Expression of Parafibromin in Distant Metastatic Parathyroid Tumors in Patients with Advanced Secondary Hyperparathyroidism Due to Chronic Kidney Disease

Cohort review of patients with parathyroid cancer in End Stage Renal Disease (ESRD)

BACKGROUND AND HYPOTHESIS

Parathyroid carcinoma (PTTC) is a rare malignant endocrine tumor seen in up to 1-2% of all cases of primary hyperparathyroidism. However, incidence of parathyroid carcinoma in renal hyperparathyroidism is a rare phenomenon. We aimed to evaluate the outcomes of PTTC in renal hyperparathyroidism published in the literature.

METHODS

Cohort review of parathyroid cancer cases reported in Medline (via PubMed), COCHRANE and EMBASE between the period 1985 - 2023 in patients with renal hyperparathyroidism.

RESULTS

A total of 48 patients (20 M: 28F), with a mean age of 49.8 (± 11.7 SD: range 20-75) years. Dialysis vintage was for a period of 8.9 (± 7.2; range 6 months to 40 years). The mean preoperative values were as follows: serum corrected calcium-2.87 IQR 2.56-3.01), PTH - 221.8 (IQR 86.6 -257.2 pmol/L) and serum phosphate - 2.07 (IQR 1.72-2.28) mmol/L. Preoperative imaging was in the form of ultrasound of the neck in 21 of 48 (44%), MIBI scan in 27/48 (56%), contrast enhanced computerized tomography in 14/48 (29%) and MRI neck in 1/48 (2%). The mean size of the cancer was 2.7 (± 1.35) cm and weight of the gland ranged between 0.9 to 4.98 g. 18/48 (37%) patients underwent a total parathyroidectomy and 30/48 (63%) had subtotal parathyroidectomy. En bloc excision of the tumour along with the thyroid along and central compartment lymph nodes was only performed in 12/48 (25%), of whom 9 (19%) had it performed at index surgery, whereas in the rest was done for persistent or recurrent disease. After a mean follow up of 34 months, 14 (29%) had local recurrence, 1 (2%) had distant metastasis to the skeletal system, and 12 (25%) to the lungs. Cohort mortality was 6 (13%) due to refractory hypercalcemia.

CONCLUSIONS

Parathyroid carcinoma in renal hyperparathyroidism is rare but when encountered, en bloc excision with parathyroidectomy provides the best chance of cure. Recurrences can be difficult to treat but may be needed to treat intractable hypercalcaemia.

Parathyroid carcinoma in chronic renal disease - a case series of three patients and review of literature

BACKGROUND

Apart from being a rare endocrine tumor, parathyroid carcinoma is also one of the rarest malignancies in human beings. Parathyroid carcinoma is even more uncommon in haemodialysis patients with end-stage renal disease. The pathogenesis of parathyroid hyperplasia in haemodialysis patients is well known, but the mechanism of development of parathyroid carcinoma in these patients remains unclear.

METHODS

Three cases of parathyroid carcinoma in haemodialysis patients are presented in this study: a 69-year-old male patient and two female patients (67 and 61 years old). In all cases parathyroid carcinoma infiltrated the ipsilateral thyroid lobe and in one patient the right laryngeal nerve was involved as well. One patient underwent three surgical procedures.

RESULTS

After surgical treatment, all patients were normocalcaemic and showed a significant reduction in PTH levels.

CONCLUSION

In patients with secondary hyperparathyroidism, who develop parathyroid carcinoma, surgical resection is the only viable treatment option.

Immunohistochemical Profile of Parathyroid Tumours: A Comprehensive Review

Immunohistochemistry remains an indispensable tool in diagnostic surgical pathology. In parathyroid tumours, it has four main applications: to detect (1) loss of parafibromin; (2) other manifestations of an aberrant immunophenotype hinting towards carcinoma; (3) histogenesis of a neck mass and (4) pathogenetic events, including features of tumour microenvironment and immune landscape. Parafibromin stain is mandatory to identify the new entity of parafibromin-deficient parathyroid neoplasm, defined in the WHO classification (2022). Loss of parafibromin indicates a greater probability of malignant course and should trigger the search for inherited or somatic CDC73 mutations. Aberrant immunophenotype is characterised by a set of markers that are lost (parafibromin), down-regulated (e.g., APC protein, p27 protein, calcium-sensing receptor) or up-regulated (e.g., proliferation activity by Ki-67 exceeding 5%) in parathyroid carcinoma compared to benign parathyroid disease. Aberrant immunophenotype is not the final proof of malignancy but should prompt the search for the definitive criteria for carcinoma. Histogenetic studies can be necessary for differential diagnosis between thyroid vs. parathyroid origin of cervical or intrathyroidal mass; detection of parathyroid hormone (PTH), chromogranin A, TTF-1, calcitonin or CD56 can be helpful. Finally, immunohistochemistry is useful in pathogenetic studies due to its ability to highlight both the presence and the tissue location of certain proteins. The main markers and challenges (technological variations, heterogeneity) are discussed here in the light of the current WHO classification (2022) of parathyroid tumours.

