# Mapping Feline Oncology in Portugal: A National Characterization

## TL;DR

This study maps common cat cancers in Portugal, finding that most tumors are malignant and often occur in mammary glands and soft tissues, especially in older female cats.

## Contribution

The study provides the first national characterization of feline tumor patterns in Portugal, emphasizing malignancy prevalence and key anatomical sites.

## Key findings

- Malignant tumors accounted for 77.4% of cases, with mammary glands and soft tissues being the most common sites.
- Older female cats were more likely to have multiple tumors and malignant disease compared to younger or male cats.
- No significant geographical or breed-based patterns were found in tumor occurrence across Portugal.

## Abstract

Epidemiological studies play a key role in feline oncology by identifying which tumours are most common, in which patients they occur, and where they are most likely to arise. Mapping tumour occurrence in cats helps clinicians prioritise early diagnostic investigation, supports informed clinical decision-making, and contributes to earlier detection of malignant disease. This study evaluated feline tumour biopsies submitted across Portugal over five years. We analysed 1904 histopathology-confirmed neoplasms to describe where tumours arise, how often they are malignant, and the characteristics of most affected cats. Malignant tumours predominated (77.4%). Nearly nine in ten diagnoses involved two sites: the mammary gland (44.8%, predominantly in females) and the cutaneous/soft tissues (42.4%). Tumours of the gastrointestinal tract, oral cavity, eyes, urinary system and other organs were comparatively uncommon. Cats with malignant disease were older than those with benign lesions. Multiple tumours occurred in 8.3% of cats and were more frequent in older females. We found no meaningful patterns by breed nor evidence of geographical clustering within Portugal. For owners and clinicians, these results support prompt assessment of any new mass, particularly in older queens, and systematic palpation of mammary chains. Ongoing national surveillance of tumour patterns will help track changes over time and support better preventive care and outcomes.

This retrospective study describes the national histopathology caseload of feline tumours submitted to a Portuguese diagnostic laboratory over a five-year period. A total of 1904 histopathology-confirmed neoplasms were analysed by biological behaviour, anatomical location, and demographic/geographical variables. Malignant tumours predominated (77.4%), whereas 22.6% were benign. Tumours most commonly involved the mammary gland (44.8%) and cutaneous/soft tissues (42.4%), together accounting for 87.2% of cases; all other sites were individually uncommon (≤5.6%). The most frequent malignant tumour types were mammary carcinoma (38.3%), fibrosarcoma (8.0%), squamous cell carcinoma (6.4%), and mast cell tumour (4.8%). Cats with malignant tumours were older than those with benign lesions (p < 0.001), and females comprised most submissions (69.3%), largely driven by mammary neoplasia. Multiple, histologically distinct tumours were identified in 8.3% of cats and were more frequent in older females (p = 0.001). Domestic Shorthairs comprised the vast majority of cases, and no significant associations were detected between breed (including pure breeds) or geographical location and tumour occurrence or biological behaviour (p > 0.05). These findings highlight a sustained predominance of malignant disease in Portuguese cats, concentrated in mammary and cutaneous/soft-tissue sites, supporting a low threshold for biopsy in older cats and systematic mammary screening in females, and continued registry-based surveillance to monitor temporal changes in tumour patterns.