Collective Ectopia of All Four Ectopic Parathyroid Adenomas Clustered in the Right Cervicomediastinum: A Rare Case Report

Technical Summary: Collective Ectopia of All Four Ectopic Parathyroid Adenomas Clustered in the Right Cervicomediastinum

Problem Statement
Primary hyperparathyroidism (PHPT) is predominantly caused by a solitary parathyroid adenoma (80–85% of cases). Surgical failure in initial explorations (3–5%) is frequently attributed to ectopic gland locations or multiglandular disease. While ectopic parathyroids occur in 6–22% of persistent PHPT cases, and multiple gland diseases (e.g., double adenomas) are documented, the simultaneous occurrence of extreme ectopia involving all four parathyroid glands forming a single continuous cluster in an ectopic location has not been previously reported. This case addresses the diagnostic and surgical challenges posed by such an unprecedented anatomical anomaly, where standard anatomical expectations fail and incomplete resection leads to persistent disease.

Methodology
The study presents a detailed case report of a 32-year-old male patient with persistent PHPT following an initial resection of a right inferior parathyroid adenoma at an outside institution. The methodology involved:

1. Clinical Re-evaluation: Comprehensive laboratory assessment (PTH, serum calcium) and imaging, including cervical ultrasound, Tc-99m sestamibi imaging (MIBI), and SPECT.
2. Exclusion of Syndromes: Systematic ruling out of Multiple Endocrine Neoplasia (MEN) via adrenal function assessment, hormone level testing (calcitonin, CEA, prolactin, metanephrines), pituitary MRI, and genetic testing for MEN1.
3. Surgical Intervention: A second bilateral cervical exploration was performed via the initial incision. The surgical team conducted a thorough search of normal anatomical locations and extended exploration into the cervicomediastinum.
4. Intraoperative Monitoring: Intraoperative PTH monitoring was utilized to verify the completeness of resection.
5. Pathological Confirmation: Postoperative histopathological analysis confirmed the nature of the excised tissues.
6. Long-term Follow-up: The patient was monitored for six months post-reoperation to assess biochemical cure and parathyroid function status.

Key Results

• Anatomical Discovery: Intraoperative exploration revealed no parathyroid tissue in the four normal anatomical locations. Instead, three ectopic parathyroid adenomas were identified as a single, continuous, "grape-like" cluster. This mass originated medial to the right carotid sheath at the thoracic inlet, passed posterior to the brachiocephalic artery, and extended into the superior posterior mediastinum.
• Unification of Lesions: The authors conclude that the adenoma resected during the first surgery and the three adenomas removed during the reoperation constituted a single, contiguous ectopic complex. The initial surgery removed only the most cephalad portion of this mass.
• Biochemical Outcomes: Following the complete excision of the three remaining lesions, PTH levels dropped from 233.35 pg/mL to 6.25 pg/mL, and serum calcium decreased to 8.84 mg/dL.
• Postoperative Complication: Despite the biochemical cure of hyperparathyroidism, the patient developed permanent hypoparathyroidism, characterized by persistently low PTH and serum calcium levels requiring long-term calcium supplementation and management of recurrent cramping.
• Syndromic Exclusion: Extensive workup yielded no evidence of MEN syndromes or other hereditary endocrine disorders, though the authors note that asymmetrical involvement in such syndromes cannot be entirely ruled out.

Key Contributions

• Novel Anatomical Phenomenon: This report documents the first known case of "collective ectopia," where all four parathyroid adenomas descended en masse as a single continuous cluster in the right cervicomediastinum.
• Embryological Hypothesis: The authors propose a mechanism termed "collective ectopia," suggesting that during gestation (5–8 weeks), all four parathyroid primordia failed to segregate from one another and the descending thymus, forming a single migratory complex rather than distinct glands.
• Surgical Insight: The case highlights that in reoperative settings, a single ectopic adenoma found in an abnormal location may represent only the "tip of a contiguous iceberg." The presence of clustered or fused tracer uptake on preoperative imaging should raise suspicion for a contiguous ectopic complex rather than discrete solitary lesions.

Significance and Claims
The paper claims that this case challenges the conventional view of independent glandular migration in parathyroid embryology. It serves as a critical warning to surgeons: when preoperative imaging displays clustered tracer uptake forming a continuous lesion, a contiguous ectopic complex must be suspected. Failure to recognize this continuity can lead to incomplete resection and persistent disease. The authors emphasize that in complex reoperative cases where normal anatomical glands are absent, thorough exploration of the bilateral cervical area and superior mediastinum is essential. While the patient developed permanent hypoparathyroidism, the precise identification and complete resection of the rare clustered lesions successfully resolved the treatment-refractory hyperparathyroidism. The authors maintain a modest stance, noting that while this finding suggests an extreme failure of embryonic migration, further cases are needed to confirm the phenomenon, and long-term follow-up remains necessary to monitor for potential underlying genetic syndromes.