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Published on: October 28, 2021
Extraskeletal osteosarcoma in two Guinea pigs (Cavia porcellus).
Crisan Smaniotto1, Vinicius Dahm1, Amália Ferronato1
1Universidade Federal do Paraná - Setor Palotina, Rua Pioneiro, 2153, Jardim Dallas, CEP 85953-128, Palotina, Paraná, Brazil.
Journal of Comparative Pathology
|June 22, 2026
Summary
Extraskeletal osteosarcoma (EOS) is rare in guinea pigs. This study details two cases, highlighting the importance of integrated diagnostic methods for accurate identification and understanding of this rare cancer in exotic pets.
Area of Science:
- Veterinary Pathology
- Oncology
- Exotic Animal Medicine
Background:
- Extraskeletal osteosarcoma (EOS) is a rare malignant tumor originating from mesenchymal cells, typically affecting soft tissues rather than bone.
- While documented in domestic animals like dogs and cats, EOS is infrequently reported in non-domestic species.
- Accurate diagnosis of EOS is crucial for appropriate treatment and prognosis in affected animals.
Purpose of the Study:
- To report and characterize two distinct cases of extraskeletal osteosarcoma (EOS) in guinea pigs (Cavia porcellus).
- To correlate clinical, radiographic, pathological, and immunohistochemical findings in these guinea pig EOS cases.
- To contribute to the understanding of the clinicopathological spectrum of EOS in guinea pigs.
Main Methods:
- Case presentation of two guinea pigs diagnosed with EOS.
- Radiographic evaluation to assess tumor location, extent, and skeletal involvement.
- Histopathological examination to confirm neoplastic mesenchymal proliferation with osteoid production.
- Immunohistochemical analysis using markers such as vimentin, RUNX2, S100, alpha-smooth muscle actin, Ki-67, and p63.
Main Results:
- Case 1 presented with mesenteric and pancreatic nodules; Case 2 had a subcutaneous mass with distant metastases.
- Radiographs showed soft tissue masses with mineralization but no bone involvement in both cases.
- Histopathology confirmed malignant mesenchymal tumors with osteoid deposition.
- Immunohistochemistry revealed strong positivity for vimentin and RUNX2 in neoplastic cells, with variable results for other markers.
Conclusions:
- These cases expand the known clinicopathological presentations of extraskeletal osteosarcoma in guinea pigs.
- A comprehensive diagnostic approach combining radiography, histopathology, and immunohistochemistry is essential for accurate EOS diagnosis in guinea pigs.
- Further research may elucidate specific immunohistochemical markers for definitive EOS diagnosis in non-domestic species.
