Parathyroid Pathology Uncovered: Tiny Glands, Big Questions

Parathyroid neoplasms encountered in routine practice are most often diagnostically straightforward and can usually be classified on the basis of conventional histomorphology without the need for extensive biomarker work-up. This relative simplicity has contributed to the perception that pathologic assessment of parathyroid tumors is largely uncomplicated. Yet this view rapidly changes when a lesion exhibits atypical features beyond those expected in a conventional adenoma, particularly when the differential diagnosis includes parathyroid carcinoma, an exceptionally rare but potentially fatal malignancy. In these difficult cases, the endocrine pathologist carries substantial responsibility in separating misleading and overinterpreted atypical findings from lesions that truly harbor malignant potential or an increased risk of recurrence. Beyond classification, pathology also has a central role in identifying molecular abnormalities of diagnostic or therapeutic relevance in parathyroid carcinoma, as well as recognizing morphologic or immunophenotypic clues that may point to an underlying hereditary syndrome. In some cases, the pathologist may be the first to raise suspicion of a germline disorder and thereby initiate further genetic investigation. This review provides a focused analysis of the major histopathologic challenges in primary hyperparathyroidism. Particular emphasis is placed on distinguishing ordinary adenoma from normal glands, identifying atypical parathyroid tumors and parathyroid carcinoma while avoiding overdiagnosis, integrating immunohistochemical and molecular findings into diagnostic practice, and identifying features suggestive of hereditary disease. Our aim is to provide a practical framework that supports more accurate, reproducible, and clinically relevant pathologic assessment of parathyroid tumors.