AACE Clinical Case Reports Rapid Electronic Articles in Press Rapid Electronic Articles in Press are preprinted manuscripts that have been reviewed and accepted for publication, but have yet to be edited, typeset and finalized. This version of the manuscript will be replaced with the final, published version after it has been published in the print edition of the journal. The final, published version may differ from this proof. DOI:10.4158/EP161436.CR © 2016 AACE.

Case Report

EP161436.CR BROWN TUMORS AND THE ATYPICAL PARATHYROID ADENOMA

Junao Wang MD1, Paari Murugan MD2, Khalid Amin MD2, Elizabeth Seaquist MD3, Lisa Chow MD,MS3 From: 1PGY-1 Resident, University of Minnesota Medical School, 420 Delaware Street SE, MMC 293, Minneapolis, MN 55455; 2Department of Laboratory Medicine and Pathology, University of Minnesota, 420 Delaware St SE, MMC 76 Mayo, Minneapolis, MN 55455; 3 Division of Endocrinology, Diabetes and Metabolism, University of Minnesota, 420 Delaware St SE, MMC 101 Mayo, Minneapolis, MN 55455

Running Title: Case Report: Atypical parathyroid adenoma

Correspondence address: Lisa Chow, MD Division of Endocrinology, Diabetes and Metabolism University of Minnesota 420 Delaware St SE, MMC 101 Minneapolis, MN 55455 E-mail: [email protected]

DOI:10.4158/EP161436.CR © 2016 AACE.

Disclosure Statement: The authors have nothing to disclose.

Key terms: Parathyroid Adenoma, Parathyroid Carcinoma, Brown tumor, Hyperparathyroidism; Hypercalcemia Word count: Abstract: 250 Body: 1500 Number of figures and tables: 4

DOI:10.4158/EP161436.CR © 2016 AACE.

ABSTRACT Objective: Present a case of an atypical parathyroid adenoma with extreme clinical features and discuss the uncertainties in differentiating between benign and malignant masses. Method: The clinical, laboratory, and imaging findings are presented with a literature review of current methods for distinguishing parathyroid adenoma from carcinoma. Result: A 37-year old man presented to his primary care physician with worsening bone pain and increasing irritability over the span of 2 years. Laboratory evaluation showed a highly elevated serum calcium (15.7 mg/dL) and parathyroid hormone (1790 pg/mL). Computed tomography revealed multiple brown tumors throughout his body and a 2.8cm mass in the tracheoesophageal groove. Fine needle aspiration of the 2.8 cm mass was suggestive of a neoplastic/hyperplastic process but could not definitively identify thyroid or parathyroid cells. The patient underwent surgery 2 weeks after initial diagnosis. Because intraoperative histopathology was suggestive of parathyroid adenoma, simple parathyroidectomy was performed. The final pathology report, however, demonstrated atypical features that were suggestive but not diagnostic of parathyroid carcinoma. The patient was ultimately given a diagnosis of atypical parathyroid adenoma but continues to be monitored for signs of malignancy. Conclusion: Parathyroid adenoma and carcinoma differ greatly in their disease progression and standard of care. Fine needle aspiration should be avoided if high clinical suspicion for a parathyroid mass. While histopathology is the mainstay for differentiating between parathyroid adenoma and carcinoma, it may fall short for tumors with ambiguous features. Literature review suggests that immunohistochemistry may be an increasingly valuable tool in differentiating between benign and malignant parathyroid masses.

DOI:10.4158/EP161436.CR © 2016 AACE.

