Adjuvant Therapy with Imatinib for an Incompletely Resected Multilobular Tumour of Bone in a Dog

A 5-year-old neutered male Shiba Inu dog presented with a history of oral bleeding, dysphagia, and depression for 3 weeks. The physical examination revealed a firm mass in the right caudal palatal region along the level of PM4-M2. On the computed tomography, the mass was round-to-oval in shape and 22 mm × 30 mm × 15 mm in size. The mass contained multiple bone attenuated materials with a palatal bone lysis of 4 mm × 6 mm. A complete resection of the mass was proposed; however, the owner declined due to the risk of complications associated with the radical surgery. Therefore, a palliative resection and biopsy of the mass were performed. On the histological examination, the mass was diagnosed as grade 2 multilobular tumour of bone (MTB). Since the mass was incompletely resected, adjuvant therapy was pursued along with targeted therapy using a tyrosine kinase inhibitor. The tumour cells showed overexpression of the receptor of tyrosine kinase for c-KIT, PDGFR-α, PDGFR-β, and FGFR1 compared to normal tissue cells. Additionally, the cytotoxic effect of imatinib on the MTB cells was confirmed in vitro. Four weeks postoperatively, the administration of imatinib and carprofen was initiated and continued for 259 days. The patient maintained a good functional outcome for 306 days after the initial presentation.