Feline cutaneous and subcutaneous neoplasms

Tumours in European Shorthair cats: a retrospective study of 680 cases

OBJECTIVES

Naturally occurring tumours in domestic cats are less common than in dogs and represent the leading cause of death among older animals. The main objective of this study was to analyse a large data set of histologically diagnosed tumours to highlight the most common World Health Organization (WHO) tumour histotypes, the effect of age and sex, and the International Classification of Diseases for Oncology (ICD-O) topographical site predilections of feline breed-specific tumours.

METHODS

A total of 680 feline tumours diagnosed in European Shorthair cats by three veterinary diagnostic laboratories located in central Italy from 2013 to 2019 were collected. Data on age, sex and topography of lesions were recorded. Samples were morphologically and topographically coded using the WHO and the ICD-O-3 classification system.

RESULTS

Skin and soft tissue neoplasms comprised 55.9% of all tumours, followed by mammary gland (11%), alimentary tract (7.9%), oral cavity and tongue (7.3%), nasal cavity and middle ear (6%), lymph node (3.1%), bone (1.8%) and liver/intrahepatic bile duct (1.3%) tumours. Squamous cell carcinoma (SCC), sarcoma, lymphoma and basal cell tumours were the most diagnosed neoplasms. Malignant tumours were 82.9% of the total and the topographical sites mainly involved were skin (C44), connective/subcutaneous/other soft tissues (C49), mammary gland (C50), small intestine (C17), nasal cavity and middle ear (C30), and gum (C03).

CONCLUSIONS AND RELEVANCE

This study aimed to provide an in-depth evaluation of spontaneous feline tumours in the European Shorthair cat breed. Results identify SCC as the most commonly represented skin neoplasm. It is likely that the analysed feline population, living in southern latitudes, was more subject to prolonged exposure to ultraviolet light, explaining the discrepancy with previous studies in which SCC was less represented.

Canine and Feline Oral Cavity Tumours and Tumour-like Lesions: a Retrospective Study of 486 Cases (2015-2017)

Oral cavity tumours and tumour-like lesions are common in dogs and cats, and their diagnosis and classification requires histopathological examination. The aim of this study was to analyse retrospectively oral cavity lesions in dogs and cats in order to evaluate the distribution of inflammatory, hyperplastic and neoplastic lesions manifested as tumours. A total of 486 oral cavity tumours and tumour-like lesions (340 canine; 146 feline), diagnosed routinely from 2015 to 2017, were included. The lesions were classified as inflammatory, hyperplastic or neoplastic (benign and malignant). Histopathological diagnosis was based on haematoxylin and eosin staining and, when necessary, May-Grünwald-Giemsa (for mast cell tumours) or Masson's Fontana (for melanomas) stains or immunohistochemistry (for CD3, CD79α and S100 markers). For dogs, 29.11% (99/340) of the lesions were benign tumours, 24.12% (82/340) were hyperplastic lesions and 14.7% (50/340) were inflammatory lesions. For cats, 4.79% (7/146) were benign tumours, 15.07% (22/146) were hyperplastic lesions and 57.53% (84/146) were inflammatory lesions. Furthermore, 23.24% (79/340) of canine cases were diagnosed with gingival hyperplasia and 19.12% (65/340) were diagnosed with peripheral odontogenic fibroma, while 43.84% (64/146) of feline cases were diagnosed with chronic lymphoplasmacytic stomatitis. Malignant tumours in dogs and cats constituted 32.06% (109/340) and 21.91% (32/146) of the lesions, respectively, with high-grade melanoma in dogs and squamous cell carcinoma in cats being the most common.

Disseminated cutaneous mast cell tumors with epitheliotropism and systemic mastocytosis in a domestic cat

A 15-year-old female domestic, medium-haired cat presented to the referring veterinarian with a 2-month history of multiple, raised, disseminated, nodular skin lesions. A biopsy of 1 of the lesions was submitted to the Oklahoma Animal Disease Diagnostic Laboratory for evaluation. Histologically, there were multiple dermal nodules composed of sheets of neoplastic round cells. Multifocally, the neoplastic cells formed multiple small clusters of 3 to 5 cells within the epidermis. Distinct cytoplasmic granules were evident within the neoplastic cells with toluidine blue and Giemsa stains. The neoplastic cells were immunoreactive for c-KIT and lacked immunoreactivity for cluster of differentiation 3 with immunohistochemistry. Based on these findings, multiple epitheliotropic cutaneous mast cell tumors were diagnosed. The cat's health declined rapidly despite aggressive treatment, and the animal was humanely euthanatized. A complete necropsy revealed sheets of similar neoplastic mast cells within the spleen, liver, and individual cells scattered within the bone marrow. Exon 11 of the c-KIT messenger RNA from 1 of the cutaneous masses and the spleen was amplified with reverse transcription polymerase chain reaction, sequenced, and compared with the published c-KIT messenger RNA sequence from fetal cat tissues. The maximum identity was 100% for both tissue samples. To the authors' knowledge, the present report is the first to describe disseminated cutaneous mast cell tumors with epitheliotropism and systemic mastocytosis in a domestic cat.

Perforin expression in feline epitheliotropic cutaneous lymphoma

Cutaneous lymphomas are uncommon in people and companion animals. The tumors can be broadly categorized into epitheliotropic and nonepitheliotropic forms, which appear to have different biological behaviors. The present case describes a feline cutaneous epitheliotropic lymphoma. Masses in a 9-year-old cat were first identified on the tail. The cat was treated with chemotherapy, but additional skin masses developed on the flank, face, and ears. Local radiation induced transient tumor regression, but eventual dissemination prompted euthanasia 13 months after initial tumor appearance. Granular lymphocytes were consistently detected on blood smears, and histologically, the tumor involved the skin and superficial subcutis. Tumor lymphocytes expressed cluster of differentiation 3 (CD3) and perforin molecules, suggestive of a cytotoxic phenotype. Location, histopathological features, and perforin expression were similar to a distinct entity in human medicine designated primary cutaneous, CD8-positive, epidermotropic, cytotoxic, T-cell lymphoma.

Apparent clinical resolution of pinnal actinic keratoses and squamous cell carcinoma in a cat using topical imiquimod 5% cream

Imiquimod is a topical immune response modifier and stimulator used in humans to treat a number of cutaneous neoplasms. This case report describes a cat with actinic keratoses and squamous cell carcinoma of the pinnae. The pinnal lesions were treated with topical 5% imiquimod three times per week. Treatment was discontinued after 82 days of therapy. Twelve weeks of topical imiquimod application resulted in clinical resolution of the pinnal lesions. Although no post-treatment biopsies were performed, there was no relapse of the pinnal lesions in 5 months of clinical follow-up. Expected side effects were limited to erythema, crusting, alopecia, and mild discomfort at the sites of application during the first 3 weeks of application. These results suggest that topical imiquimod, although unproven, might be a therapeutic option or adjunct to therapy for cats with actinic keratoses and squamous cell carcinoma, especially those cats for whom surgery and radiation therapy are not an option.