INTRODUCTION Primary hyperparathyroidism is the third most common endocrine disorder and is the most common cause of hypercalcemia in an outpatient setting.1 Since the introduction of serum calcium assays in the 1970s, it has largely been an incidental finding on routine laboratory studies.2 Patients rarely present initially with brown tumors: reactive, osteolytic lesions which are considered to be the end-stage skeletal manifestation of primary hyperparathyroidism.3 Discovery of lytic bone lesions in association with elevated parathyroid hormone should elicit a differential which includes parathyroid adenoma and carcinoma. However, the distinction between adenoma and carcinoma is not always clear. This presents a dilemma to physicians as surgical management and clinical outcomes differ between these two disease processes. CASE REPORT A 37-year old man presented to his primary care physician with bone and joint pain, increasing irritability, and 10-pound weight loss over 2 years. More recently, the pain became severe enough to require crutches for ambulation. Prior to onset of symptoms, he had not seen a doctor in nearly a decade. His past medical history was significant for essential hypertension and a kidney stone 10 years earlier. Family history was significant for hypertension. On physical examination, blood pressure was elevated at 154/94, and stiffness was noted in the left leg. Neck exam did not reveal any goiters or other abnormalities. The remainder of the exam was normal. On workup, laboratory testing revealed an elevated serum calcium of 15.7 mg/dL (normal 8.510.5 mg/dL). Patient was admitted to an outside hospital. Further testing identified multiple abnormalities, most notably a serum parathyroid hormone of 1790 pg/mL (range 14.5-87.1 pg/mL) (Table 1). Sestamibi scan did not reveal any parathyroid adenomas. A neck ultrasound did not show evidence of parathyroid adenoma, but it did show a focal, ovoid, 1.1 x 0.3 x 0.7 cm hypoechoic nodule in the left DOI:10.4158/EP161436.CR © 2016 AACE.

thyroid lobe. Computed tomography was performed, which revealed a 2.8 cm mass in the right neck base near the thyroid gland. Additionally, there were multiple non-obstructing intrarenal calculi in both kidneys and lytic, expansile skeletal lesions on the ribs, pelvis, and proximal femurs bilaterally. Notably, the left femoral lesion occupied the majority of the medullary canal and appeared at risk for an impending fracture (Figure 1). Given these findings, the leading diagnosis was hypercalcemia and brown tumor secondary to parathyroid adenoma or carcinoma. A diagnosis of multiple endocrine neoplasia was briefly entertained, but this was thought to be unlikely given normal prolactin and calcitonin levels, unremarkable urine catecholamines, and absence of acromegaly (Table 1). Similarly, multiple myeloma was ruled out by serum immuofixation. Fine needle aspiration was performed on the neck mass identified on computed tomography to assess for malignancy. While cytology showed increased cellularity suspicious for a neoplastic or hyperplastic process, the cells could not be definitely identified as parathyroid cells. Furthermore, fine needle aspiration was also performed on the thyroid nodule identified on ultrasound, and histopathology was suggestive of a benign colloid nodule. Following stabilization, the patient was transferred to our care with plan for parathyroidectomy and possible right thyroid lobectomy. During surgical exploration, a parathyroid gland was identified deep in the tracheoesophageal groove. Although some fibrotic components were present, the gland was relatively easy to excise. The excised gland weighed 4.7g, measured 3.6 x 2.5 x 1.4cm, and showed no features suggestive of malignancy on limited sampling of frozen sections. Two nearby lymph nodes were also excised, which showed no metastatic disease. Therefore, lobectomy was not performed. The intraoperative parathyroid hormone level rapidly dropped following gland excision (Table 2). Final pathology revealed focal areas of infiltration into the pericapsular soft tissue, a single focus highly suspicious for perineural invasion, and rare areas of necrosis. However, most of the tissue appeared bland with no evidence of dense fibrosis, spindled cells, or vascular invasion (Figure 2). Furthermore, the DOI:10.4158/EP161436.CR © 2016 AACE.

