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Outcomes from excision of parathyroid carcinomas
A D VA N C E S
death associated with PTC was a dog that was euthanized for intractable hypocalcemia 9 days after surgery. Estimated 1-, 2- and 3-year survival rates were 72, 37, and 30%, respectively.
Author Conclusion Excision of PTC results in resolution of hypercalcemia and excellent tumor control.
Inclusions Two figures, 5 tables, 22 references.
Editor Annotation
OUTCOMES FROM EXCISION OF PARATHYROID CARCINOMAS Background Parathyroid carcinomas (PTCs) arise from parathyroid hormone (PTH)-producing chief cells, resulting in unregulated secretion of PTH and resultant hypercalcemia. PTCs are rare in dogs, representing 4 to 10% of parathyroid nodules in dogs with primary hyperparathyroidism (PHPT). When present, clinical signs are due to hypercalcemia and mimic signs associated with PHPT caused by the more common causes, parathyroid hyperplasia or adenoma. As a result, concern for malignancy is not prompted by clinical presentation alone.
Objectives To describe the outcome of dogs with PTC treated with surgical excision.
Procedure Medical records of 19 dogs undergoing surgical excision of PTC were reviewed retrospectively. Dogs were presented for clinical hypercalcemia or incidental hypercalcemia noted by referring veterinarians on routine serum chemistry profiles.
Results A parathyroid nodule was identified with cervical ultrasonography in all 17 dogs. Hypercalcemia resolved in 18 of the 19 dogs within 4 days postoperatively. Nine developed hypocalcemia. None developed recurrent or metastatic PTC. The only
Canine parathyroid carcinoma is described much less commonly than parathyroid adenoma or hyperplasia. This study’s results reveal that PTC is most likely in older dogs, and associated clinical signs are often non-specific (i.e., weakness, lethargy, and anorexia). All dogs in this study were hypercalcemic, and PTH concentrations were elevated or inappropriately normal in all cases where they were assayed. Likewise, a parathyroid nodule was seen on ultrasonography in all dogs where this study was performed. Clinical outcome was excellent after surgical resection alone, with resolution of hypercalcemia and a median survival time of 614 days. Neither local recurrence nor metastasis was documented in any of the dogs. The most common complication was post-operative hypocalcemia, which was life-threatening in some cases. Based on this study, veterinarians managing dogs who may have PTC should perform routine serum biochemistry with ionized calcium and PTH levels, along with cervical ultrasonography, to tentatively confirm the diagnosis. Cervical exploratory for tumor resection should be performed in a 24-hour facility with the ability to closely monitor post-operative serum calcium concentrations and provide instantaneous treatment if hypocalcemia develops. Finally, it is worthwhile to note that this study provides yet another example of a situation where routine screening blood work performed in what is apparently a relatively normal older animal may yield important and potentially life-saving information. (GEM) Sawyer ES, Northrup NC, Schmiedt CW, et al. Outcome of 19 dogs with parathyroid carcinoma after surgical excision. Vet Comp Oncology 2011;10:57-64.
PAG E 7
death associated with PTC was a dog that was euthanized for intractable hypocalcemia 9 days after surgery. Estimated 1-, 2- and 3-year survival rates were 72, 37, and 30%, respectively.
Author Conclusion Excision of PTC results in resolution of hypercalcemia and excellent tumor control.
Inclusions Two figures, 5 tables, 22 references.
Editor Annotation
OUTCOMES FROM EXCISION OF PARATHYROID CARCINOMAS Background Parathyroid carcinomas (PTCs) arise from parathyroid hormone (PTH)-producing chief cells, resulting in unregulated secretion of PTH and resultant hypercalcemia. PTCs are rare in dogs, representing 4 to 10% of parathyroid nodules in dogs with primary hyperparathyroidism (PHPT). When present, clinical signs are due to hypercalcemia and mimic signs associated with PHPT caused by the more common causes, parathyroid hyperplasia or adenoma. As a result, concern for malignancy is not prompted by clinical presentation alone.
Objectives To describe the outcome of dogs with PTC treated with surgical excision.
Procedure Medical records of 19 dogs undergoing surgical excision of PTC were reviewed retrospectively. Dogs were presented for clinical hypercalcemia or incidental hypercalcemia noted by referring veterinarians on routine serum chemistry profiles.
Results A parathyroid nodule was identified with cervical ultrasonography in all 17 dogs. Hypercalcemia resolved in 18 of the 19 dogs within 4 days postoperatively. Nine developed hypocalcemia. None developed recurrent or metastatic PTC. The only
Canine parathyroid carcinoma is described much less commonly than parathyroid adenoma or hyperplasia. This study’s results reveal that PTC is most likely in older dogs, and associated clinical signs are often non-specific (i.e., weakness, lethargy, and anorexia). All dogs in this study were hypercalcemic, and PTH concentrations were elevated or inappropriately normal in all cases where they were assayed. Likewise, a parathyroid nodule was seen on ultrasonography in all dogs where this study was performed. Clinical outcome was excellent after surgical resection alone, with resolution of hypercalcemia and a median survival time of 614 days. Neither local recurrence nor metastasis was documented in any of the dogs. The most common complication was post-operative hypocalcemia, which was life-threatening in some cases. Based on this study, veterinarians managing dogs who may have PTC should perform routine serum biochemistry with ionized calcium and PTH levels, along with cervical ultrasonography, to tentatively confirm the diagnosis. Cervical exploratory for tumor resection should be performed in a 24-hour facility with the ability to closely monitor post-operative serum calcium concentrations and provide instantaneous treatment if hypocalcemia develops. Finally, it is worthwhile to note that this study provides yet another example of a situation where routine screening blood work performed in what is apparently a relatively normal older animal may yield important and potentially life-saving information. (GEM) Sawyer ES, Northrup NC, Schmiedt CW, et al. Outcome of 19 dogs with parathyroid carcinoma after surgical excision. Vet Comp Oncology 2011;10:57-64.
PAG E 7