Vets in Lancashire said they were horrified when an abandoned dog was brought into a clinic suffering from infected open wounds and tumours.
The adult female Boxer-cross was dropped off at RSPCA Lancashire East branch in Accrington, on July 6, by two men who said they’d found her abandoned on the street.
The frightened Boxer had been riddled with tumours and was suffering from a ‘hideous’ open wound, said the vets.
Pictures taken by the RSPCA show the large, untreated tumours in her mouth and the excruciating open wound at the base of her tail that had become infected.
Some of the images are considered too graphic and upsetting to publish.
The vets said they had no option but to put her to sleep due to the severity of her injuries.
RSPCA officers are investigating how the neglected dog was abandoned and how the awful wounds were caused.
Investigating officer Demi Hodby said: “This poor girl had an absolutely hideous open wound on the base of her tail.
"Vets suspect it had been a tumour that had ulcerated before bursting and getting infected - it had obviously been this way - untreated - for some time.
"She also had a number of tumours in her mouth. She must have been in so much pain.
"Unfortunately, vets determined that there was nothing they could do to help her and made the heartbreaking decision to put her to sleep."
Staff believe the white dog was an older female, but her exact age is unknown.
Vets said she arrived wearing a leather and metal harness, but had no identification and had not been microchipped.
RSPCA officers are investigating how she suffered such a nasty wound and why it had been left untreated for so long.
Demi added: "I’m appealing to the public to contact us if they recognise this dog or if they know someone who owned a similar dog in the local area.
"I’d also like to hear from anyone who saw a dog matching her description with a wound like this - it was so huge and horrible that it would be impossible to miss.
"Anyone who may be able to assist with our enquiries should call our appeal line on 0300 123 8018."
To help the RSPCA continue rescuing, rehabilitating and rehoming animals in desperate need of care please visit www.rspca.org.uk/give.