Ectopic parathyroid adenomas in primary hyperparathyroidism: anatomical classifications, localization strategies, and case series

Background: Ectopic parathyroid adenomas (EPAs) pose significant challenges in the diagnosis and management of primary hyperparathyroidism (PHPT) due to their atypical locations. This study aims to categorize EPAs based on their anatomical locations, describe the associated diagnostic strategies, and present case studies to illustrate clinical management. Methods: EPAs were retrospectively reviewed based on cases from published literature and our institutional experience. Relevant studies were identified through a systematic search of PubMed and Embase. A comprehensive anatomical classification system was developed, categorizing EPAs into pharyngocranial, cervical, and mediastinal regions. Results: From a total of 1,278 screened publications, 137 studies encompassing 875 EPAs were identified and included. Combined with 13 original cases from our institute, these cases were comprehensively analyzed to develop an anatomically based classification system. EPAs were categorized into four types based on anatomical location: Type I (Pharyngocranial), Type II (cervical, adjacent to the thyroid), Type III (cervical, distant from the thyroid), and Type IV (mediastinal). A combination of imaging modalities, including ultrasonography, CT, MRI, sestamibi scintigraphy, and SPECT, proved effective for preoperative localization. Case studies highlight clinical outcomes and challenges associated with each type. Conclusion: A comprehensive anatomical classification system for EPAs, integrated with advanced imaging modalities and correlated with biochemical profiles, improves preoperative identification and guides targeted treatment strategies.