Papillae formation in parathyroid adenoma. A source of possible diagnostic error

Parathyroid adenomas, the most common cause of hyperparathyroidism, display diverse histologic patterns. The majority of adenomas form solid masses or show nodular, trabecular, and acinar patterns. In a four-year review of data on 103 surgically resected parathyroid adenomas, we encountered only a single case that showed papillae formation. We report this case to illustrate occurrence of this unusual histologic pattern that might create a diagnostic problem.