Skin diseases and palpable masses are a common presentation in guinea pigs brought for veterinary care2.
However, few studies have thus far looked at the prevalence of spontaneously arising diseases in pet guinea pigs.
"Lumpy bumpy guinea pigs: a retrospective study of 619 biopsy samples of externally palpable masses submitted from pet guinea pigs for histopathology" retrospectively analysed 619 biopsy samples submitted for histopathology from pet guinea pigs that had presented with externally palpable masses.
The purpose was to determine the most common tissue origins of these masses and the most frequent pathological diagnoses, together with signalment data for the most commonly diagnosed lesions.
Of the 619 samples submitted from 493 animals, 54 (8.7%) had arisen from the mammary glands3 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).
Forty-seven (7.6%) of the masses were diagnosed as inflammatory in nature, including dermatitis, panniculitis, lymphadenitis, cheilitis, myositis, sialoadenitis, abscess and chronic inflammation with osseous metaplasia.
Non-neoplastic, non-inflammatory lesions accounted for a further 31 (5.0%), namely cysts, hamartomas, hyperplastic lesions, polyps, ectopic bone formation and salivary gland steatosis.
The remainder of the samples were neoplastic in nature (541; 87.4%), with 99 masses classified as epithelial in origin, 347 as mesenchymal, 23 as round cell, five as melanocytic and eight as unclassified malignant neoplasms.
Of these, mesenchymal neoplasms were further subdivided into benign (288) and malignant (59).
Lipomas were the most common neoplasm diagnosed, accounting for 286 of all samples submitted.
Of all 619 samples included in the study, the eight most commonly diagnosed lesions were lipoma (46.2%), trichofolliculoma (12.3%), sarcoma (of various subtypes: 9.5%), inflammation (all sites 7.6%), lymphoma / leukaemia (3.4%), mammary carcinoma (4%), mammary adenoma (3.2%) and thyroid carcinoma (1.5%).
Overall these eight diagnoses accounted for 87.7% of all submissions from the externally palpable masses from the pet guinea pigs submitted for histopathology.
Melanie said: “Guinea pigs are an increasingly popular household pet.
"Skin diseases, including palpable masses, are a common reason for veterinary presentation. But few studies have been published to date that provide information for clinicians about these conditions.
“This study illustrates the importance of neoplasms of the skin and subcutis in pet guinea pigs, with over 87% of the cases analysed having one of eight diagnoses.
"While most of these neoplasms are benign, a substantial minority are malignant and identifying those lesions is especially important in treatment planning.
"Clinicians dealing with pet guinea pigs should also be aware that some externally palpable masses may arise from the thyroid or mammary glands rather than the skin or subcutis, and that male guinea pigs may also develop mammary lesions.”
The paper has been selected as ‘Editor’s Choice’ by the Journal of Comparative Pathology and will be free to access until September on Lumpy, bumpy guinea pigs: a retrospective study of 619 biopsy samples of externally palpable masses submitted from pet guinea pigs for histopathology - ScienceDirect.
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