Suspected Iatrogenic Seeding of Oral Melanoma Secondary to Endotracheal Intubation in a Dog.

A 10 yr old castrated male pug was presented with a 3 day history of intermittent dyspnea, cough, inappetence, and inability to breathe while sleeping. He had previously received hypofractionated radiation therapy for an amelanotic oral malignant melanoma (OMM) 7 mo prior to presentation. At presentation, the dog was gasping and dyspneic. Oral examination identified the OMM on the right hard palate. Thoracic radiographs revealed an angular soft-tissue opacity within the trachea just distal to the thoracic inlet. No evidence of pulmonary metastatic disease was seen. Tracheoscopy identified a pedunculated, nonpigmented mass within the lumen of the distal trachea near the carina. Treatment options were presented to the owners and included tracheal stenting or tracheal resection and anastomosis. Because of the poor prognosis, the owners elected humane euthanasia. Postmortem examination confirmed the presence of melanoma in the distal trachea; no other sites of OMM metastasis were identified. The cause of OMM development in the distal trachea in this case is suspected to have resulted from mechanical tumor cell seeding during endotracheal tube placement for general anesthesia 7 mo prior to presentation. Despite the reported rarity of mechanical tumor seeding, this potential complication warrants consideration in dogs with OMM.