EXPRESS: Carbon dioxide laser ablation as an alternative or adjunct treatment of Bowenoid in situ carcinoma (BISC) in five cats

Case series summary Five domestic cats diagnosed with Bowenoid in situ carcinoma (BISC) via histopathology were included in this retrospective case series. All cats presented with several dermatologic lesions including but not limited to hyperkeratotic plaques or crusts, focal alopecia, pigmented papules, erosions, and secondary pyoderma. The disease was gradually progressive in all cases, with a median time from lesion development to treatment of 365 days (range 84–1614 days). Four of five cats had no other clinical signs at time of presentation; one was pruritic. Each cat was treated with at least one session of carbon dioxide (CO2) laser ablation of the lesions under heavy sedation and local anesthetic or general anesthesia. No adverse events related to treatment were noted. Three cats had documented progressive disease (formation of recurrent or new lesions) at a median of 379 days (range 45–854 days) after first treatment (laser and/or surgery). Median time to progressive disease after first laser ablation was 158 days (range 35–379 days; n = 4 cats with follow-up available). Two cats were treated with CO2 laser more than once. One was in complete remission a total of 130 days after surgery and two laser ablation sessions. No cats developed metastatic disease. Relevance and novel information Feline BISC is a unique form of virally induced squamous cell carcinoma causing multifocal, superficial cutaneous lesions all over the body. This disease is often progressive, with cats developing regrowth of prior lesions or de novo ones, though deeper invasion and metastasis is rare. Historically, surgical excision and/or immunomodulation with imiquimod cream have been the mainstay of treatment. CO2 laser ablation is a new, well-tolerated, minimally invasive and effective alternative or adjunct treatment that can be repeated as new lesions arise.