Immunohistochemistry in Diagnostic Parathyroid Pathology

Pathologists are usually readily able to diagnose parathyroid tissues and diseases, particularly when they have knowledge of the clinical information, laboratory findings, and radiographic imaging studies. However, the identification of parathyroid tissue or lesions can be difficult in small biopsies, ectopic locations, supranumerary glands, and in some oxyphil/oncocytic lesions. Widely available immunohistochemical studies such as chromogranin-A, synaptophysin, keratin, parathyroid hormone, thyroglobulin, and thyroid transcription factor-1 can help in difficult cases. One of the most difficult diagnostic aspects faced by the pathologist in evaluating parathyroid is distinguishing between parathyroid adenoma, particularly atypical adenoma, and parathyroid carcinoma. Many markers have and continue to be evaluated for diagnostic utility, and are even beginning to be studied for prognostic utility. Single immunohistochemical markers such as parafibromin and Ki-67 are among the most studied and most utilized, but many additional markers have and continue to be evaluated such as galectin-3, PGP9.5, Rb, bcl2, p27, hTERT, mdm2, and APC. Although not widely available in many laboratories, a panel of immunohistochemical markers may prove most useful as an adjunct in the evaluation of challenging parathyroid tumors.

The surgical management of renal hyperparathyroidism

Secondary and tertiary hyperparathyroidism (HPT) develop in patients with renal failure due to a variety of mechanisms including increased phosphorus and fibroblast growth factor 23 (FGF23), and decreased calcium and 1,25-dihydroxy vitamin D levels. Patients present with various bone disorders, cardiovascular disease, and typical laboratory abnormalities. Medical treatment consists of controlling hyperphosphatemia, vitamin D/analog and calcium administration, and calcimimetic agents. Improved medical therapies have led to a decrease in the use of parathyroidectomy (PTX). The surgical indications include parathyroid hormone (PTH) levels >800 pg/ml associated with hypercalcemia and/or hyperphosphatemia despite medical therapy. Other indications include calciphylaxis, fractures, bone pain or pruritis. Transplant recipients often show decreased PTH, calcium and phosphorus levels, but some will have persistent HPT. Evidence suggests that PTX may cause deterioration in renal graft function in the short-term calling into the question the indications for PTX in these patients. Pre-operative imaging is only occasionally helpful except in re-operative PTX. Operative approaches include subtotal PTX, total PTX with or without autotransplantation, and possible thymectomy. Each approach has its proponents, advantages and disadvantages which are discussed. Intraoperative PTH monitoring has a high positive predictive value of cure but a poor negative predictive value and therefore is of limited utility. Hypocalcemia is the most common complication requiring aggressive calcium administration. Benefits of surgery may include improved survival, bone mineral density and alleviation of symptoms.

Parathyroid tumors and related disorders

Primary hyperparathyroidism (P-HPT) is a common endocrine disorder that occurs as a result of adenomas (80-85%), hyperplasias (10-15%) or carcinomas (<1%) of the parathyroid glands. Molecular genetic analyses of heritable P-HPT syndromes have provided considerable insight into the understanding of sporadic parathyroid tumors and hyperplasias. This review will focus on the criteria for classification of parathyroid proliferative disorders and will highlight our understanding of these lesions at the molecular level. Advances in radiological imaging techniques together with the rapid intraoperative parathyroid hormone assay will be reviewed with respect to current treatment approaches for P-HPT.

Parathyroid cancer

Parathyroid cancer is an uncommon malignancy and rare cause of primary hyperparathyroidism (HPT) with a high morbidity and patient death in advanced cases usually resulting from intractable hypercalcemia. Inactivation of the HRPT2/CDC73 gene, encoding the putative tumor-suppressor protein parafibromin and discovered in the context of the hyperparathyroidism-jaw tumor (HPT-JT) syndrome, is a common, somatic event in most parathyroid cancers. Approximately 25% of patients with apparently sporadic parathyroid cancer carry germline HRPT2/CDC73 mutation. Germline DNA analysis for HRPT2/CDC73 mutation is recommended in all patients with parathyroid cancer because of the potential benefit for first-degree relatives, who should nevertheless undergo serum calcium screening. The histopathologic diagnosis of parathyroid cancer is nonspecific unless vascular, lymphatic, capsular, or soft tissue invasion is seen, or metastases are clinically evident. Immunohistochemical analysis of parathyroid tumors for loss of parafibromin expression offers promise as a diagnostic tool. En bloc tumor resection offers the highest chance of cure in patients with suspected parathyroid carcinoma. No adjuvant chemotherapy regimen has yet proven effective, and the role of local adjuvant radiotherapy is being evaluated. Metastatic disease can be palliated with surgical debulking. Medical therapy with the calcimimetic cinacalcet and bisphosphonates can ameliorate hypercalcemia in patients with inoperable disease.

