OBJECTIVE: We sought to examine abnormal parathyroid glands for the presence of stem cells. SUMMARY BACKGROUND DATA: Cancer stem cells have been identified in cancers from a variety of tissues as a CD44/CD24 cell population. We hypothesize that stem cells (SC) may also be involved in the pathogenesis of benign clonal expansion characteristic of hyperparathyroidism (HPT). METHODS: Under institutional review board approval, parathyroid tissue was obtained from 20 patients with HPT and analyzed by fluorescence-activated cell sorting (FACS) for the CD44/CD24 cell population. Immunohistochemistry (IHC) with CD44 antibody was correlated with FACS results. RESULTS: Parathyroid tissue was obtained for FACS analysis from 25 enlarged parathyroid glands from 20 patients, 17 with primary HPT, and 3 with secondary HPT. The average percent of SC defined as CD44/CD24 population was 10.93% for enlarged parathyroid glands. IHC using CD44 antibody was performed on 27 abnormal parathyroid glands and 7 normal parathyroid gland biopsies from the same patients. Although IHC was not as sensitive as FACS, comparison of IHC and FACS results for 24 abnormal glands gave a correlation coefficient of 0.52, which was statistically significant (P = 0.01, Spearman rank). By IHC, 13 of 27 abnormal glands stained 1+ to 3+ (average, 0.93) compared with no CD44 staining in normal glands, which was statistically different (mean IHC of 0 vs. 0.93, P = 0.03, Wilcoxon). CONCLUSIONS: These novel findings demonstrate expansion of a resident cell population that expresses SC markers in abnormal parathyroid glands from patients with HPT. Our results suggest that clonal expansion of a resident SC population occurs in the pathogenesis not only of cancer, but also in benign parathyroid tumors occurring in HPT.
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