Parathyroid lipoadenomas: a rare cause of primary hyperparathyroidism

Giant parathyroid lipoadenoma case report: A parathyroid phenomenon

INTRODUCTION

Parathyroid lipoadenomas are a rare parathyroid phenomenon and an unusual cause of primary hyperparathyroidism. A difficult diagnosis to make, there are less than 100 cases in the literature since they were first described in 1958, and to our knowledge this is the largest parathyroid lipoadenoma to be reported.

PRESENTATION OF CASE

A minimally-invasive parathyroidectomy with intraoperative parathyroid hormone monitoring was performed in the case of a male with a large neck mass and symptomatic primary hyperparathyroidism. A giant parathyroid lipoadenoma was excised, with an appropriate decrease in intraoperative parathyroid hormone level observed.

DISCUSSION

This lesion poses a challenge to the surgeon, radiologist and pathologist alike and is an important addition to the scant literature available. Clinically it presents similarly to a simple adenoma. The high adipose content of this lesion leads to difficulty localising it on imaging, and the histology study can lead pathologists astray.

CONCLUSION

We highlight the importance of having the parathyroid lipoadenoma as a differential diagnosis for patients who develop primary hyperparathyroidism.

Incidentally discovered parathyroid lipoadenoma in thyroid surgery: A case report and review of the literature

Parathyroid lipoadenoma is a rare type of parathyroid adenoma, described as a single parathyroid adenoma with more than 50% fat on histologic examination and an unknown etiology, which is one of the rare causes of primary hyperparathyroidism. The difficulty of parathyroid lipoadenoma is mainly diagnosed by preoperative imaging localization. We hope to arouse attention to the parathyroid adenoma which is difficult to locate through our case report. The patient was a middle-aged male with a body mass index of 38.4 kg/m2 who admitted to our hospital with a 40-day history of an untreated thyroid nodule. We incidentally discovered parathyroid lipoadenoma in his thyroid surgery. His prognosis was good, and there were no signs of recurrence at his 12-month follow-up appointment. We believe that parathyroid lipoadenoma needs to rely on paraffin pathology to make a final diagnosis. This case report serves as a reminder that parathyroid lipoadenomas are also possible in patients who do not have primary hyperparathyroidism preoperatively and who have negative imaging. Clinicians must carefully examine the adipose tissue for the presence of parathyroid lipoadenomas during thyroid surgery to avoid postoperative hypoparathyroidism and persistent hypocalcaemia.

Surgical Aspects of Primary Hyperparathyroidism

Parathyroidectomy (PTX) is the treatment of choice for symptomatic primary hyperparathyroidism (PHPT). It is also the treatment of choice in asymptomatic PHPT with evidence for target organ involvement. This review updates surgical aspects of PHPT and proposes the following definitions based on international expert consensus: selective PTX (and reasons for conversion to an extended procedure), bilateral neck exploration for non-localized or multigland disease, subtotal PTX, total PTX with immediate or delayed autotransplantation, and transcervical thymectomy and extended en bloc PTX for parathyroid carcinoma. The systematic literature reviews discussed covered (i) the use of intraoperative PTH (ioPTH) for localized single-gland disease and (ii) the management of low BMD after PTX. Updates based on prospective observational studies are presented concerning PTX for multigland disease and hereditary PHPT syndromes, histopathology, intraoperative adjuncts, localization techniques, perioperative management, "reoperative" surgery and volume/outcome data. Postoperative complications are few and uncommon (<3%) in centers performing over 40 PTXs per year. This review is the first global consensus about surgery in PHPT and reflects the current practice in leading endocrine surgery units worldwide. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Lipoadenoma of the parathyroid: characteristics of a rare cause of hyperparathyroidism

