Because of the close anatomical location to the thyroid gland, invasion of the thyroid may occur, though rarely reported.
Because of the intimate involvement of calcium regulation employed by the parathyroid gland (produces parathyroid hormone), calcium homeostasis is disrupted by excessive synthesis and secretion of parathyroid hormone, resulting in clinical hyperparathyroidism and hypercalcemia (normal range 1.91 - 3.03 mmol/L) are commonly observed in affected dogs.
Diagnosis is based on presence of a palpable parathyroid mass and ultrasonographic confirmation of neoplastic appearance to the mass.
Serum levels of both parathyroid hormone and parathyroid hormone-related protein should be assessed as levels may fluctuate with not only parathyroid carcinoma with with other non-parathyroid malignancies
Fine needle biopsy and histological analysis of sample tissues is usually definitive. Histologically, these tumors present with indistinct cell borders, high nuclear-cytoplasmic, high mitotic index and moderate anisokaryosis and anisocytosis, with occasional binucleated cells and megalocytes.
A differential diagnosis would include hyperparathyroidism, parathyroid adenoma, parathyroid hyperplasia, hypercalcemia of malignancy (anal sac adenocarcinoma, multiple myeloma and osteosarcoma), chronic renal disease, hypoadrenocorticism and vitamin D toxicosis.
Parathyroidectomy is usually curative although hypocalcemia is a common post-operative complication requiring calcium and vitamin D supplementation. In some cases postsurgical rehabilitation of c
Recurrences or metastases are very rare.
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