Removal of autografted parathyroid tissue for recurrent renal hyperparathyroidism in hemodialysis patients

BACKGROUND

Recurrent renal hyperparathyroidism (HPT) is a serious problem after parathyroidectomy (PTx). We evaluated the frequency of graft-dependent recurrent HPT and the clinical outcomes after removal of the autograft.

METHODS

Between March 1980 and January 2009, 2660 patients underwent total PTx with forearm autograft. After resection of all parathyroid glands, 30 pieces of 1 x 1 x 3 mm parathyroid tissue from diffuse hyperplasia, if possible, were autografted into brachioradial muscle. Graft-dependent recurrence of HPT was diagnosed by a high PTH gradient and detection of swollen autografts by palpation and/or MRI or US.

RESULTS

In 248/2660 (9.3%) patients, removal of the graft was required a total of 327 times (53 patients required removal of the autograft several times). The cumulative frequency of graft-dependent recurrent HPT was 17.4% ten years after the initial PTx. Thirty-two patients underwent both resection of missed glands located in the neck or mediastinum and removal of the graft. En-bloc resection of autograft with surrounding muscle was required to avoid reoperation. When the intact PTH level dropped under 300 pg/ml, in the majority of patients renal HPT could be medically managed after the operation. The mean weight of the resected parathyroid tissue was 1583.7 mg. No specimen had histopathologically malignant features. Three patients suffered from hematoma in the wound.

CONCLUSIONS

Graft-dependent recurrent renal HPT is not negligible. However, in the majority of patients, renal HPT can be controlled by removal of the autograft noninvasively. Total PTx with forearm autograft is preferable for hemodialysis patients, especially when long-term survival is expected.

Parafibromin as a diagnostic instrument for parathyroid carcinoma-lone ranger or part of the posse?

The diagnosis of parathyroid carcinoma requires an invasive growth pattern or metastases detected at histopathological examination; unfortunately, not all carcinomas exhibit visible malignant properties at the initial assessment. Therefore, immunohistochemical markers have been sought for the recognition of parathyroid malignancy. In 2003, the Hyperparathyroidism 2 (HRPT2) gene was found mutated in the majority of sporadic parathyroid carcinomas investigated, and studies regarding the protein product parafibromin proposed loss of nuclear parafibromin as a highly sensitive marker for the detection of parathyroid carcinoma. Recent studies have not fully reproduced these findings, as subsets of carcinomas display positive parafibromin immunoreactivity, and fractions of adenomas demonstrate absent expression. Overall, parafibromin is a marker of value to the endocrine pathologist, but it cannot be recommended as a sole indicator of parathyroid carcinoma. Additional markers such as protein gene product 9.5 (PGP9.5) and adenomatous polyposis coli (APC) could complement parafibromin when assessing malignant potential of parathyroid tumours.

[Indication and performance of endocrine surgery. The significance of molecular genetic examination]

The molecular genetic changes from certain endocrine tumors are already understood, reflecting as they do the etiology of these sporadic familial disorders. This already has clinical consequences to the treatment of familial endocrine tumors, which often appear in the course of syndromatic disorders. These consequences consist in slight changes to surgical technique, the search for other active and usually endocrinal tumors, and examination of family members for other gene carriers (of disease-specific mutations) and the most suitable prophylactic tumor therapy. In contrast, for sporadic endocrine tumors there exists far less clinically relevant knowledge. Starting with anamnesis and clinical findings of active endocrine tumors, we discuss the current possibilities for molecular genetic determination of disease-specific mutations (germline and tumor DNA) and their effect on surgical procedure.

Challenging lesions in the differential diagnosis of endocrine tumors: parathyroid carcinoma

Parathyroid neoplasms encompass a spectrum of proliferative lesions that include adenomas, atypical adenomas, and carcinomas. While the diagnosis of adenomas is usually straightforward, parathyroid carcinomas (PTCAs) often present considerable diagnostic challenges. Fibrosis and mitotic activity are common in PTCAs, but these features are not specific for malignancy. An unequivocal diagnosis of PTCA should be restricted to those tumors that invade adjacent soft tissues, thyroid gland, blood vessels, or perineural spaces or to those cases with documented metastases. Atypical adenomas include those tumors that share some of the features of PTCA but lack evidence of invasive growth. A variety of genetic abnormalities, including HRPT2 mutations, occur in PTCAs. Mutations of the HRPT2 gene, which encodes parafibromin, are responsible for the development of the hyperparathyroidism-jaw tumor syndrome and have also been implicated in the development of a high proportion of sporadic PTCAs. Correlative immunohistochemical studies have revealed nuclear parafibromin immunoreactivity in adenomas but absence or partial loss of staining in PTCAs. While parafibromin immunohistochemistry represents an important step in the ability to diagnose PTCA, additional studies will be required to test the validity of this approach and to determine the roles of other genes in the development of these tumors.