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Amphibians, reptiles and fish
Unexpected but transient tumour enlargement preceded complete regression and long-term control after irradiation of squamous cell carcinoma in a red-eared slider (Trachemys scripta elegans)
  1. Alexie J Baja1,
  2. Gregory A Lewbart1,
  3. Jennifer A Luff2 and
  4. Michael W Nolan1
  1. 1Department of Clinical Sciences, North Carolina State University, Raleigh, North Carolina, USA
  2. 2Population Health and Pathobiology, North Carolina State University, Raleigh, North Carolina, USA
  1. Correspondence to Dr Michael W Nolan; mwnolan{at}


A red-eared slider with a chronic non-healing ulcerative shell lesion was diagnosed with cutaneous squamous cell carcinoma (SCC). The animal underwent surgical debulking and adjuvant hypofractionated radiation therapy. The lesion initially responded, with near-complete tumour regression, but then began growing again just a few months after finishing radiotherapy. Then, after several months with no additional tumour-directed therapy, the lesion again regressed. Five years post-irradiation and with no further treatment, the turtle now remains tumour-free. This unusual pattern of disease regression, followed by transient growth and then long-term local tumour control, suggests either a spontaneous remission or a pseudoprogression-like phenomenon. Careful clinical follow-up and reporting of future cases will aid in determining whether this pseudoprogression-like event was random, versus being a common component of the chelonian response to irradiation of cutaneous SCC.

  • tumours
  • reptiles
  • radiotherapy
  • pets
  • oncology
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  • Contributors AJB wrote the article. JAL reviewed the pathology and edited the article. MWN and GAL were the clinicians on the case, coordinated the efforts and edited the article.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article.

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