Skip to content

Fibrosarcoma Was Reported in a Mute Swan for the First Time

Mute swan swimming on open water
Research · Disease, parasites & microbiology

Fibrosarcoma has been documented in a mute swan (Cygnus olor) for the first time. A UK case report published on 3 April 2026 describes a free-living adult male admitted to a wildlife hospital with two large skin masses over the keel.

The swan weighed 10 kg when admitted. One mass measured 8.9 × 2.1 cm and the other 4.2 × 3.2 cm, and the larger lesion was discharging purulent material. Initial treatment included anti-inflammatory medication and antimicrobials, but the masses continued to grow and the bird lost 1.4 kg over 21 days. Blood tests showed marked heterophilia—an increase in an important type of avian white blood cell—together with lymphopenia, a reduced proportion of lymphocytes. The authors considered stress as one possible contributor, but concluded that the pattern was more likely an immune response to bacteraemia in light of the systemic pathology found later.

Biopsy identified fibrosarcoma

Because the lesions were deteriorating despite treatment, the veterinary team took core biopsies under general anaesthesia. Histopathology — microscopic examination of the sampled tissue — showed an infiltrative soft-tissue tumour consistent with fibrosarcoma. Bacterial culture also identified Staphylococcus sciuri and Acinetobacter baumannii, with oxacillin resistance.

Post-mortem examination confirmed fibrosarcoma of the keel. The authors also identified inflammation and tissue damage in several internal organs and interpreted the systemic disease together with the bacterial infection as the most likely explanation for the bird’s continuing weight loss.

Treatment raised a wildlife-welfare problem

The tumour had a broad base and was locally infiltrative. According to the authors, removing it with adequate margins would have left a large wound that would need prolonged healing and repeated bandaging. This would also have prevented normal access to water for an extended period, restricting swimming and preening and complicating a successful return to the wild.

The veterinary team therefore chose euthanasia. The authors use the case to emphasise that treatment decisions for free-living animals must consider both the medical prognosis and whether prolonged rehabilitation would prevent essential natural behaviour.

Fibrosarcoma is known from other bird groups but had not previously been reported in a swan. The authors recommend that veterinarians include neoplasia among the possible causes of persistent skin masses in free-living swans and note that biopsy can provide a rapid diagnosis when it can be performed safely.

Sources and image credit

  1. McKinney, R. A., & Hughes, K. (2026). Integumentary fibrosarcoma in a free-living swan (Cygnus olor): Medical and welfare considerations. Veterinary Record Case Reports, 14(2), e70429.Primary peer-reviewed open-access case report, first published 3 April 2026. The authors report the first documented fibrosarcoma in a swan.

Image: Charles J. Sharp — mute swan at Wolvercote, Oxford, photographed 12 March 2014; representative species image. Source: Wikimedia Commons. · CC BY-SA 3.0 · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

Disease, parasites & microbiology

SPECIES IN THIS STORY

Species in this story

Mute Swan Cygnus olor Explore species

Independent research and conservation news archive

Did you find this information useful?

Wildlife Vagabond is independently built and maintained. Voluntary support helps cover source verification, hosting and continued work on research and conservation news.

Support Wildlife Vagabond

The news archive will remain freely available.