Parathyroid Lipoadenoma (PLA) contains abundant mature adipose tissue and is a rare cause of hyperparathyroidism. This study aimed to investigate the clinical features of PLA in nine patients with primary hyperparathyroidism, including two men and seven women, with ages ranging from 45-84 years (median 60 years). PLA accounted for 0.5% of all parathyroid tumors during the study period. One patient presented with anorexia due to hypercalcemia; however, the other eight patients were asymptomatic. The median preoperative serum intact-parathyroid hormone (iPTH) and calcium levels were 143 pg/mL (range, 102-378) and 10.8 mg/dL (range, 10.3-11.3), respectively. PLA was difficult to identify using ultrasonography (US) as it appears as a moderately hyperechoic nodule and is difficult to distinguish from the surrounding adipose tissues. Only 33% of the lesions (three out of nine lesions) were accurately identified. However, they could be distinctly differentiated from the surrounding tissue using computed tomography (CT). All PLAs were also detected using the sesta-methoxyisobutylisonitrile single-photon emission-computed tomography (SPECT). All the patients were treated by a single gland extirpation. The median size and weight of the PLA were 14 mm (range, 10-22) and 567 mg (range, 200-1,533), respectively. In conclusion, the clinical manifestations of PLA are similar to those of ordinal parathyroid adenomas, except for their unique US and CT images. PLA should be considered as a potential etiologic factor in cases of hyperparathyroidism when the lesions are demonstrated as hyperechoic nodules or unidentified by US but detected by CT or SPECT imaging.

Overview of the 2022 WHO Classification of Parathyroid Tumors

The 2022 WHO classification reflects increases in the knowledge of the underlying pathogenesis of parathyroid disease. In addition to the classic characteristic features of parathyroid neoplasms, subtleties in histologic features which may indicate an underlying genetic abnormality reflect increased understanding of the clinical manifestations, histologic, and genetic correlation in parathyroid disease. The importance of underlying genetic aberrancies is emphasized due to their significance to the care of the patient. Traditionally, the term "parathyroid hyperplasia" has been applied to multiglandular parathyroid disease; however, the concept of hyperplasia is generally no longer supported in the context of primary hyperparathyroidism since affected glands are usually composed of multiple "clonal" neoplastic proliferations. In light of these findings and management implications for patient care, the 2022 WHO classification endorses primary hyperparathyroidism-related multiglandular parathyroid disease (multiglandular multiple parathyroid adenomas) as a germline susceptibility-driven multiglandular parathyroid neoplasia. From such a perspective, pathologists can provide additional value to genetic triaging by recognizing morphological and immunohistochemical harbingers of MEN1, CDKN1B, MAX, and CDC73-related manifestations. In the current WHO classification, the term "parathyroid hyperplasia" is now used primarily in the setting of secondary hyperplasia which is most often caused by chronic renal failure. In addition to expansion in the histological features, including those that may be suggestive of an underlying genetic abnormality, there are additional nomenclature changes in the 2022 WHO classification reflecting increased understanding of the underlying pathogenesis of parathyroid disease. The new classification no longer endorses the use of "atypical parathyroid adenoma". This entity is now being replaced with the term of "atypical parathyroid tumor" to reflect a parathyroid neoplasm of uncertain malignant potential. The differential diagnoses of atypical parathyroid tumor are discussed along with the details of worrisome clinical and laboratory findings, and also features that define atypical histological and immunohistochemical findings to qualify for this diagnosis. The histological definition of parathyroid carcinoma still requires one of the following findings: (i) angioinvasion (vascular invasion) characterized by tumor invading through a vessel wall and associated thrombus, or intravascular tumor cells admixed with thrombus, (ii) lymphatic invasion, (iii) perineural (intraneural) invasion, (iv) local malignant invasion into adjacent anatomic structures, or (v) histologically/cytologically documented metastatic disease. In parathyroid carcinomas, the documentation of mitotic activity (e.g., mitoses per 10mm²) and Ki67 labeling index is recommended. Furthermore, the importance of complete submission of parathyroidectomy specimens for microscopic examination, and the crucial role of multiple levels along with ancillary biomarkers have expanded the diagnostic workup of atypical parathyroid tumors and parathyroid carcinoma to ensure accurate characterization of parathyroid neoplasms. The concept of parafibromin deficiency has been expanded upon and term "parafibromin deficient parathyroid neoplasm" is applied to a parathyroid neoplasm showing complete absence of nuclear parafibromin immunoreactivity. Nucleolar loss is considered as abnormal finding that requires further molecular testing to confirm its biological significance. The 2022 WHO classification emphasizes the role of molecular immunohistochemistry in parathyroid disease. By adopting a question-answer framework, this review highlights advances in knowledge of histological features, ancillary studies, and associated genetic findings that increase the understanding of the underlying pathogenesis of parathyroid disease that are now reflected in the updated classification and new entities in the 2022 WHO classification.

