SUN-137 Clonal Status of Multigland Disease Primary Hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a common endocrine disorder that arises due to single or multiple parathyroid gland disease (MGD). The molecular mechanism(s) of parathyroid neoplasia are incompletely understood and both monoclonal (mono-X) and polyclonal (poly-X) parathyroid tumors have been described using methylation-sensitive PCR of X-linked Human Androgen Receptor (HUMARA) alleles. Our previous investigations of parathyroid tumor clonal status has shown that poly-X tumors are common and are associated with MGD in patients with non-familial PHPT (Shi et al. 2014 & 2018). This work examined the clonal status of the dominant gland and the clonal relationship of multiple tumors from the same patient has not been examined. The goal of the current study was to determine the clonal relationship of parathyroid tumors from PHPT patients with MGD. Banked parathyroid tissues from twenty-nine PHPT patients with MGD were examined in this study. Clonal status (mono-X vs poly-X) of multiple abnormal parathyroid glands from each patient was determined using a modification of the HUMARA assay used in our prior work. Briefly, methylation-sensitive PCR of HUMARA alleles was performed followed by fragment analysis using Capillary-Electrophoresis performed. Raw fragment sizing data analyzed using Peak Scanner software. Classification of samples as either mon-X or poly-X was made as described in (Shattuck et al.) Of 29 PHPT patients with MGD, 13 (45%) had pure mono-X, 5 (17%) had pure poly-X, and 11 (38%) had a mixture of mono-X and poly-X tumors. Five of 29 patients had three or more abnormal glands evaluated: 3 had mixture of poly-X and mono-X, 2 had pure mono-X tumors, and none were pure polyclonal-X. Eighteen (62%) out of 29 patients had paired upper or lower double adenomas. Of these, 9 (50%) were pure mono-X, 4 were pure poly-X, and 5 were mixed mono-X/poly-X. In 2 patients with multiple mono-X tumors, allele distribution was not the same in different abnormal glands. Our previous work has demonstrated that among patients with non-familial PHPT, poly-X parathyroid tumors are common and are associated with MGD. Our new data extend these findings to show that the clonal relationship between multiple parathyroid tumors from the same patient is complex and may reflect the emergence of single or multiple tumors from a background of parathyroid hyperplasia, or other mechanism(s). Future studies to explore the mechanisms behind these apparent clonal relationships are warranted and ongoing. Reference: (1) Shi et al., PNAS 2014, 201319742. (2) Shi et al., Surgery 2018, 9-14. (3) Shattuck. N Engl J Med 2005, 2406-12.