Parathyroid involvement in thyroid cancer: an unforeseen event

Papillary Thyroid Cancer Metastases to the Parathyroid Gland

Introduction:

Papillary Thyroid cancer (PTC) is the most common malignancy encountered by endocrine surgeons accounting for up to 85% to 90% of all thyroid malignancies. Parathyroid metastases appear to be an uncommon phenomenon however are likely to be underdiagnosed due to routine parathyroid gland preservation during thyroidectomy.

Case:

We present the case of 63-year-old lady with PTC metastases to the parathyroid gland. She underwent total thyroidectomy, central compartment lymph node dissection and selective left neck (levels IIA-IV) lymph node dissection. Final pathology confirmed a 45 mm low grade conventional type papillary carcinoma with microscopic extension into perithyroidal soft tissue focally and into the adjacent left parathyroid gland.

Conclusion:

Parathyroid gland thyroid cancer infiltration/metastasis is rarely reported and likely underdiagnosed. This is the first case of parathyroid gland metastasis reported from New Zealand or Australia to our knowledge. There is currently limited research available to guide whether parathyroid gland infiltration or metastasis is of clinical or prognostic significance and whether a more aggressive treatment strategy is warranted when present.

Metastases to the Parathyroid Glands: A Comprehensive Literature Review of 127 Reported Cases

Metastases to the head and neck organs are uncommon, potentially representing the initial presentation of an occult malignancy. Single case reports and small series report metastases to the parathyroid gland, but there is no large review of the literature on secondary tumors involving the parathyroid glands. A review of the English literature between 1950 and 2017 was performed of all metastases or secondary involvement of the parathyroid glands. One hundred and twenty-seven cases of metastatic tumors were reported, although potentially significantly unrepresented in autopsy series (parathyroid glands are not routinely examined) and due to reporting bias. Women were affected more commonly than men (5.8:1; 99 vs. 17, respectively), with a mean age at presentation of 58.5 years, when reported. The most common primary sites of malignancies that metastasized to the parathyroid glands were breast carcinomas (66.9%, n = 85), melanoma (11.8%, n = 15), and lung carcinoma (5.5%, n = 7), with carcinomas representing 86.6% of metastases. Metastases were nearly always identified as part of widely metastatic disease, with only five (3.2%) cases reported as isolated metastases. Tumor-to-tumor metastases comprised 5.5% of all metastases to the parathyroid glands (metastases to parathyroid adenoma). A significant clinical finding of metastases to the parathyroid glands was the development of deranged calcium homeostasis, well beyond the 9 (7.2%) cases with primary parathyroid gland disease present. Although concurrent conditions (renal disease; bone metastases) may partially affect calcium metabolism, the onset of calcium derangement seemed to coincide with parathyroid gland metastases and not systemic disease. In summary, metastases to the parathyroid glands are uncommon, potentially under-recognized in patients who have otherwise widely metastatic tumors. Women are affected more often than men, with breast carcinomas (66.9%) and melanoma (11.8%) the most common primary tumors. Calcium homeostasis is affected, probably as a result of parathyroid gland parenchymal destruction.

Primary and metastatic parathyroid malignancies: a rare or underdiagnosed condition?

OBJECTIVE

Parathyroid gland malignancies are considered rare. The most common of these tumor types is primary parathyroid carcinoma. Metastatic spread from other cancers may also occur with up to 10% of cancers from other sites showing parathyroid involvement at autopsy. Tumor-to-tumor metastases (metastatic spread to parathyroid neoplasm) from remote cancers to the parathyroid gland have been described.

METHODS

We did a PubMed literature review and analysis of our own experience of 392 consecutive parathyroidectomies.

RESULTS

Primary and secondary parathyroid malignancies can be grouped into three categories: primary parathyroid carcinoma (PPCa), spread of carcinoma into parathyroid glands by contiguous extension from the thyroid gland or other head and neck cancer, and metastatic disease to the parathyroid gland from distant cancers. Studies of tumor-to-tumor spread indicate a predilection of spread to endocrine tumors possibly because of the rich blood supply that is present in endocrine tumors. Two of our 392 parathyroidectomies (0.5%) had cancer: one metastatic (thymic neuroendocrine tumor) and another PPCa.

CONCLUSION

Metastatic disease to the parathyroid gland is poorly documented. When performing surgery for primary thyroid cancer, the search for parathyroid gland metastases is often overlooked because of the desire to preserve parathyroid function. Metastatic disease from other cancers to a benign parathyroid gland or to a parathyroid adenoma probably suggests a grave prognosis because it likely indicates widespread metastatic disease; however, isolated metastases to the parathyroid may occur. Although these lesions may be uncommon they may not be as rare as once thought.

Parathyroid gland involvement by thyroid cancer: results from a large series of thyroidectomies performed in two italian university hospitals and review of the literature

Objectives.Parathyroid involvement by thyroid cancer (TC) has not been frequently investigated in thyroidectomy-based studies. We aimed to detect cases of parathyroid invasion by TC in a large series of thyroidectomies and to review the literature on this topic. Study Design. A 10-yr period database research was made from the files of the Section of Pathology of two Italian University Hospitals. Out of 22,310 thyroidectomies, 10 patients with parathyroid involvement by TC were found. Results. The 10 patients, 7 females and 3 males, aged 55 ± 14 years (range 34-76, median 56) had papillary thyroid carcinoma and accounted for 0.4% of subjects affected by all TCs and submitted to thyroidectomy. The tumor invaded perithyroid soft tissues in 6 patients and central neck (level VI) lymph nodes in 3. Parathyroid involvement by TC occurred by infiltration in 6 cases, extension through an intervening pseudocapsule in 1, and both patterns in 3. All patients are alive and disease free at 5.6 ± 3-yr follow-up. Conclusion. Limited to thyroidectomy series, our results and literature data suggest that parathyroid involvement by TC has a 0.4-3.9% incidence rate; mainly affects women in their sixth-seventh decade of life; is associated to a good prognosis, unless massive extrathyroid extension of TC occurs.