Surgical resection and angularis oris axial pattern flap reconstruction with adjuvant radiation therapy for recurrent soft palate leiomyosarcoma in a dog

Abstract

Leiomyosarcoma of the oral cavity is extremely rare in both human and veterinary medicine. To the best of our knowledge, this is the first report describing the clinical course and multimodal treatment of a canine leiomyosarcoma arising in the soft palate. A 3-year-old, spayed female Pungsan dog was presented with a recurrent soft palate mass, dyspnea, epistaxis, and anorexia. The patient had a history of two prior surgeries involving incomplete excisions, both resulting in a diagnosis of oral sarcoma. The tumor exhibited aggressive recurrence, with rapid growth intervals of 3 months and 3 weeks, respectively. Computed tomography revealed a large soft tissue mass (3.8 × 3.5 × 4.4 cm) occupying most of the pharyngeal space. Marginal excision with reconstruction using an angularis oris axial pattern flap was performed, followed by adjuvant radiation therapy. Histopathology and positive immunohistochemistry for desmin and smooth muscle actin confirmed the diagnosis of leiomyosarcoma. Although the patient remained stable, a 2.5-mm recurrent nodule was detected 9.5 months post-irradiation. As the tumor progressed and further surgical intervention was declined, a second course of radiation therapy was administered at the 14-month mark. Three months later, the patient experienced episodic dysphagia but subsequently recovered her general condition. The patient was lost to follow-up 21.5 months post-surgery. During the clinical course, fistula formation occurred in the early post-irradiation period, followed by progressive thinning of the soft palate, including the reconstructed flap, over long-term follow-up. The soft palate leiomyosarcoma in this patient was characterized by highly aggressive local invasiveness rather than distant metastasis. Although complete local control was not achieved despite multimodal treatment, the 11-month postoperative progression-free interval represented clinically meaningful suppression of tumor progression, particularly when considering the rapid pattern of previous recurrences.