Ki-67 proliferation index was low at 1-2%. While the tumor exhibited some worrisome characteristics, an overt diagnosis of parathyroid carcinoma could not be rendered, and instead, the patient was given the diagnosis of atypical parathyroid adenoma. In the days following surgery, hungry bone syndrome developed, requiring vitamin D and calcium supplementation. By four weeks post-surgery, serum calcium had normalized, and some of the lytic bone lesions had demonstrated partial remineralization (Table 2). By two months, the patient was able to ambulate without the assistance of a crutch. As of September 2016 (22 months post-surgery), the patient has received no further surgical intervention. He continues to be monitored closely for signs of hyperparathyroidism given the concerning histological features. DISCUSSION As hypercalcemia is increasingly identified as an incidental finding on laboratory testing, clinical presentations of severe hypercalcemia with brown tumors are becoming increasingly rare.4 The presented case is novel given that the clinical severity and parathyroid tumor size are suggestive of parathyroid carcinoma, yet the histology and tumor markers were not clearly consistent with a parathyroid carcinoma. This ambiguity in parathyroid tumor classification warrants a discussion of methods to distinguish benign versus malignant masses. Comparison of Clinical Features Parathyroid adenomas represent 80-85% of cases of primary hyperparathyroidism and are curable with simple parathyroidectomy.5 In contrast, parathyroid carcinomas account for 1-5% of cases and require en-bloc resection because they may recur. Furthermore, they can metastasize both lymphatically and hematogenously, with common sites including lung (40%), cervical lymph nodes (30%), and liver (10%).6 Despite this, parathyroid carcinomas are frequently approached as adenomas in practice. According to the Surveillance, Epidemiology, and End Results cancer registry, approximately 76.8% of DOI:10.4158/EP161436.CR © 2016 AACE.

parathyroid carcinomas were treated via simple parathyroidectomy from 1988 to 2003.7 When managed inappropriately via simple parathyroidectomy compared to en-bloc resection, the 5-year recurrence risk is 56% higher.8 Pathological Features of Parathyroid Adenoma vs Carcinoma Diagnosis of parathyroid carcinoma requires presence of vascular invasion, perineural invasion, extra-capsular infiltration, and/or metastases.9 Borderline adenomas that show some overlapping features with parathyroid carcinomas are sometimes described as atypical parathyroid adenomas. One comparison study found that increased mitotic figures, capsular adherence, coagulative necrosis, higher weight, and larger size were associated with carcinomas as opposed to atypical adenomas.10 Theories exist that atypical parathyroid adenomas are actually low-grade carcinomas, but these atypical adenomas have generally remained benign on 2-year follow-up after local excision.9 Unfortunately, long-term follow-up remains lacking in literature. No Role for Fine Needle Aspiration Generally, fine needle aspiration is unhelpful in distinguishing between parathyroid adenomas and carcinomas as more than 80% of parathyroid carcinomas remain well-differentiated. In addition, isolated cases of capsule rupture and tumor seeding have been reported11, and the procedure may lead to fibrotic reactions that mimic malignancy in appearance, furthering complicating surgery and marring a histologic diagnosis.12 In our case, fine needle aspiration provided little diagnostic value, and it is uncertain whether procedure contributed to the pathologic findings of focal fibrosis and infiltration. While the parathyroid hormone level of the aspirate could have been measured to at least confirm the presence of a parathyroid lesion, this was not performed. Leveraging Immunohistochemistry

DOI:10.4158/EP161436.CR © 2016 AACE.

There is increasing interest in applying immunohistochemistry to aid in differentiating parathyroid tumors. Unfortunately, individual markers have high inter-study variability. For instance, loss of parafibromin staining, the best known marker for parathyroid carcinoma, was found to have sensitivities ranging between 29 to 100%. However, its specificity appeared reliable, ranging between 95 to 100%. Some studies have demonstrated better sensitivity by using a panel of immunohistochemical markers. Although the sensitivity for individual markers may be low, using multiple markers with high specificities would theoretically increase overall sensitivity without significantly increasing false positives. This was demonstrated by Truran et al. in a small study that combined antibodies directed against parafibromin, PGP9.5, Galectin-3, and Ki-67 and demonstrated 79% sensitivity and 100% specificity.13 Another small study demonstrated 80% sensitivity and 100% specificity for parathyroid carcinomas by testing for combined loss of parafibromin and Rb staining.14 In a larger study that reviewed 267 neoplasms, a panel combining parafibromin, Gal-3, and PGP9.5 demonstrated 50% sensitivity and 97.9% specificity for parathyroid carcinoma.15 As a caveat, the overall sample size of these studies are small, and intraoperative utility may be limited by the incubation time required for some of these stains. Nevertheless, the panels may help guide clinicians in determining which cases should return to the operating room for additional resection. Conclusion Although histopathology is the mainstay for differentiating parathyroid adenoma and carcinoma, our case demonstrates the practical challenges of this approach. On one hand, the bland appearance, easy dissection, unremarkable lymph nodes, lack of dense fibrosis, and absence of mitotic figures all contributed to a picture of a benign process. On the other, the foci of tissue infiltration, perineural invasion, and necrosis all represent worrisome features. With a final diagnosis of atypical parathyroid adenoma, the patient is subjected to years of watchful waiting, with minimal reassurance from literature that additional lesions will not develop. Preliminary work has shown that immunohistochemical panels DOI:10.4158/EP161436.CR © 2016 AACE.

