Mammary and reproductive tract tumours and tumour-like lesions of 286 small pet mammals: a retrospective study.

Small mammals are very popular companion animals, and the incidence of particular tumour types in these animals is the subject of extensive research. We carried out a retrospective and comparative analysis of the incidence of reproductive tract and mammary tumours and tumour-like lesions collected from 103 pet rabbits, 75 pet rats, 71 guinea pigs, 12 mice, 11 hamsters, eight African pygmy hedgehogs, four ferrets and two chinchillas. The results indicate that uterine tumours and tumour-like lesions are common in pet rabbits, guinea pigs and African pygmy hedgehogs. In pet rabbits, the most common uterine tumour was endometrial adenocarcinoma, while in guinea pigs benign lesions predominated (ie, leiomyoma, endometrial adenoma, cystic endometrial hyperplasia and deciduoma). Uterine tumours in African pygmy hedgehogs included adenosarcomas and endometrial polyps. Ovarian lesions were found only in guinea pigs (ovarian rete adenomas, rete cysts) and African pygmy hedgehogs (mostly granulosa cell tumours), while testicular tumours were diagnosed in pet rabbits, one pet rat and one guinea pig. Mammary tumours were common in pet rabbits, pet rats, guinea pigs, mice, hamsters and African pygmy hedgehogs. In pet rats, the most common mammary tumour was fibroadenoma, while in other animals carcinomas predominated. In guinea pigs and, to a lesser extent, in pet rats, a significant percentage of mammary tumours occurred in males. Guinea pigs seem to be predisposed to mammary tumours of ductal origin. This study describes for the first time uterine angioleiomyoma in the pet rabbit and mammary spindle cell carcinoma in the Djungarian hamster and chinchilla.

Expression of programmed cell death protein 1 and programmed cell death ligand 1 in feline injection site fibrosarcomas.

Feline injection site fibrosarcomas represent a unique challenge in veterinary oncology due to their association with injection sites and aggressive behaviour. The study explores the expression of immune checkpoints programmed cell death protein 1 and programmed cell death ligand 1 in the malignancy, aiming to unravel their potential significance in tumour progression. The study included 31, archival diagnostic specimens of feline fibrosarcomas, located in the common injection sites. The programmed cell death protein 1 and programmed cell death ligand 1 expression in tumour cells and tumour infiltrating lymphocytes were assessed by immunohistochemical methods. Programmed cell death protein 1 and programmed cell death ligand 1 expression were observed in 84% and 81% of cases, respectively. In tumour infiltrating lymphocytes the PD-1 expression was observed in 71% of cases. Notably, higher programmed cell death protein 1 expression correlated with tumour grade and heightened inflammation score, suggesting a potential association with tumour aggressiveness. Similarly, programmed cell death ligand 1 expression exhibited a positive correlation with tumour grade and inflammation score. The observed findings suggest a potential role for programmed cell death protein 1 and programmed cell death ligand 1 in tumour progression and immune response within the tumour microenvironment. Moreover, this study contributes to a deeper understanding of feline injection site fibrosarcoma pathogenesis, emphasizing the importance of considering immunological perspectives in developing effective treatment strategies for this challenging condition. Further investigations are warranted to advance our knowledge and refine therapeutic approaches for feline injection site fibrosarcoma management.

Metallothionein expression in feline injection site fibrosarcomas.

BACKGROUND: Feline injection site fibrosarcoma is an aggressive and infiltrative tumour arising in the background of chronic inflammation. The aim of this study was to evaluate the expression of metallothionein (I-II) in feline injection site fibrosarcomas and to assess its possible relationships with Ki67 index, inflammation score and tumour grade. The study included 40 feline fibrosarcomas, located in the common injection sites (i.e., interscapular area, thigh, flank), constituting archival diagnostic specimens collected between 2019-2020. Tumours were graded histologically according to the newly proposed soft-tissue sarcoma grading system in cats. Immunohistochemistry was performed to evaluate the expression of Ki67 and metallothionein in tumour cells. RESULTS: The cytoplasmic and sometimes nuclear expression of metallothionein was observed in all tumours grade I, 66.67% of tumours grade II and 55% of tumours grade III. The expression of metallothionein was negatively correlated with tumour grade and inflammation score, while the Ki67 index was positively correlated with tumour grade, inflammation score and necrosis score. CONCLUSION: The downregulation of MT expression in feline injection site fibrosarcomas seems to be connected with an increase in the inflammatory infiltration, hence tumour progression. This is the first study describing metallothionein expression in feline injection site fibrosarcomas.

Cutaneous and Subcutaneous Tumours of Small Pet Mammals-Retrospective Study of 256 Cases (2014-2021).