Atypical primary hyperparathyroidism due to parathyroid lipoadenoma: a case report

Parathyroid lipoadenoma is a very rare cause of primary hyperparathyroidism. Preoperative imaging techniques often fail to detect such lesions, and even during surgery they can be misinterpreted just as fat tissue. A 62-year-old woman clinically monitored for primary hyperparathyroidism, with hypertension and a left nephrectomy for hydrouretheronephrosis caused by recurrent kidney stones. A neck ultrasound showed a nodule consistent with left parathyroid of 9 × 5 mm, which was not confirmed on single-photon-emission computed tomography/computed tomography (CT) scan. On surgery, a voluminous lesion with adipose appearance and texture was removed. Frozen sections and intraoperative parathyroid hormone (PTH) confirmed such lesion to be a parathyroid lipoadenoma. Parathyroid lipoadenomas are difficult to localize preoperatively. Sometimes they can be seen by ultrasound scan as hyperechoich lesion, but scintigraphy and CT often fail to identify them. Only the awareness of such lesions and the use of intraoperative PTH can avoid unnecessary extensive cervical exploration.

Parathyroid lipoadenoma: The particularities of a rare entity a case report and review of the literature

Parathyroid lipoadenoma is a rare and anusual cause of primary hyperparathyroidism. The clinical presentation usually resembles other causes of primary hyperparathyroidism and the imaging is not always contributory considering its location. However, the histologic criteria are specific. We present a case that supplements and supports the rare literature data concerning the clinical and therapeutic aspects of parathyroid lipoadenoma. The case is about a 73 years old female with a right inferior parathyroid lipoadenoma that caused biological primary hyperparathyroidism. Initially followed and treated in Rheumatology department for hypercalcemia and osteoporosis, she was sent to our structure to diagnose and possibly treat the causal etiology. After non-contributory clinical examination and ultrasound imaging, the tumor was diagnosed in the cervical CT scan. The patient underwent successful surgical removal of the lipoadenoma, confirmed postoperatively on histological analysis. The follow up showed rapid normalization of the parathormon level. Even if it's a rare condition, the diagnosis of lipoadenoma should always be considered in front of primary hyperparathyroidism with a parathyroid lesion.

Lipoadenoma of the Parathyroid Gland: Characterization of an Institutional Series Spanning 28 Years

Parathyroid lipoadenomas (PLAs) are rare tumors, and case descriptions are limited, < 80 to date. As a consequence, scarce information regarding the etiology of these enigmatic lesions is available. We searched our departmental pathology database for PLAs diagnosed between 1992 and 2020, reexamined the histology of each case, and recorded clinical parameters from the patients' medical charts. As the diagnostic criteria of this lesion vary over this time period, we defined PLA as an enlarged parathyroid gland with > 50% fat on histologic examination with preoperative evidence of primary hyperparathyroidism (PHPT). A total of 8 bona fide PLA cases and 2 equivocal PLAs (close to 50% fat) were included. As approximately 4000 conventional parathyroid adenomas were diagnosed at our department during the same time interval, the prevalence of PLA was 0.20%. PLA patients were predominately female (63%) and presented with classical PHPT-related symptoms. Majority of cases were successfully located preoperatively and had an average tumor weight of 445 mg. Histologically, all PLAs consisted of > 50% mature adipose tissue, except a single case with brown fat. Of note, PLA patients exhibited a body mass index in line with PHPT patients in general, but a relatively high, near-significant prevalence of arterial hypertension was observed when compared to tumors with less fat (P = 0.0584). Future studies on this finding might be warranted. To summarize, we present one of the largest institutional PLA case series to date, and conclude that PLAs are rare, sporadic tumors mirroring many clinical aspects of conventional adenomas-with a potential coupling to hypertension worthy of follow-up studies.