can diagnose parathyroid carcinoma with moderate sensitivity and high specificity. Though promising, many of these studies are derived from small sample sizes, and more research needs to be conducted to see if the results are applicable and cost-effective for the population at large.

REFERENCES 1. DeLellis, RA. Parathyroid tumors and related disorders. Modern Pathology 2011;S78-S93. 2. Walker MD, Rubin M, Silverberg SJ. Nontraditional manifestations of primary hyperparathyroidism. J Clin Densitom 2013;16:40-7. 3. Raeburn CD, Cothren C, McIntyre RC. End-stage skeletal manifestations of severe hyperparathyroidism. Surgery 2002;132:896-8. 4. Wermers RA, Khosla S, Atkinson EJ, et al. Incidence of primary hyperparathyroidism in Rochester, Minnesota, 1993-2001: an update on the changing epidemiology of the disease. J Bone Miner Res 2006;21:171-177. 5. Marcocci C, Cetani F. Primary Hyperparathyroidism. N Engl J Med 2011;365:2389-95. 6. Shane E. Clinical review 122: Parathyroid carcinoma. J Clin Endocrinol Metab 2001;86:485-93. 7. Lee PK, Jarosek SL, Virnig BA, et al. Trends in the incidence and treatment of parathyroid cancer in the united states. Cancer 2007; 1;109:1736-41. 8. Talat N, Schulte KM. Clinical presentation, staging and long-term evolution of parathyroid cancer. Ann Surg Oncol 2010;17:2156-74. 9. IARC. Pathology and genetics of tumours of endocrine organs. 1st ed. World Health Organization; 2004. 10. Quinn CE, Healy J, Lebastchi AH, et al. Modern experience with aggressive parathyroid tumors in a high-volume New England referral center. J Am Coll Surg. 2015;220:1054-62.

DOI:10.4158/EP161436.CR © 2016 AACE.

11. Wei CH, Harari A. Parathyroid carcinoma: Update and guidelines for management. Curr Treat Options Oncol 2012;13:11-23. 12. Norman J, Politz D, Browarsky I. Diagnostic aspiration of parathyroid adenomas causes severe fibrosis complicating surgery and final histologic diagnosis. Thyroid 2007;17:1251-5. 13. Truran PP, Johnson SJ, Bliss RD, et al. Parafibromin, galectin-3, PGP9.5, Ki67, and cyclin D1: Using an immunohistochemical panel to aid in the diagnosis of parathyroid cancer. World J Surg 2014 ;38:2845-54. 14. Erovic BM, Harris L, Jamali M, et al. Biomakers of Parathyroid Carcinoma. Endocr Pathol 2012;23: 221-231. 15. Kumari N, Chaudhary N, Pradhan R, et al. Role of Histological Criteria and Immunohistochemistry Markers in Predicting Risk of Malignancy in Parathyroid Neoplasms. Endocr Pathol 2016;27:87-96.

DOI:10.4158/EP161436.CR © 2016 AACE.

Laboratory Test Serum *Calcium (mg/mL) *Phosphorous (mg/dL) *Parathyroid hormone (pg/mL) *Vitamin D (ng/mL) Calcitonin (pg/mL) Creatinine (mg/dL)

Measured

Reference Range 15.7 1.3 1790 11.7