Since small mammals are gaining popularity as pets in Poland, the number of tumour samples submitted for histopathological examination is quite high. This study was a retrospective analysis of cutaneous and subcutaneous tumours in small pet mammals submitted for histopathology in 2014-2021. The analysis included 256 tumours sampled from 103 guinea pigs, 53 rats, 43 pet rabbits, 21 ferrets, 17 hamsters, 8 degus, 5 African pygmy hedgehogs, 3 Mongolian gerbils and 3 chinchillas. Tumours were diagnosed based on routine histopathology, with additional immunohistochemistry when necessary. The results of this study revealed that the vast majority of cutaneous tumours in guinea pigs were benign, with a predominance of lipoma. Adnexal tumours constituted a significant percentage of cutaneous tumours in guinea pigs (24.3%, with the most common being trichofolliculoma), pet rabbits (46.5%, with the most common being trichoblastoma), ferrets (33.3%, mostly derived from sebaceous glands), hamsters (52.9%, with the most common being trichoepithelioma) and gerbils (66.7%, scent gland epithelioma). Soft tissue sarcomas were a predominant group of tumours in rats (52.8%, with the most common being fibrosarcoma), African pygmy hedgehogs (100%), degus (87.5%) and chinchillas (66.7%). Melanocytic tumours were only sporadically seen in small mammal pets. Mast cell tumours were diagnosed only in ferrets, while epitheliotropic T-cell lymphoma was diagnosed only in a hamster and a degu. In summary, malignant tumours constitute a significant percentage of cutaneous tumours in many species of small mammal pets. Therefore, each cutaneous tumour should be sampled for further cytologic or histopathologic diagnosis.

Mutations of p53 Gene in Canine Sweat Gland Carcinomas Probably Associated with UV Radiation.

INTRODUCTION: Apocrine sweat gland carcinomas (ASGCs) are rare malignant skin tumours in dogs and humans. The literature published so far focuses mostly on the clinico-epidemiological aspect of these tumours, but little is known about their pathogenesis. In this study we aimed to determine whether the p53 gene is involved in the carcinogenesis of the apocrine sweat gland in dogs and whether ultraviolet radiation (UV) is related to it. MATERIAL AND METHODS: Forty canine ASGCs were submitted to laser capture microdissection to isolate neoplastic cells, from which DNA was subsequently extracted. PCR amplification and sequencing of p53 exons 2-8 was then performed, followed by computer analysis of the obtained sequences. RESULTS: Sixteen mutations within the p53 gene were found in 13 tumours. The mutations involved C → T, T → C, G → A, and CC → TT transitions, C → G transversion and adenine deletion, which are gene alteration types known to be related to UV radiation in the process of skin carcinogenesis in humans. Six of the thirteen tumour cases displayed the C → T transitions in the same location in exon 4 and three of the thirteen cases displayed T → C in the same location in exon 5. CONCLUSION: The results of the present study indicate both the participation of the p53 gene and the influence of UV radiation in the formation of ASGCs in dogs.

Diagnostic immunohistochemistry for canine cutaneous round cell tumours - retrospective analysis of 60 cases.

INTRODUCTION: Canine cutaneous round cell tumours (CCRCTs) include various benign and malignant neoplastic processes. Due to their similar morphology, the diagnosis of CCRCTs based on histopathological examination alone can be challenging, often necessitating ancillary immunohistochemical (IHC) analysis. This study presents a retrospective analysis of CCRCTs. MATERIALS AND METHODS: This study includes 60 cases of CCRCTs, including 55 solitary and 5 multiple tumours, evaluated immunohistochemically using a basic antibody panel (MHCII, CD18, Iba1, CD3, CD79a, CD20 and mast cell tryptase) and, when appropriate, extended antibody panel (vimentin, desmin, a-SMA, S-100, melan-A and pan-keratin). Additionally, histochemical stainings (May-Grünwald-Giemsa and methyl green pyronine) were performed. RESULTS: IHC analysis using a basic antibody panel revealed 27 cases of histiocytoma, one case of histiocytic sarcoma, 18 cases of cutaneous lymphoma of either T-cell (CD3+) or B-cell (CD79a+) origin, 5 cases of plas-macytoma, and 4 cases of mast cell tumours. The extended antibody panel revealed 2 cases of alveolar rhabdo-myosarcoma, 2 cases of amelanotic melanoma, and one case of glomus tumour. CONCLUSIONS: Both canine cutaneous histiocytoma and cutaneous lymphoma should be considered at the beginning of differential diagnosis for CCRCTs. While most poorly differentiated CCRCTs can be diagnosed immunohis-tochemically using 1-4 basic antibodies, some require a broad antibody panel, including mesenchymal, epithelial, myogenic, and melanocytic markers. The expression of Iba1 is specific for canine cutaneous histiocytic tumours, and more sensitive than CD18. The utility of CD20 in the diagnosis of CCRCTs is limited.

Dirofilaria repens-An etiological factor or an incidental finding in cytologic and histopathologic biopsies from dogs.

Dirofilaria repens is an endemic, zoonotic parasite of carnivores, causing subcutaneous dirofilariasis, which is mostly asymptomatic. The aim of this study was to describe 22 cases of canine subcutaneous dirofilariasis. The cytologic and histopathologic samples were collected from dogs, which presented with various clinical signs such as cutaneous/subcutaneous nodules, hydropericardium, ascites, and lymphadenomegaly. The cytologic or histopathologic examination revealed purulent, pyogranulomatous, granulomatous or eosinophilic dermatitis/panniculitis, and the presence of D repens microfilariae or adults. The microfilariae or adults were also found incidentally in neoplastic cutaneous or subcutaneous tumors and in a sialocele. For the first time, microfilariae were also detected and described in pericardial and abdominal effusions and in enlarged reactive lymph nodes. Although it is well known that D repens can cause dermatitis and panniculitis in dogs, no previous reports of D repens microfilariae in body cavity fluids were found. The role of this parasite in the accumulation of body cavity fluid or in reactive lymphadenomegaly requires further investigation. Due to its zoonotic potential, and apparently underestimated pathogenicity, each case of canine subcutaneous dirofilariasis should be treated.