Molecular Characteristics of Large Parathyroid Adenomas

Tertiary hyperparathyroidism masking an atypical parathyroid tumor

Atypical parathyroid tumors represent a group of parathyroid neoplasms of uncertain malignant potential. In view of preoperative diagnostic difficulties, suspicious features for malignancy may guide the surgeon to perform a radical surgical approach.

Do large parathyroid adenomas increase the risk of severe hypercalcemia?

<b><br>Introduction:</b> Primary hyperparathyroidism (PHPT) is mainly caused by parathyroid adenoma (PA). Rare variants of PA, weighing >2.0-3.5 g are called "large" or "giant" adenomas and account for about 1.5% of all PA.</br> <b><br>Aim:</b> The aim of this study was to compare normal-sized and large parathyroid lesions identifying risk factors for severe hypercalcemia.</br> <b><br>Materials and methods:</b> 27 patients with PHPT and parathyroid lesion ≥2.0 cm3 (study group) were compared with 73 patients with PHPT and lesion < 2.0 cm³ (control group). In both groups, the majority were women (81.5% - study group, 90.5% - control group, gender ratios 4.4:9.1, respectively). The patients were examined preoperatively and postoperatively: PTH, creatine, calcium, and phosphate serum and urine concentrations, and calcidiol serum levels were assessed. Preoperative ultrasonography (US) was performed.</br> <b><br>Results:</b> Patients with larger parathyroid lesions had signifficantly higher PTH and calcium serum concentrations and lower serum phosphate and calcidiol concentrations. There were no statistically significant differences in the concentration of creatine in serum and urine, calciuria, or tubular reabsorption of phosphorus (TRP). US relatively underestimated the parathyroid volume by about 0.3-0.4 mL (10% in larger lesions and 43% in smaller ones).</br> <b><br>Conclusions:</b> Due to higher PTH and calcium levels, larger parathyroid adenomas may constitute a higher risk of severe hypercalcemia. In general, US underestimated the parathyroid volume.</br>.

Molecular and Clinical Spectrum of Primary Hyperparathyroidism

Recent data suggest an increase in the overall incidence of parathyroid disorders, with primary hyperparathyroidism (PHPT) being the most prevalent parathyroid disorder. PHPT is associated with morbidities (fractures, kidney stones, chronic kidney disease) and increased risk of death. The symptoms of PHPT can be nonspecific, potentially delaying the diagnosis. Approximately 15% of patients with PHPT have an underlying heritable form of PHPT that may be associated with extraparathyroidal manifestations, requiring active surveillance for these manifestations as seen in multiple endocrine neoplasia type 1 and 2A. Genetic testing for heritable forms should be offered to patients with multiglandular disease, recurrent PHPT, young onset PHPT (age ≤40 years), and those with a family history of parathyroid tumors. However, the underlying genetic cause for the majority of patients with heritable forms of PHPT remains unknown. Distinction between sporadic and heritable forms of PHPT is useful in surgical planning for parathyroidectomy and has implications for the family. The genes currently known to be associated with heritable forms of PHPT account for approximately half of sporadic parathyroid tumors. But the genetic cause in approximately half of the sporadic parathyroid tumors remains unknown. Furthermore, there is no systemic therapy for parathyroid carcinoma, a rare but potentially fatal cause of PHPT. Improved understanding of the molecular characteristics of parathyroid tumors will allow us to identify biomarkers for diagnosis and novel targets for therapy.

Surgical challenges of giant parathyroid adenomas weighing 10 g or more

PURPOSE

An average parathyroid adenoma (PA) weighs < 1 g. This study aimed to characterise giant PAs ≥ 10 g (GPAs) to facilitate surgical management of primary hyperparathyroidism (PHPT).

METHODS

All patients with a GPA confirmed on histology were recruited from the Monash University Endocrine Surgery Unit database. Clinical and demographic data were collected and compared to a group of non-GPA patients.

RESULTS

A total of 14 GPAs were identified between 2007 and 2018 out of 863 patients (1.6%) with a single PA excised for PHPT. The GPA patients were compared to a control group of 849 non-GPA patients in the same period with similar mean age (62 ± 16 vs 63 ± 14, P = 0.66) and gender distribution (64% vs 75% female, P = 0.35). Pre-operative calcium (Ca) and parathyroid hormone (PTH) levels were significantly higher in GPA patients (P < 0.001). A higher percentage of GPA patients (79%) had concordant localisation studies (ultrasound and sestamibi) than control patients (59%), (P = 0.13), but they were significantly less likely to undergo MIP (55% vs 82%, P = 0.02). The median GPA weighed 12.5 g (IQR 10.5-24.3). Median serum Ca normalised by day 1 post-operatively, while PTH remained elevated. Both serum Ca and PTH levels were in the normal range at 3 months. All GPA lesions were benign on histopathology.

CONCLUSION

GPAs are rare and display severe clinical and biochemical abnormalities. Despite their large size, concordant pre-operative imaging was not always achieved, and a few patients were suitable for MIP.

