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

Neoplasia in pet guinea pigs: a retrospective analysis of 2,474 autopsy examinations

Neoplasia is a common disease in guinea pigs (Cavia porcellus); however, few studies have evaluated the prevalence of neoplasia in all organ systems. We retrospectively analyzed the tumor prevalence in pet guinea pigs and the frequency of metastasis in a multi-institutional study population of 2,474 autopsy cases. Tumors were found in 508 guinea pigs (prevalence: 20.5%), of which 95 cases had >1 tumor, resulting in a total of 627 tumors. The tumor prevalence increased from 1.4% in animals <0.5-y-old to 53.6% for guinea pigs >5-y-old. The most common tumor type was lymphoma or leukemia, affecting 174 guinea pigs (tumor prevalence: 7.0%). Lymphomas or leukemias were disseminated to various organs and/or lymph nodes in 146 (83.9%) cases and localized to 1 organ or 1 lymph node in 28 (16.1%) cases. Primary non-lymphoid tumors were most frequent in the female genital tract (62 of 1,235 cases, mostly uterus), respiratory system (116 of 2,474), skin including mammary gland (81 of 2,474), endocrine system (66 of 2,474, mostly thyroid gland), and alimentary tract (35 of 2,474). Tumors of the alimentary tract were dominated by gastrointestinal stromal tumors. Metastasis was detected in 42 of 453 non-lymphoid tumors (9.3%), with a surprisingly low frequency for pulmonary carcinoma and splenic hemangiosarcoma compared to other species. Our postmortem study demonstrates a high prevalence of disseminated lymphoma or leukemia in pet guinea pigs at the time of death or euthanasia. Additional studies are needed to further characterize these tumors.

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.

Disseminated histiocytic sarcoma in a degu (Octodon degus)

A 7-year-and-8-month-old, male degu (Octodon degus) with anorexia, depression, and labored breathing was found to have a thoracic effusion and enlargement of the right testis on radiographic examination. Despite treatment, the animal died. At necropsy, hepatomegaly, splenomegaly, and multifocal nodules on the intestinal serosa and mesentery were observed. Histologically, the foci were densely cellular invasive neoplasms composed of sheets of round to polygonal cells, with occasional multinucleated giant cells. Immunohistochemically, the neoplastic cells were immunopositive for ionized calcium-binding adapter molecule 1, human leukocyte antigen-DR, and CD204. These findings were consistent with disseminated histiocytic sarcoma.

What ails the pet rat? A retrospective study of more than 300 biopsy samples of externally palpable masses submitted from pet rats for histopathology (2013-2021)

Biopsy data on externally palpable masses in pet rats (Rattus norvegicus) were retrieved from the archives of a large commercial pathology laboratory between November 2013 and July 2021. A total of 330 samples were submitted from 292 individual animals. Of the 330 samples submitted, 182 (55.2%) were of mammary gland origin and the majority were benign neoplasms, with fibroadenoma most frequent. Of the remaining 148 samples, 101 were neoplastic in nature, with 76 tumours classified as mesenchymal, 23 as epithelial and two classified only as malignant neoplasia not otherwise specified. Malignant neoplasms accounted for 88 of these non-mammary masses, with the most diagnosed tumours including soft tissue sarcoma (including fibrosarcoma) and sarcomas not otherwise specified.

Pathological, histochemical, and immune-histochemical studies on some canine-skin neoplasm at Sharkia province, Egypt

Background

Cutaneous neoplastic disorders are often observed in small mammal pets, such as dogs, regardless of their gender.

Aim

An important objective of this work was to give a full account of the clinical, pathological, and immune-histochemical features of several skin tumors in dogs.

Methods

This study was a case series in the hospital clinic, Faculty of Veterinary Medicine, Zagazig University, Egypt. Twenty-five dogs (14 males and 11 females) were examined clinically during the period from March 2022 to October 2023. The skin swelling was collected from affected animals and then subjected to a detailed histopathological study to record the different gross and microscopic findings and confirm the diagnosis by immunohistochemistry.

Results

Skin neoplasia in dogs was exposed to various clinical signs, and the dogs' ages ranged between 3 and 11 years. Concerning tumor features, the majority of neoplasms were malignant (65.52%) more than benign (34.48%). The study revealed the presence of 29 cases of dogs showed neoplasia with different prevalence rates including squamous cell carcinoma (13.79%), mast cell tumor (6.89%), basal cell tumors (10.34%), histiocytoma (6.89%), trichoepithelioma (10.34%), transmissible venereal tumor (10.34%), trichilemmoma (3.44%), scalp paraganglioma (3.44%), pilomatricoma (10.34%), malignant melanomas (17.24%), and miscellaneous cases as fat necrosis (6.89%), in males and females dogs with different histopathological lesions and immunohistochemistry expressions for pan-cytokeratin (CK), melanocyte-differentiation antigens (S100 protein), and synaptophysin.

