Parathyroid adenomas with pronounced lymphocytic infiltration: no evidence of autoimmune pathogenesis.

Pronounced lymphocytic infiltration in parathyroid adenoma is rare, with only six previously reported cases in the literature. The aims of this study are to review the features and investigate the pathogenesis of this rare entity. Two solitary parathyroid adenomas having this feature were reported, and the clinicopathologic features of all the documented cases were reviewed. The nature of the lymphoid infiltrate and the presence of Epstein-Barr virus (EBV) were analyzed to unveil the pathogenesis of this infiltrate. One adenoma was found in a 70-yr-old woman with primary hyperparathyroidism and valvular heart disease. The other was an autopsy finding in a 48-yr-old man who had presented with hypercalcemic crisis. The lymphoid cell population within the tumors was composed of B cells and different subsets of T cells. EBV was not detected in the infiltrates. The lymphocytic infiltrate in parathyroid adenoma is an unusual histologic entity. Its presence is unlikely to imply an autoimmune disorder. We hypothesize that the lesion may be a result of local tissue response to parathyroid adenoma.