Predominance of Granular Cell Tumours among Testicular Tumours of Rabbits (Oryctolagus cuniculi f. dom.)

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.

Neoplastic and non-neoplastic lesions in biopsy samples from pet rabbits in Hong Kong: a retrospective analysis, 2019-2022

Rabbits are popular pets in the urban environment of Hong Kong, ranking third behind cats and dogs. Here we describe the frequency of neoplastic and non-neoplastic lesions in biopsies from pet rabbits submitted to the CityU Veterinary Diagnostic Laboratory between 2019 and 2022, comprising 247 tissue samples from 243 rabbits collected by veterinarians in 19 veterinary clinics. Among the 243 rabbits, there were 128 females (65 spayed), 114 males (54 castrated); sex information was not provided for 1 rabbit. The rabbit breeds included 45 Lionhead, 35 Dwarf, 14 Lop, 11 Dwarf Lop, 5 French Lop, 3 Angora, 2 Dutch, 2 Holland Lop, and 1 each of Netherland Dwarf, Velveteen, Mini Lop, and New Zealand White. The mean ages of rabbits with neoplastic and non-neoplastic lesions were 7.1 and 5.7 y, respectively. The most common neoplastic lesions were adenocarcinoma (26.4%), trichoblastoma (21.4%), sarcoma (9.4%), and thymoma (8.2%). The most common non-neoplastic lesion was uterine cystic endometrial hyperplasia (14.8%), followed by dermal abscess formation in the ventral abdomen or skin of the head (12.5%). Although a broad spectrum of other lesions was described, our findings in biopsies from pet rabbits in Hong Kong are consistent with those in other jurisdictions.

Investigation of male genital system anatomy in the New Zealand rabbit ( Oryctolagus cuniculus L. )

Rabbits are frequently used in research because of their human-like biological structure. In the present study, 10 male rabbits were preferred. Arterial vascularization of the genital system organs were dissected. Morphometric and macroanatomical results of these organs were taken, and some organs were examined by magnetic resonance imaging (MRI). In this study, right testis length was measured at 67.24 ± 5.36 mm and left testis length was 62.25 ± 6.55 mm in New Zealand rabbits. Testicular weight was 10.21 ± 1.17 g on the right and 9.90 ± 1.15 g on the left. Right caput epididymidis 0.68 ± 0.08 g, left caput epididymidis 0.80 ± 0.13 g; right corpus epididymidis 0.14 ± 0.03 left corpus epididymidis 0.15 ± 0.03 g; right cauda epididymidis 1.87 ± 0.26 g left cauda epididymidis 1.90 ± 0.31 g. In the present study, right ductus deferens weight was 0.30 ± 0.29 g, and left ductus deferens weight was 0.25 ± 0.03 g; the ampulla ductus deferentis weight was 0.35 ± 0.16 g on the right side and 0.37 ± 0.16 g on the left side. The length of the vesicular gland glandula vesicularis was calculated as 18.54 ± 0.35 mm on the right and 17.55 ± 0.59 mm on the left. The width of the vesicular gland was measured as 16.54 ± 0.28 mm on the right and 16.70 ± 0.45 mm on the left. Vesicular gland weight was 0.91 ± 0.07 g on the right side and 0.96 ± 0.09 g on the left side. The prostate length was recorded as 11.68 ± 2.01 mm and width as 13.02 ± 1.38 mm. The length of the bulbourethral gland was 13.36 ± 2.00 mm on the right side and 12.39 ± 1.21 mm on the left. Its width was recorded as 6.73 ± 0.98 mm on the right and 5.80 ± 0.90 mm on the left. Respectively, it weighed 0.40 ± 0.20 g on the right and 0.44 ± 0.24 g on the left. The prostate consisted of three parts in rabbits: the proprostate, the corpus prostate and the paraprostate. The bulbourethral gland was a green lentil-sized gland found in pairs. It is thought that the obtained results will contribute to the scientific researches on male genital system in laboratory animals and other animal species, artificial insemination studies, reproductive system diseases and operations in rabbits.

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Rabbit

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and non-proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in most tissues and organs from the laboratory rabbit used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

Rhabdomyosarcoma on the Forelimb of a Common Musk Turtle (Sternotherus odoratus)

Malignant mesenchymal tumours are only rarely reported in turtles. In the present case, an 8-year-old female common musk turtle (Sternotherus odoratus) was presented with a solid, reddened, non-mobile mass on the right forelimb. The mass had a thin, membranous lining and a grey-white cut surface. Histological examination revealed a cell-rich, focally infiltrative neoplasm consisting of spindloid tumour cells arranged in bundles and streams. Rarely, indistinct cytoplasmic cross-striations were seen in the neoplastic cells. Transmission electron microscopy revealed cytoplasmic, disorganized muscle fibrils and haphazardly arranged, attenuated Z-lines in the neoplastic cells. The histological, histochemical and ultrastructural findings led to the diagnosis of a rhabdomyosarcoma. This is the first description of rhabdomyosarcoma in a freshwater turtle.

Neoplasia and Tumor-Like Lesions in Pet Rabbits (Oryctolagus cuniculus): A Retrospective Analysis of Cases Between 1995 and 2019

Prevalence and age distribution of tumors is largely unknown in pet rabbits. Currently available studies focused on specific organ systems or specific tumor types and never covered a comparative examination of all tumor types. Previous studies on laboratory rabbits suggested a low tumor prevalence but were mostly limited to young adult animals. In the present study, all tumor types and several tumor-like lesions of all organ systems were analyzed retrospectively in archived pet rabbit samples of all ages. Cases included necropsy cases ( n = 2,014) or postmortem tissue samples ( n = 102) as well as surgical biopsies ( n = 854). All lesions suspicious of neoplasia were reevaluated by histopathology and, when indicated, by immunohistochemistry. Necropsy cases had a tumor prevalence of 14.4% in both sexes or 19.8% in female intact rabbits of all age groups, and up to 47.2% or 66.7%, respectively, in rabbits older than 6 years. Overall, the most common tumor types were uterine adenocarcinoma (prevalence in female intact animals: 13.1%), lymphoma (prevalence: 2.8%), and thymoma (prevalence: 2.1%). Lymphoma, the most common tumor of rabbits ≤24 months of age, were of B-cell immunophenotype in 96% of cases and most commonly located in the lymph nodes (57%), gastrointestinal tract (54%), kidneys (48%), spleen (42%), and liver (41%). Tumors accounted for 81.1% of surgical biopsies and mostly comprised cutaneous, mammary, and uterine tumors. In conclusion, tumor types and prevalence varied significantly with respect to age, revealing some differences from previous studies on laboratory rabbits.