Parathyroid Carcinoma and Adenoma Co-existing in One Patient: Case Report and Comparative Proteomic Analysis

BACKGROUND/AIM

The lack of specific parathyroid carcinoma (PC) biomarkers in clinical practice points out the importance of analyzing the proteomic signature of this cancer. We performed a comparative proteomic analysis of PC and parathyroid adenoma (PA) co-existing in the same patient.

PATIENTS AND METHODS

PC and PA were taken from a 63-year-old patient. Using two-dimensional differential gel electrophoresis (2D-DIGE) coupled to mass spectrometry we examined the differences between PC and PA proteins. For validation, additional PC and PA samples were obtained from 10 patients. Western blot analysis was used to validate the difference of expression observed with 2D-DIGE analysis. Bioinfomatic analysis was performed using QIAGEN's Ingenuity Pathways Analysis (IPA) to determine the predominant canonical pathways and interaction networks involved.

RESULTS

Thirty-three differentially expressed proteins were identified in PC compared to PA. Among these, ubiquitin C-terminal hydrolase-L1 (UCH-L1) was highly overexpressed in PC. The result was confirmed by Western Blot analysis in additional PC samples.

CONCLUSION

Our comparative proteomic analysis of co-existing neoplasms allowed detecting specific and peculiar differences between PC and PA overcoming population biological variability.

Atypical parathyroid adenoma: clinical and anatomical pathologic features

BACKGROUND

Primary hyperparathyroidism is an endocrine pathology that affects calcium metabolism. Patients with primary hyperparathyroidism have high concentrations of serum calcium or high concentrations of parathyroid hormone, or incorrect parathyroid hormone levels for serum calcium values. Primary hyperparathyroidism is due to the presence of an adenoma/single-gland disease in 80-85%. Multiple gland disease or hyperplasia accounts for 10-15% of cases of primary hyperparathyroidism. Atypical parathyroid adenoma and parathyroid carcinoma are both responsible for about 1.2-1.3% and 1% or less of primary hyperparathyroidism, respectively.

METHODS

We performed a retrospective cohort study and enrolled 117 patients with primary hyperparathyroidism undergoing minimally invasive parathyroidectomy. Histological and immunohistochemical examination showed that 107 patients (91.5%) were diagnosed with typical adenoma (group A), while 10 patients (8.5%) were diagnosed with atypical parathyroid adenoma (group B). None of the patients were affected by parathyroid carcinoma.

RESULTS

Significant statistical differences were found in histological and immunohistochemical parameters as pseudocapsular invasion (p <  0.001), bands of fibrosis (p <  0.001), pronounced trabecular growth (p <  0.001), mitotic rates of > 1/10 high-power fields (HPFs) (p <  0.001), nuclear pleomorphism (p = 0.036), thick capsule (p <  0.001), Ki-67+ > 4% (p <  0.001), galectin-3 + (p = 0.002), and protein gene product (PGP) 9.5 + (p = 0.038).

CONCLUSIONS

Atypical parathyroid adenoma is a tumor that has characteristics both of typical adenoma and parathyroid carcinoma. The diagnosis is reached by excluding with strict methods the presence of malignancy criteria. Atypical parathyroid adenoma compared to typical adenoma showed significant clinical, hematochemical, histological, and immunohistochemical differences. We did not find any disease relapse in the 10 patients with atypical parathyroid adenoma during 60 months of follow-up time.

Using a Novel Diagnostic Nomogram to Differentiate Malignant from Benign Parathyroid Neoplasms

We sought to develop an immunohistochemical (IHC) tool to support the diagnosis of parathyroid carcinoma (PC) and help differentiate it from atypical parathyroid neoplasms (atypical) and benign adenomas. Distinguishing PC from benign parathyroid neoplasms can be challenging. Many cases of PC are histopathologically borderline for definitive malignancy. Recently, individual IHC biomarkers have been evaluated to aid in discrimination between parathyroid neoplasms. PC, atypical parathyroid neoplasms, and parathyroid adenomas treated at our institution from 1997 to 2014 were studied retrospectively. IHC analysis was performed to evaluate parafibromin, retinoblastoma (RB), protein gene product 9.5 (PGP9.5), Ki67, galectin-3, and E-cadherin expression. Receiver operating characteristic (ROC) analysis and multivariable logistic regression model for combinations of biomarkers were evaluated to classify patients as PC or atypical/adenoma. A diagnostic nomogram using 5 biomarkers was created for PC. Sixty-three patients were evaluated. The percent staining of parafibromin (p < 0.0001), RB (p = 0.04), Ki67 (p = 0.02), PGP9.5 (p = 0.04), and Galectin-3 (p = 0.01) differed significantly in the three diagnostic groups. ROC analysis demonstrated that parafibromin had the best performance in discriminating PC from atypical/adenoma; area under the curve (AUC) was 81% (cutoff, 92.5%; sensitivity rate, 64%; specificity rate, 87%). We created a diagnostic nomogram using a combination of biomarkers; AUC was 84.9% (95% confidence interval, 73.4-96.4%). The optimism-adjusted AUC for this model was 80.5% (mean absolute error, 0.043). A diagnostic nomogram utilizing an immunoexpression, a combination of immunohistochemical biomarkers, can be used to help differentiate PC from other parathyroid neoplasms, thus potentially improving diagnostic classification.

