Resumen de Partial resection of the hyoid apparatus during surgical treatment of ectopic thyroid carcinomas in dogs: 5 cases (2011–2013)
Objective—To assess perioperative findings and postoperative complications and outcomes in dogs that had ectopic thyroid carcinomas with invasion into the hyoid apparatus and underwent tumor excision with partial hyoidectomy.
Design—Retrospective case series.
Animals—5 client-owned dogs.
Procedures—Medical records of dogs that had an ectopic neuroendocrine tumor with invasion into the hyoid apparatus and underwent tumor excision with partial hyoidectomy were reviewed for information regarding perioperative and postoperative findings and outcome. During surgery in each case, the thyrohyoid and ceratohyoid or epihyoid bones (depending on degree of hyoid apparatus involvement) were sharply transected, allowing en bloc removal of the tumor. The ipsilateral cut ends of the thyrohyoid and ceratohyoid or epihyoid bones (depending on which was cut) were sutured together with polypropylene suture in a simple interrupted pattern.
Results—All partial hyoidectomy procedures were completed without surgical or anesthetic complications. All 5 dogs were able to eat and drink between 7 and 24 hours after surgery, with no signs of dysphagia, ptyalism, or abnormal tongue carriage. Follow-up information was obtained over a period of 173 to 587 days after surgery for all 5 dogs; 4 dogs were still alive at last follow-up. One dog was euthanized 587 days after surgery because of lethargy, inappetence, and hypercalcemia.
Conclusions and Clinical Relevance—From this limited series of cases, results suggested that partial resection of the hyoid apparatus during removal of ectopic thyroid carcinoma may be tolerated well and be associated with very good functional outcomes in dogs. (J Am Vet Med Assoc 2014;245:1319–1324) Ectopic thyroid tissue is common in dogs, being present in nearly half of adult canine cadavers.1 Ectopic tissue results from rapidly proliferating islets of the thyroid primordia, which separate from the main mass of developing tissue and become incorporated into the structures of the branchium and thorax.2 Neoplasms of ectopic thyroid tissue are considered relatively rare in dogs, compared with other neoplasms, and such tumors develop in the thoracic cavity more commonly than in the cervical region.3 For dogs, resection of orthotopic thyroid carcinoma is the current standard of care, when determined to be feasible without excessive risk or long-term patient morbidity.3,4 The notion that thyroid carcinomas in ectopic locations, such as at the base of the tongue, are not amenable to surgical removal exists both anecdotally and within the peer-reviewed veterinary medical literature.5 Degree of invasion into surrounding structures and resultant loss of mobility of the primary tumor are often used to assess resectability.4 Additional information obtained with the use of advanced 3-D imaging techniques, such as CT or MRI, allows further evaluation of tumor invasiveness and potential for surgical excision.6 Because of their ectopic location, thyroid tumors in the cranial cervical region of the body may involve portions of the hyoid apparatus, resulting in relative tumor immobility and reluctance of surgeons to operate. This reluctance arises out of concerns regarding postoperative morbidity resulting from resection of anatomic structures involved with the tumor and leads to pursuit of alternative treatment options such as external beam radiation therapy.3,4 To the authors' knowledge, the only peer-reviewed publication that addresses resection of cervical ectopic thyroid tumors in dogs was a report by Lantz and Salisbury7 published in 1989; the report described 3 dogs, all of which had tumor invasion into the hyoid apparatus. Given the paucity of information and the advances in perioperative patient management since publication of that report, the objective of the study reported here was to describe perioperative findings and postoperative complications and outcomes in dogs that had cervical ectopic thyroid carcinomas with invasion into the hyoid apparatus and underwent tumor excision and partial resection of the hyoid apparatus. A secondary objective was to describe a variation in the surgical technique for partial hyoidectomy in present use, compared with the historically described method.7
