Study gives new insights on neoplasia in guinea pigs

15 January 2025

Although neoplasia is considered one of the most common diseases in geriatric guinea pigs, there has been little research on tumour prevalence of all organ systems, and on patient demographic information.

A new study by Christof Bertram and others published in the Journal of Veterinary Diagnostic Investigation assessed the frequency of different tumour types in guinea pigs grouped by organ system, the potential of metastasis, and the predisposition of age and sex to developing tumours1.

Using autopsy reports retrospectively collated from three pathology institutes in Germany, Austria and USA, data were extracted on age at death, sex, presence of neoplasia, organ affected by neoplasia, and tumour type. Of a total of 2,474 guinea pigs autopsied, tumours were found in 21% (508 cases), with multiple tumours found in 95 cases (2 tumours in 79 cases; 3 tumours in 11 cases; 4 tumours in 3 cases; 5 and 6 tumours in 1 case each).

Lymphomas or leukaemias were the most common tumour type of any organ system, particularly in younger animals (mean age being 51 months, compared with 60 months for non-lymphoid tumours). Lymph nodes, liver and spleen were the most frequently affected organs. Non-lymphoid tumours were most commonly found in the female genital tract, mostly uterus; lungs; skin including the mammary gland; endocrine system, mostly thyroid gland; and alimentary system, mostly the gastrointestinal tract.

Particularly low tumour prevalence was found in the nervous system, male genital tract and sensory organs (such as eyes). Non-lymphoid tumours were classified as malignant in half of cases and metastasis of malignant non-lymphoid tumours was reported in 19% of tumours, meaning only 1.7% of the entire study cohort had metastatic non-lymphoid tumours.

Tumour prevalence increased from 1% in guinea pigs less than 0.5 years old to 54% for animals over 5 years old, with a mean age of death of 56 months, and was higher in intact females.

It has previously been considered that tumour prevalence in guinea pigs was low, based on research on laboratory animals which are typically younger. However, this new study found a tumour in one in five guinea pigs, higher than that for pet rabbits studied at the same institution.

The main study limitations were that tumour diagnoses were retrieved from the original autopsy reports, as re-evaluation of tumours wasn’t possible; the diagnostic criteria for classification of tumour types were likely inconsistent between different pathologists and over time; and demographic information wasn’t available for some patients, resulting in breed being excluded as a risk factor.

Future studies are needed of potentially aggressive tumours to determine prognostic markers and effectiveness of different treatments, and more detailed evaluation of the histologic and immunohistochemical tumour characteristics to give further information on the clinical impact of these neoplasms.

Take home message

Tumour prevalence in guinea pigs is higher than previously thought, with tumours found in 21% of guinea pigs, and increases with age. Lymphomas or leukaemias were the most common tumour type, most frequently affecting lymph nodes, liver and spleen, while non-lymphoid tumours were mostly found in the female genital tract, lungs, skin, endocrine system, and gastrointestinal tract.

Reference

1Bertram CA, Donovan TA, Bertram B, Sabara J & Klopfleisch R (2024) Neoplasia in pet guinea pigs: a retrospective analysis of 2,474 autopsy examinations. Journal of Veterinary Diagnostic Investigation. doi:10.1177/10406387241288642