Verification of candidate microRNA markers for parathyroid carcinoma

PURPOSE

Parathyroid carcinoma (PCa) is a rare endocrine malignancy with poor prognosis and is often difficult to accurately diagnose both before and after surgery. Dysregulated microRNA (miRNA) levels have been identified in PCa using a limited number of samples. The aim of the present study was to verify a group of miRNA markers in a new series of samples to explore their potential significance in PCa diagnosis.

METHODS

A total of 58 tissue samples, including 17 PCa lesions and 41 sporadic parathyroid adenomas (PAds), were obtained from 56 primary hyperparathyroidism (pHPT) patients. Candidate miRNAs (miR-139-5p, miR-155-5p, miR-222-3p, miR-26b-5p, miR-296-5p, miR-30b-5p, miR-372-3p, miR-503-5p, miR-517c-3p, miR-7-5p, and miR-126-5p) were quantified by TaqMan real-time quantitative PCR assays.

RESULTS

Up-regulated miR-222 (p = 0.041) levels and down-regulated miR-139 (p = 0.003), miR-30b (p < 0.001), miR-517c (p = 0.038), and miR-126* (p = 0.002) levels were found in PCa relative to PAd. Binary logistic regression analysis showed that miR-139 and miR-30b were the best diagnostic markers. The combination of miR-139 and miR-30b yielded an area under the receiver operating characteristic curve of 0.888. Additionally, serum calcium (r _s  = -0.518, p < 0.001), intact parathyroid hormone (iPTH) (r _s  = -0.495, p < 0.001), and alkaline phosphatase (ALP) (r _s  = -0.523, p < 0.001) levels were negatively correlated with miR-30b levels.

CONCLUSIONS

miR-139, miR-222, miR-30b, miR-517c, and miR-126* were differentially expressed between PCa and PAd. The combined analysis of miR-139 and miR-30b may be used as a potential diagnostic strategy for distinguishing PCa from PAd.

Fine needle cytology pre-surgical differentiation of parathyroid neoplasms: Is it reliable?

BACKGROUND

Fine needle cytology (FNC) of a parathyroid neoplasia (PN) is reliable, but needs to be confirmed by Parathormone (PTH) and Thyroglobulin (TG) immunoassay on needle washing or by immunocytochemistry (ICC) evaluation. The differentiation between parathyroid adenoma (PA), atypical adenoma (PAA) and carcinoma (PC) is difficult on histology or even impossible on FNC. The aim of this study was to evaluate possible cytological criteria to classify FNC-PN further.

METHODS

Twenty-three FNC samples of PN and parathyroid cysts were rather then have been reviewed. The series includes 18 PNs, 4 cysts and 1 Thyr3B (histologically diagnosed as PA). Cytological features were: cellularity, patterns (follicular, solid or papillary), clear, oncocytic, isolated cells, nuclear atypia, cytoplasmic inclusions, nucleoli and mitoses. Data were compared with the histological controls.

RESULTS

Seventeen PNs, 2 cysts and 1 Thyr3B FNC samples were histologically diagnosed as PA (16), PAA (2) and PC (2). Two cysts and 1 PN were not confirmed histologically. Cytological features and incidences were: high cellularity (1 PA, 1 PAA, 2 PCs), follicular (8 PAs, 1 PAA), solid (5 PAs, 1 PC), papillary pattern (1PA, 1 PAA, 1 PC), clear cells (4 PAs, 1 PAA, 2 PCs), oncocytic cells (6 PAs, 1 PAA, 2 PCs), isolated cells (5 PAs, 2 PAAs, 2 PCs), nuclear atypia (2 PAs, 1 PAA, 2 PCs), cytoplasmic inclusions (4 PAs, 2 PCs), nucleoli (2 PCs) and mitoses (2 PCs).

CONCLUSION

Evident nucleoli and mitoses may suggest the differentiation between PA and PC. However, further investigations are required to confirm these preliminary observations.

Challenging neck mass: non-functional giant parathyroid adenoma

A 46-year-old man was referred to our ear, nose and throat department after the accidental discovery of a large retrotracheal mass. In order to obtain the diagnosis and to plan treatment he underwent a full battery of tests (CT, MRI, blood tests, hormonal assays, ultrasounds, thyroid scintigraphy, urine tests and fine-needle aspiration of the mass), but none of these was able to define the true nature of such cervical mass. Only after surgical excision and histological evaluation, it was diagnosed as an exceptional case of giant non-functional parathyroid adenoma.