Microsatellite instability in sporadic parathyroid adenoma

Parathyroid adenomas are usually benign uniglandular tumors, and inactivati on of several tumor suppressor genes, notably the MEN 1 gene, or activation of oncogenes have been implicated in the tumorigenesis. Genomic instabilit y, indicative of the involvement of DNA mismatch repair genes, has not been previously described in parathyroid adenomas. A single large parathyroid a denoma was resected from an 8.5-yr-old Brazilian patient with no personal o r family history of other endocrinopathies. Analysis of paired tumor-nontum or DNA using 23 microsatellite markers, located on chromosomes 1, 10, and 1 1 was carried out. Microsatellite instability was detected in nine markers (D1S191, D1S212, D1S413, D1S2848, RET, D11S901, D11S903, INSR, and INT2), w hereas no allelic loss was detected with any of the analyzed markers. Immun ohistochemical analysis of retinoblastoma protein expression revealed low l evels of expression, but no histopathological signs of malignancy. We concl ude that in this single, apparently sporadic parathyroid adenoma, DNA misma tch repair genes might be involved in parathyroid tumorigenesis.