Abstract
Background:
Cutaneous mast cell tumor (MCT) is one of the most common skin neoplasms in cats and typically exhibits clinically benign behavior. Multiple MCTs, recurrent tumors, or infiltrated lymph nodes are associated with a more guarded prognosis. Surgery is the treatment of choice. However, the presence of multiple or large tumors can make the procedure challenging. Electrochemotherapy (ECT) is an effective local treatment, suitable for managing cutaneous or subcutaneous malignant tumors. This case series describes the first report of the use of ECT in the treatment of four cats with MCT.

Case Description:
Three cats presented with multiple MCTs, ranging from 7 to 50 nodules measuring 0.2 to 1 cm over the head and trunk, and one cat with a large tumor on the head measuring 4.6 cm. None of the patients had macroscopic metastasis detected on complete staging. Based on the anatomic region and limitations of systemic treatment, we proposed the use of ECT with intravenous bleomycin (15,000 IU/m²) as an alternative approach, and complete resolution of the tumors was observed in all patients after treatment. No tumor recurrence was detected during the follow-up period (range: 210–810 days). However, one patient developed new lesions at day 210. Local toxicity induced by ECT was graded as 1 (mild swelling) on a 6-point arbitrary scale (grades 0-5), and alopecia and scar tissue were observed after complete tumor remission. The number of ECT sessions ranged from one to two, with intervals of 14 to 45 days between sessions.

Conclusion:
The use of ECT may be successfully applied as a viable alternative approach for solitary or multiple mast cell tumors in feline patients as an alternative to surgery or in refractory cases, without significant toxicity, as observed in this case series report. Further research is warranted to support these preliminary findings.

Key words: Bleomycin, Electrochemotherapy, Electric pulses, Electroporation, Mast cell tumor