Rare Feline Gingival Extramedullary Plasmacytoma: Clinical Application of Electrochemotherapy for Local Control

Feline extramedullary plasmacytoma (EMP) is an uncommon plasma cell neoplasm typically regarded as biologically benign; however, its clinical behaviour may be heterogeneous. This case report describes an aggressive gingival EMP in a 14-year-old neutered male Turkish Angora cat, characterised by alveolar bone lysis and cytologically confirmed regional lymph node metastasis in the absence of systemic features consistent with multiple myeloma. Histopathological examination revealed an infiltrative round cell neoplasm with high mitotic index, and strong diffuse MUM-1 immunoreactivity confirmed the diagnosis. As complete surgical excision was declined, and tumour regrowth occurred after repeated radiation therapy, electrochemotherapy (ECT) was selected for local tumour control. Bleomycin (15,000 IU/m² IV) was administered before pulse delivery, and three ECT sessions were performed at weekly intervals. The tumour volume decreased by more than 70%, which was consistent with a partial response, and only mild self-limiting local adverse effects were observed. No systemic toxicity was observed. To the best of our knowledge, this is the first report describing the use of ECT for feline gingival EMP. This case highlights the potential biological heterogeneity of feline EMP and suggests that ECT may provide short-term local tumour reduction and palliation when complete surgical excision is not feasible.