Clinical, Cytological, Histological and Immunohistochemical Features of Cutaneous Mast Cell Tumours in Ferrets ( Mustela putorius furo )

Ferret Dermatology

Skin diseases commonly affect pet ferrets, with neoplastic, endocrine, and parasitic diseases being the most common. This review includes clinical presentation, diagnostic workup, and treatment of diseases with a dermatologic presentation in ferrets.

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

Simple Summary

Several species of small mammals are very popular as companion pet animals and therefore demand professional veterinary care, including proper diagnostic and treatment procedures. The incidence of neoplastic diseases in companion pet animals has increased over time, as it has in humans. The aim of this study was to evaluate the incidence of cutaneous tumours in small mammal pets, including guinea pigs, rats, pet rabbits, ferrets, hamsters, degus, African pygmy hedgehogs, Mongolian gerbils and chinchillas, submitted for histopathology in 2014–2021. Malignant tumours represented the predominant group of cutaneous tumours in rats, African pygmy hedgehogs, degus and chinchillas, and represented a significant percentage of lesions in guinea pigs, pet rabbits, ferrets, hamsters and Mongolian gerbils. We also described the first case of melanocytoma in a pet rabbit, epitheliotropic T-cell lymphoma in a degu, cutaneous histiocytic sarcoma in a Mongolian gerbil, fibrosarcoma in two chinchillas and epithelioid haemangioma in a chinchilla. The incidence of malignant neoplasms among spontaneous integumentary tumours submitted for histopathology is high in many species of small mammal pets. Therefore, each cutaneous tumour should be sampled for further diagnosis and treatment.

Abstract

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.

Pathology of Diseases of Geriatric Exotic Mammals

The review covers select disease conditions most frequently described in aging rodents (rats, mice, hamsters, guinea pigs), rabbits, and ferrets. The conditions are categorized by general organ systems, infectious diseases, and neoplasms. Two data systems, the Veterinary Medical Teaching Hospital and Comparative Pathology Laboratory at the University of California, Davis and Zoo/Exotic Pathology Service, Citrus Heights, California were used in the determining disease conditions to describe.

Neoplasia in Ferrets

Neoplasia is a common cause of disease in domestic ferrets worldwide. The most common neoplasms are islet cell tumors (insulinoma), adrenocortical neoplasms, and lymphoma. The definitive etiology has yet to be defined, but husbandry, genetic predisposition and infectious agents are postulated causes. Definitive diagnosis requires sampling and microscopic analysis of the neoplasm, but initial testing including blood, urine and diagnostic imaging can aid the diagnostic process. Based on the type of tumor and its location, therapeutic options include surgery, chemotherapy and radiation therapy. Numerous chemotherapeutic protocols and drugs have been published for the use in ferrets and a ferret specific formula for calculating body surface area has been established. In addition to the more commonly affected endocrine and hemolymphatic systems, ferrets can also develop tumors in the skin and subcutis, gastrointestinal and reproductive tracts, musculoskeletal, nervous, urinary, respiratory and vascular systems.

Comparative aspects of mast cell neoplasia in animals and the role of KIT in prognosis and treatment

Mast cell neoplasia clinical presentation and biological behaviour vary considerably across mammalian species, ranging from a solitary benign mass to an aggressive systemic malignancy. Mutations in the KIT Proto‐Oncogene Receptor Tyrosine Kinase (KIT) gene are common molecular abnormalities involved in mast cell tumorigenesis. KIT mutations often occur in dog, cat and human neoplastic mast cells and result in altered Kit protein structure and function. In dogs, certain KIT mutations are associated with more malignant and lethal disease. In contrast, KIT mutations in feline and human mast cell neoplasms are not correlated with prognosis, but are of value in diagnosis and treatment planning in humans. KIT genetic abnormalities have not been well investigated in other species, although aberrant cytoplasmic Kit protein staining detected in neoplasms of the ferret, horse and cow resembles aberrant Kit staining patterns detected in neoplastic mast cells of dogs, cats and humans. Mutations within KIT are classified as either regulatory‐type or enzymatic pocket‐type mutations according to their location within the KIT Proto‐Oncogene. Mutations within the enzymatic pocket domain confer tumour resistance to tyrosine kinase inhibitors (TKIs). Hence, knowledge of tumour KIT mutation status adds valuable information for optimizing patient treatment strategies. The use of TKIs in combination with conventional chemotherapeutics has opened a new treatment avenue for patients unresponsive to existing drugs. This review highlights the similarities and differences of mast cell neoplasia in mammals with a special focus on the involvement of KIT in the canine and feline forms in comparison to human mast cell neoplasia.

Electrochemotherapy with Bleomycin of Different types of Cutaneous Tumours in a Ferret (Mustela Putorius Furo)

Background

Mast cell tumour, sebaceous gland adenoma, and less common squamous papilloma are skin tumours in ferrets (Mustela putorius furo), and early excisional surgery is usually the treatment of choice. The aim of our study was to investigate the effectiveness of electrochemotherapy (ECT), a new, minimally invasive non-surgical method, as first treatment option of different types of ferret skin tumours located on surgically difficult sites.

Materials and methods

A 5-year-old castrated male ferret with two cutaneous masses, presenting 4 months apart and a 7-year-old spayed female ferret with two cutaneous masses, that appeared simultaneously on two locations are presented. In the first patient, both masses were diagnosed as mast cell tumours, and in the second patient, squamous papilloma and sebaceous adenoma were diagnosed. One session of ECT with bleomycin injected intratumourally was applied in all tumours.

Results

Complete response (CR) of all tumours was obtained, without recurrence during observation period of 15 months after ECT for first tumour and 11 months after ECT of the tumour located on the right hock in first patient, and 8 months after treatment for the second patient.

Conclusions

In present study, ECT with bleomycin proved to be safe and effective against different cutaneous tumours in ferrets. Due of good results, low cost and relatively easy procedure, ECT could be the treatment of choice instead of surgery for the selected skin tumours in ferrets.