Recurrence rate of corneal squamous cell carcinoma in dogs undergoing superficial keratectomy surgery

Abstract

Background: Corneal squamous cell carcinoma (cSCC) is a rare neoplasm of dogs that can be treated with various modalities, principally by superficial keratectomy (SK) surgery. It is common to treat cSCC with multiple adjunctive therapies, but this may not always be practical for clinicians, clients, or patients.

Aim: This retrospective study describes the signalment of affected dogs, concurrent medical therapy, and success rate of surgical treatment of cSCC with SK surgery alone or in combination with adjunct therapy.

Methods: Eligible dogs undergoing SK surgery for histologically confirmed cSCC were selected from medical records (2009-2024) of Animal Eye Care, Melbourne. Records were examined for cSCC recurrence at follow up.

Results: Between January 2009 and August 2024, 16 eyes from 14 dogs (5 male; 35.7% (37.5% eyes), 9 female; 64.3% (62.5% eyes) had a confirmed histopathological diagnosis of cSCC following SK surgery. All cases were diagnosed within the last 9 years. There was a notable predilection of brachycephalic breeds (85.7% of dogs; 81.3% of eyes) with pugs the most overrepresented (42.9% of dogs; 37.5% of eyes). The average age at diagnosis was 8.7 years (range 2.1-13.8). Tumor recurrence occurred in two cases following incomplete excision, with no tumor recurrence reported following a second SK surgery. Adjunctive therapy was used in four cases and included cryotherapy and topical interferon alpha-2a. At the time of diagnosis, 12 out of 16 eyes had been treated previously with topical immunomodulatory therapy. Prevalence data varied but peaked in 2021 with 0.14% of total patients and 0.82% of all brachycephalic patients diagnosed with cSCC.

Conclusion: Complete excision of cSCC by SK surgery is effective for preventing the recurrence of cSCC in dogs, even in the absence of adjunctive therapies. Dogs with chronic corneal inflammatory conditions, particularly brachycephalic breeds, are at higher risk for developing cSCC. Corneal SCC should be suspected in middle-aged brachycephalic dogs presenting with proliferative, raised, or hyperaemic corneal lesions.

Keywords: Canine; Eye; Immunomodulatory; Tacrolimus; Tumor.

Fig. 1.. Clinical progression of case 8. (A) raised opacities with associated vascularisation were seen 7 months prior to initial SK surgery. (B) 8 days following initial SK surgery, the surgical site was epithelialized with prominent corneal vascularisation present. (C) 1 month following initial SK surgery the cornea was clear and only very faint vascularisation remained. (D) 1 year 7 months following initial SK, recurrence of the incompletely excised cSCC was demonstrated. Repeat SK was performed 1 month later.

Fig. 2.. Clinical progression of case 9. (A) vascularisation and scarring of the dorsomedial cornea were seen 1 year prior to SK surgery. (B) increased opacification and dense, raised vascularisation with an irregular cobblestone appearance was noted a year later, 2 weeks prior to SK surgery. (C) improved corneal clarity and a more discrete, localised, irregular, raised, pink growth was seen 7 days later, 7 days prior to SK surgery, following treatment with topical dexamethasone, topical Polymixin B sulfate/Bacitracin zinc/Neomycin sulfate triple antibiotic ointment, systemic doxycycline and systemic carprofen.