Parathyroid Pathology

Proliferative pathologic lesions of parathyroid glands encompass a spectrum of entities ranging from benign hyperplastic processes to malignant neoplasia. This review article outlines the pathophysiologic classification of parathyroid disorders and describes histologic, immunohistochemical, and molecular features that can be assessed to render accurate diagnoses.

Parathyroid Lipoadenoma: a Clinicopathological Diagnosis and Possible Trap for the Unaware Pathologist

The authors present clinicopathological features of parathyroid lipoadenoma in a 48-year-old woman who presented with symptomatic primary hyperparathyroidism manifesting with pathological fractures and osteoporosis. Preoperative sestamibi scan failed to localize the source of her disease. Exploratory surgery identified an enlarged parathyroid gland with abundant fat tissue. The significant drop of intraoperative serum parathyroid hormone after the removal of this gland and postoperative biochemical cure justified the presence of a single gland disease presenting as parathyroid lipoadenoma. From an educational perspective, the presented case emphasizes why the historical approach to parathyroid proliferations by assessing alone the ratio of parenchymal cells to adipocytes is not a reliable method in the diagnostic evaluation of parathyroid disease. While the accurate size and weight of a parathyroid gland are defining parameters of an abnormal gland, intraoperative and postoperative biochemical workup distinguishes uniglandular disease (adenoma) from multiglandular disease (hyperplasia). The authors also provide a brief review of the previously published cases of parathyroid lipoadenomas to highlight their clinicopathological characteristics of relevance to surgical pathologists.

Dynamic CT for parathyroid disease: are multiple phases necessary?

BACKGROUND AND PURPOSE

A 4D CT protocol for detection of parathyroid lesions involves obtaining unenhanced, arterial, early, and delayed venous phase images. The aim of the study was to determine the ideal combination of phases that would minimize radiation dose without sacrificing diagnostic accuracy.

MATERIALS AND METHODS

With institutional review board approval, the records of 29 patients with primary hyperparathyroidism who had undergone surgical exploration were reviewed. Four neuroradiologists who were blinded to the surgical outcome reviewed the imaging studies in 5 combinations (unenhanced and arterial phase; unenhanced, arterial, and early venous; all 4 phases; arterial alone; arterial and early venous phases) with an interval of at least 7 days between each review. The accuracy of interpretation in lateralizing an abnormality to the side of the neck (right, left, ectopic) and localizing it to a quadrant in the neck (right or left upper, right or left lower) was evaluated.

RESULTS

The lateralization and localization accuracy (90.5% and 91.5%, respectively) of the arterial phase alone was comparable with the other combinations of phases. There was no statistically significant difference among the different combinations of phases in their ability to lateralize or localize adenomas to a quadrant (P = .976 and .996, respectively).

CONCLUSIONS

Assessment of a small group of patients shows that adequate diagnostic accuracy for parathyroid adenoma localization may be achievable by obtaining arterial phase images alone. If this outcome can be validated prospectively in a larger group of patients, then the radiation dose can potentially be reduced to one-fourth of what would otherwise be administered.

A rare case of double parathyroid lipoadenoma with hyperparathyroidism

A rare case of double lipoadenomas of parathyroid glands with hyperparathyroidism is described. A 56-year-old woman was referred for management of diabetes. Work up revealed: serum Calcium (Ca) =11.9 mg/dl, glomerular filtration rate (GFR) = 103 ml/min/m2, parathyroid hormone (PTH) = 60 pg/ml, Phosphorus = 3.0 mg/dl, 25 hydroxy vitamin D (25 OH D) =16.5 ng/ml, 24 h urine Calcium =179 mg/day. Parathyroid sestamibi scan showed increased activity in the left thyroid and right thyroid lobe. Single photon emission computed tomography demonstrated uptake in inferior left and right thyroid lobes. Her serum calcium following successful bilateral parathyroidectomy was 9.3 mg/dl. Pathology showed double parathyroid lipoadenomas. After surgery, her serum Calcium and PTH normalized to 9.8 mg/dl and 32 pg/ml respectively. Lipoadenoma has been described as a very rare lesion of the parathyroid gland and is most commonly non-functional. PubMed search failed to reveal any case of hyperparathyroidism due to double parathyroid lipoadenomas.

