Fluorescein sodium–guided resection of cervical peripheral nerve sheath tumors in 3 dogs

Objective To describe the intraoperative findings and outcomes of fluorescein sodium-guided resection of cervical peripheral nerve sheath tumors (PNSTs) in dogs, including in the re-operative setting. Animals 3 client-owned dogs with cervical PNST. Two dogs underwent a second resection of progressive malignant PNST (MPNST) after subtotal resection and stereotactic radiation therapy performed elsewhere. One dog underwent primary resection of a previously untreated PNST identified as a schwannoma. Clinical Presentation Affected dogs were between 10 and 11 years of age (weighing between 4.2 and 5.4 kg) and presented with cervical pain, hyperesthesia, or tetraparesis. Preoperative MRI revealed contrast-enhancing intradural extramedullary masses with extraforaminal extensions. Results Fluorescein sodium (20 mg/kg) was administered IV after surgical exposure. Tumor tissue exhibited yellow discoloration under standard illumination in all dogs and bright fluorescence under 395-nm UV illumination in 2 dogs and, in the 2 re-operative cases, was visually distinct from the surrounding postoperative and radiation-induced fibrosis, which was grossly assessed as nondiseased and did not take up fluorescein. This contrast assisted dissection, and gross total resection was achieved in all dogs; nonfluorescent tissue was not biopsied. Histopathology confirmed MPNST in 2 dogs and schwannoma in 1 dog. Fluorescein-related adverse events were not observed. Both MPNST cases developed remote or metastatic disease within 4 months (1 euthanized); the schwannoma case was recurrence-free at 3 months. Clinical Relevance Fluorescein sodium–guided resection of canine cervical PNSTs is feasible with widely available equipment and may aid intraoperative identification of tumor tissue in both primary and re-operative settings, suggesting a lower equipment barrier than commonly assumed. Because nonfluorescent tissue was not sampled, fluorescein should be an adjunct to, not a substitute for, surgical judgment.