Conclusion

Malignant melanomas (17.24%) are the extremely common cutaneous tumors diagnosed in this study. Meanwhile, benign tumors such as trichilemmoma, trichoepithelioma, pilomatricoma, and paraganglioma are less frequent in dogs.

Respiratory Distress Caused by Neoplastic Upper Respiratory Tract Obstructions in 2 Pet Rats (Rattus norvegicus domestica)

Respiratory disease is one of the primary reasons for pet owners to seek veterinary attention for their rats. While chronic respiratory disease complex is most often responsible for respiratory signs in pet rats and is well characterized, upper respiratory obstructive disease has been rarely reported in the literature. This report describes 2 pet fancy rats (Rattus norvegicus domestica) presenting with a several day history of progressive respiratory signs that were minimally responsive to supportive therapies, including antibiotics, nonsteroidal anti-inflammatories, and fluid and oxygen support. Survey radiographs were performed under sedation in both cases. In the first case, no cause for the clinical signs could be identified, in part due to suboptimal radiographic positioning, although severe aerophagia was noted. In the second case, cervical tracheal luminal narrowing and increased soft tissue opacity along the walls of the trachea were identified. Both rats declined while under sedation, resulting in cardiopulmonary arrest in the first case and humane euthanasia in the second. On necropsy, the first case had a oropharyngeal squamous cell carcinoma originating from the Zymbal's gland, which was obstructing the larynx. The second case had an intra-luminal tracheal mass obstructing the airway. This was mostly likely B-cell lymphoma or a plasma cell tumor, although definitive diagnosis was unable to be obtained. For future such cases empiric management of respiratory disease in rats with antimicrobials, anti-inflammatories, and supportive care is often appropriate based on the high prevalence of infectious agents, however, other noninfectious causes should be considered, such as neoplastic processes leading to upper airway obstructive disease and diagnostic imaging may be indicated.

Analysis of occurrence and risk factors associated with pet rabbits' tumors in Central Thailand

Rabbit oncology is gaining more attention as more pet rabbits are surviving beyond their normal lifespans. Due to the limited epidemiological information on pet rabbits' tumors in Thailand, this study aimed to report the prevalence and the potential risk factors associated with tumors in pet rabbits in Thailand. From 2018 to 2022, 93 tissue biopsies from tumor-suspected lesions on pet rabbits were gathered from animal hospitals in Bangkok and Chonburi provinces, Thailand. According to histopathology confirmation, tumors and tumor-like lesions were diagnosed. In this study, the overall tumors were 67.74% (n=63) out of the submitted cases (n=93). The most commonly affected organ systems were reproduction (65.08%) and integumentary (22.22%). Rabbits older than 5 years were 3.85 times more likely to have reproductive tumors than younger rabbits (95% confidence interval (CI): 1.45-10.27, P≤0.01), and the most frequently occurring tumor type was uterine adenocarcinoma. Furthermore, male rabbits had a 17.02 times higher probability of developing cutaneous tumors than female rabbits (95% CI: 4.19-69.11, P≤0.001), and the most frequently occurring tumor type was soft tissue sarcoma. The results of this study thus suggested that the age and sex of the rabbits were potential risk factors for tumor development in Thailand. The knowledge gained from our study also provided the recommendation for owners to monitor their rabbits' health annually, particularly after late middle age, and rendered guidance for tumor detection in practical clinics.

Rabbit Dermatology

The majority of rabbit skin disease presentations can be divided into pruritus, alopecia, scaling, and nodules. Some disease will have more than one of these clinical signs. Ectoparasites, bacterial and fungal infections, and neoplasia account for most of the causes seen. Diagnostic tests include skin scraping and cytology, microbial culture, and biopsy. Therapy is dependent on cause. In addition to discussing the various causes and their treatments, important clinical care points are noted.

Lumpy, bumpy guinea pigs: a retrospective study of 619 biopsy samples of externally palpable masses submitted from pet guinea pigs for histopathology

Biopsy data on externally palpable masses in pet guinea pigs were retrieved from the archives of a large commercial pathology laboratory between November 2013 and July 2021. Of the 619 samples submitted from 493 animals, 54 (8.7%) had arisen from the mammary glands and 15 (2.4%) from the thyroid glands, with the remaining 550 (88.9%) involving the skin and subcutis, muscle (n = 1), salivary glands (n = 4), lips (n = 2), ears (n = 4) and peripheral lymph nodes (n = 23). Most of the samples were neoplastic, with 99 masses classified as epithelial in origin, 347 as mesenchymal, 23 as round cell, five as melanocytic and eight as unclassified malignant neoplasms. Lipomas were the most common neoplasm diagnosed, accounting for 286 of all samples submitted.