Bleomycin-based electrochemotherapy for recurrent oral CD8-positive epitheliotropic T-cell lymphoma in a dog with...

Oral epitheliotropic T-cell lymphoma (ETCL) is an uncommon form of canine cutaneous lymphoma involving the oral mucosa and mucocutaneous junctions. Information regarding optimal treatment strategies and prognosis is limited. Electrochemotherapy (ECT) has demonstrated efficacy against various cutaneous and subcutaneous tumors in dogs and cats; however, reports describing its use for canine oral ETCL are scarce.

A 13-year-old male Beagle presented with multiple nodular lesions involving the right maxillary gingiva, buccal mucosa, and mandibular gingiva. Histopathology and immunohistochemistry confirmed CD8-positive epitheliotropic T-cell lymphoma, with more than 90% of neoplastic cells expressing CD3 and CD8. Initial treatment with oclacitinib resulted in a reduction in the size and number of the oral lesions; however, disease progression was observed after 149 days. Bleomycin-based electrochemotherapy (BLM-ECT) was subsequently performed using intravenous bleomycin (20 mg/m²) followed by electric pulse delivery with a four-needle electrode (1,000 V/cm, eight pulses). Two BLM-ECT sessions were administered on days 205 and 238, resulting in marked reduction in the size and number of the oral lesions and prolonged local disease control. On day 354, enlargement of the left mandibular lymph node was observed. Histopathological examination revealed extensive necrosis that precluded definitive determination of lymphoma involvement. Although residual CD3-positive lymphocytes were identified, neither flow cytometry nor polymerase chain reaction for antigen receptor rearrangement (PARR) confirmed a neoplastic lymphoid population. A third BLM-ECT session was performed on day 555 for recurrent erythematous lesions of the median upper and lower lip mucosa, in which T-cell lymphoma was histologically confirmed. At the latest evaluation on day 608, no grossly visible oral lesions were detected, and there was no clinical evidence of systemic dissemination. The dog remained clinically well.

BLM-ECT provided prolonged local disease control in a dog with recurrent multifocal oral CD8-positive ETCL that had progressed despite oclacitinib treatment. Unusual necrotic changes also developed in regional lymph nodes. The etiology of these changes remained undetermined, and a causal relationship with ECT could not be established. Investigation of pathological and immunological changes following ECT is warranted. BLM-ECT may represent a feasible and repeatable local treatment option for selected dogs with oral ETCL.