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

Parathyroid Imaging: Past, Present, and Future

The goal of parathyroid imaging is to identify all sources of excess parathyroid hormone secretion pre-operatively. A variety of imaging approaches have been evaluated and utilized over the years for this purpose. Ultrasound relies solely on structural features and is without radiation, however is limited to superficial evaluation. 4DCT and 4DMRI provide enhancement characteristics in addition to structural features and dynamic enhancement has been investigated as a way to better distinguish parathyroid from adjacent structures. It is important to recognize that 4DCT provides valuable information however results in much higher radiation dose to the thyroid gland than the other available examinations, and therefore the optimal number of phases is an area of controversy. Single-photon scintigraphy with 99mTc-Sestamibi, or dual tracer 99mTc-pertechnetate and 99mTc-sestamibi with or without SPECT or SPECT/CT is part of the standard of care in many centers with availability and expertise in nuclear medicine. This molecular imaging approach detects cellular physiology such as mitochondria content found in parathyroid adenomas. Combining structural imaging such as CT or MRI with molecular imaging in a hybrid approach allows the ability to obtain robust structural and functional information in one examination. Hybrid PET/CT is widely available and provides improved imaging and quantification over SPECT or SPECT/CT. Emerging PET imaging techniques, such as 18F-Fluorocholine, have the exciting potential to reinvent parathyroid imaging. PET/MRI may be particularly well suited to parathyroid imaging, where available, because of the ability to perform dynamic contrast-enhanced imaging and co-registered 18F-Fluorocholine PET imaging simultaneously with low radiation dose to the thyroid. A targeted agent specific for a parathyroid tissue biomarker remains to be identified.

Metastatic disease in head & neck oncology

The head and neck district represents one of the most frequent sites of cancer, and the percentage of metastases is very high in both loco-regional and distant areas. Prognosis refers to several factors: a) stage of disease; b) loco-regional relapses; c) distant metastasis. At diagnosis, distant metastases of head and neck cancers are present in about 10% of cases with an additional 20-30% developing metastases during the course of their disease. Diagnosis of distant metastases is associated with unfavorable prognosis, with a median survival of about 10 months. The aim of the present review is to provide an update on distant metastasis in head and neck oncology. Recent achievements in molecular profiling, interaction between neoplastic tissue and the tumor microenvironment, oligometastatic disease concepts, and the role of immunotherapy have all deeply changed the therapeutic approach and disease control. Firstly, we approach topics such as natural history, epidemiology of distant metastases and relevant pathological and radiological aspects. Focus is then placed on the most relevant clinical aspects; particular attention is reserved to tumours with distant metastasis and positive for EBV and HPV, and the oligometastatic concept. A substantial part of the review is dedicated to different therapeutic approaches. We highlight the role of immunotherapy and the potential effects of innovative technologies. Lastly, we present ethical and clinical perspectives related to frailty in oncological patients and emerging difficulties in sustainable socio-economical governance.

Parathyroid cancer: An update

Parathyroid cancer (PC) is a rare malignant tumor which comprises 0.5-5% of patients with primary hyperparathyroidism (PHPT). Most of these cancers are sporadic, although it may also occur as a feature of various genetic syndromes including hyperparathyroidism-jaw tumor syndrome (HPT-JT) and multiple endocrine neoplasia (MEN) types 1 and 2A. Although PC is characterized by high levels of serum ionized calcium (Ca) and parathyroid hormone (PTH), the challenge to the clinician is to distinguish PC from the far more common entities of parathyroid adenoma (PA) or hyperplasia, as there are no specific clinical, biochemical, or radiological characteristic of PC. Complete surgical resection is the only known curative treatment for PC with the surgical approach during initial surgery strongly influencing the outcome. In order to avoid local recurrence, the lesion must be removed en-bloc with clear margins. PC has high recurrence rates of up to 50% but with favorable long-term survival rates (10-year overall survival of 60-70%) due to its slow-growing nature. Most patients die not from tumor burden directly but from uncontrolled severe hypercalcemia. In this article we have updated the information on PC by reviewing the literature over the past 10 years and summarizing the findings of the largest series published in this period.

Metastasis of renal cell carcinoma to the parathyroid gland 12 years after radical nephrectomy

Renal cell carcinoma (RCC) accounts for 2-3% of all malignant tumors in adults. RCC is well-known for its propensity to metastasize to unusual sites, and late metastasis, even after several years, is common. Involvement of the parathyroid gland has only four reported cases in literature. A 62-year-old Caucasian man was referred to our department due to an enlarging cervical mass. The patient's relevant past medical history included a left nephrectomy for RCC 12 years ago. After right thyroid lobectomy and isthmectomy, histopathology revealed an intrathyroidal nodule corresponding to the parathyroid gland with metastatic RCC. Approximately one-third of RCC subjects with apparently localized disease will develop metastasis, even several years after nephrectomy. The literature is sparse regarding the most appropriate follow-up approach for these patients. We describe a rare case of nodular goiter of the thyroid gland concurrent with metastatic RCC to an intrathyroidal parathyroid gland, without disseminated systemic metastasis.

Solid Cell Nests Within a Parathyroid Gland-Report of an Exceptional Case

The ultimobranchial body (UBB) denotes the cellular mass originating from the fourth branchial pouch, which migrates from the neural crest and infolds within the middle and upper poles of the thyroid lobes, thereby establishing the presence of calcitonin-secreting parafollicular C cells. In various numbers, UBB remnants (entitled "solid cell nests", or SCNs) are found in thyroid glands examined histologically. However, despite the close embryological relation between the UBB and the superior parathyroid glands, intraparathyroidal SCNs have to our knowledge not been previously reported. Here, we describe a patient presenting with a papillary thyroid carcinoma with central and lateral lymph node metastases. Upon postoperative analysis, an unintentionally removed parathyroid gland was observed adjacent to the superior aspect of the right thyroid lobe. Within a 0.6 × 0.5-mm area of the parathyroid gland, solid nests composed of epithelial cells with oval and slightly elongated nuclei were seen. The cells were positive for p40, p63, and GATA3, but negative for PTH. The final diagnosis was a SCN entrapped within the parathyroid gland. Empirically, we have not previously observed SCNs within the parathyroid glands. To our knowledge, our finding thus constitutes a very unusual histological manifestation, and could indicate an underlying aberrancy during embryogenesis given the close anatomical relationship between the UBB and the superior parathyroid glands.

A Herald of Plasma Cell Myeloma: A Report of Malignant Plasma Cells Identified in Parathyroid Adenoma and a Review of Non-parathyroid Malignancies in Parathyroid Glands

Involvement of the parathyroid glands by non-parathyroid neoplasia is an infrequent event. Rare cases of metastases to the parathyroid gland have been reported in parathyroidectomies and autopsies of patients with known solid or hematopoietic malignancies. Here, we present a case of atypical clonal plasma cells incidentally identified within a parathyroid adenoma resected for hyperparathyroidism and hypercalcemia, which served as the sentinel event for a subsequent diagnosis of plasma cell myeloma. To our knowledge, this is the only reported case of a hematopoietic malignancy involving a parathyroid adenoma and the only reported case of malignant hematopoietic cells initially detected in parathyroidectomy.