Ectopic atypical parathyroid lipoadenoma: a rare cause of severe primary hyperparathyroidism

Parathyroid lipoadenomas are a rare and benign variant of parathyroid adenomas that are defined morphologically by an abundance of fat cells. They may be functional with secretion of parathyroid hormone or nonfunctional. We present a case of a parathyroid lipoadenoma in a patient presenting with clinical manifestations of severe primary hyperparathyroidism. Unusual features in this case included the ectopic location of the lipoadenoma in the mediastinum, the significant size of 6.6 × 3.4 cm, and weight of 30.1 g. In addition to the large size of this generally benign type of parathyroid neoplasm, histologic findings included focal band-forming fibrosis compatible with the diagnosis of an atypical parathyroid adenoma. In conclusion, this case illustrates a difficult case of an ectopic functioning parathyroid lipoadenoma with chronic sequelae due to severe hyperparathyroidism.

Tc-99m sestamibi parathyroid imaging in a rare case of parathyroid lipoadenoma

Parathyroid lipoadenoma is an unusual cause of primary hyperparathyroidism. Only a few earlier reports have documented parathyroid imaging in diagnostic studies of parathyroid lipoadenoma. Our case was a 27-year-old man, who was originally diagnosed with primary hyperparathyroidism. He underwent a Tc-99m sestamibi dual-phase parathyroid imaging study, which revealed a right-inferior parathyroid hyperfunctional lesion. The first operation removed a lesion of 1.5 cm in diameter in the area, and parathyroid lipoadenoma was diagnosed by pathology. However, hypercalcemia persisted. One week later, a Tc-99m sestamibi whole-body scan and another dual-phase imagining were performed, which demonstrated a residual lesion in the inferior part of the right thyroid region, while no ectopic lesion was found. A second surgery was performed and pathological diagnosis was confirmed as parathyroid lipoadenoma again. Our case demonstrated that although hyperfunctional parathyroid lipoadenoma is rare, Tc-99m sestamibi parathyroid imaging is reliable in locating the lesion for surgical purposes. And Tc-99m sestamibi imaging is useful in reoperative and persistent hyperparathyroidism situations as well.

Parathyroid lipoadenomas and lipohyperplasias: clinicopathologic correlations

Parathyroid lipoadenomas and lipohyperplasias are rare histologic variants with both an increase in stromal fat and parenchyma. We report the most comprehensive single institution series of lipoadenomas and lipohyperplasias to date and review the literature. Eight lipoadenomas and 3 lipohyperplasias (27 y period) were reviewed. The mean age was 60.3 years (range: 50 to 77 y) with a female predilection (1.75:1). The most common symptoms on presentation were fatigue (55.6%) and bone/joint pain (44.4%). Only 1 patient was euparathyroid. Ultrasound localized lipoadenomas in 50% of tested cases whereas sestamibi was successful in 71.4%. Despite increased stromal fat (median: 50%), the weight and the appearance of large, occasionally nodular expansions of parathyroid parenchyma within the fatty stroma distinguished lipoadenomas and lipohyperplasias from normal parathyroid tissue; none of the cases were misclassified as normal on frozen section. Mean weight for lipoadenomas was 1553 mg (range: 173 to 4587 mg), whereas the mean weight for lipohyperplasia glands was 389.1 mg. Variant morphologies included follicular patterned, oxyphil predominant, and thymic elements (thymolipoadenoma). In 1 lipohyperplasia case, not all glands were involved. Oil Red O stains showed decreased intracytoplasmic lipid in most cases. Median follow-up was 9.2 months (range: <1 to 51 mo). Only 1 lipohyperplasia patient had persistent hypercalcemia, but was asymptomatic. Lipoadenomas and lipohyperplasias are clinically similar and as histologically diverse as their conventional counterparts. Lipoadenomas are more difficult to localize preoperatively by imaging. Despite the potential difficulty at frozen section, accurate weight documentation and recognition of key histologic features diminish this challenge.