors. This study aimed to investigate the frequency as well as gross and pathological characteristics of round cell tumors in natural cases of tumorous dogs in relation to breed, sex, and age. Moreover, it aimed to evaluate the immunohistochemical expression of a panel of immunohistochemical stains, including vimentin, E-cadherin, and cluster of differentiation (CD45) as an adjunct technique for the differential diagnosis of cutaneous round cell neoplasm. Data were collected from 64 dogs of both sexes (36 females and 28 males), various breeds, and different ages (8 months to 7 years). The histopathological nature of neoplastic growth was reported, and neoplasm prevalence was classified using age, sex, breed, and site on the body. We observed 48 cases of transmissible venereal tumors, 12 cutaneous histiocytomas, and 4 histiocytic sarcoma. Immunohistochemical characterization revealed an intense positive immunoreactivity for vimentin in transmissible venereal tumor cells and moderate positive immunoreactivity for E-cadherin and CD45 in cutaneous histiocytoma and histiocytic sarcoma cells. In conclusion, the canine transmissible venereal tumor was the most frequent form of round cell tumor; thus, a definitive cutaneous neoplasm diagnosis should be based on histopathological morphology and immunohistochemical findings.

Epidemiological study of canine transmissible venereal tumor (CTVT) in Brazil, 2000-2020

Canine transmissible venereal tumor (CTVT) is a contagious neoplasm, mainly transmitted through coitus. This round cell mesenchymal tumor is common in Brazil, often located in the genitalia although extragenital presentations may also occur, such as cutaneous, oral, and nasal forms. The objective of this study was to perform an epidemiological analysis of CTVT from published data in the recent academic literature to systematically demonstrate the distribution of CTVT in Brazil, identify the frequency of this neoplasm and its main diagnostic tests, and characterize its main clinical manifestations in Brazil. For such purpose, it was analyzed the scientific publications with cases of CTVT in Brazil, in English or Portuguese, published between 2000-2020. The CTVT was identified in 19 Brazilian states plus the Federal District, totaling 3,622 cases across the national territory, with the largest number of cases recorded in the Southeast region. The cytological exam was the most used for the diagnosis of CTVT (89.2 %), followed by histopathological (37.8 %) and immunohistochemistry (13.5 %)¹ . Predominant epidemiological aspects of CTVT identified in the study were: Mixed breed dogs (75.2 %), females (62.5 %), in adulthood (between 2 and 7 years) and dogs with free extra outdoor access (91.1 %). Genital presentation was the most frequent in the literature (86 %), followed by cutaneous (21.8 %), nasal (10 %), oral and lymph nodes presentations (10-5 %) and less frequent manifestations as ocular and anal/perianal (< 5 %). CTVT is a neoplasm widely distributed in Brazil, highly frequent and with several forms of clinical presentation, which can be underdiagnosed if there is no adequate knowledge of this tumor and its epidemiological characteristics. The extragenital manifestations of the neoplasm need further studies for its better characterization and more precise definition of its frequencies.

Immunocytochemical characterization of primary cell culture in canine transmissible venereal tumor

Abstract: Immunochemistry with anti-vimentin, anti-lysozyme, anti-alpha 1 antitrypsin, anti-CD3 and anti-CD79α antibodies has been used for characterization of primary cell culture in the transmissible venereal tumor (TVT). Samples for primary cell culture and immunohistochemistry assays were taken from eight dogs with cytological and clinical diagnosis of TVT. To validate the immunochemical results in the primary cell culture of TVT, a chromosome count was performed. For the statistical analysis, the Mann-Whitney test with p<0.05 was used. TVT tissues and culture cells showed intense anti-vimentin immunoreactivity, lightly to moderate immunoreactivity for anti-lysozyme, and mild for anti-alpha-antitrypsin. No marking was achieved for CD3 and CD79α. All culture cells showed chromosomes variable number of 56 to 68. This is the first report on the use of immunocytochemical characterization in cell culture of TVT. Significant statistic difference between immunochemistry in tissue and culture cell was not established, what suggests that the use of this technique may provide greater certainty for the confirmation of tumors in the primary culture. This fact is particularly important because in vitro culture of tumor tissues has been increasingly used to provide quick access to drug efficacy and presents relevant information to identify potential response to anticancer medicine; so it is possible to understand the behavior of the tumor.