Objective:

To report a rare case of intrathyroidal parathyroid adenoma coexisting with papillary thyroid carcinoma, emphasizing its diagnostic challenges and clinical implications.

Key Findings:

• First documented case of papillary thyroid carcinoma infiltrating an intrathyroidal parathyroid adenoma, highlighting the need for careful preoperative assessment.
• Intrathyroidal parathyroid adenomas account for less than 6% of primary hyperparathyroidism cases, indicating their rarity and diagnostic challenges.
• Fine-needle aspiration biopsy may mislead diagnosis due to cytological similarities, necessitating alternative diagnostic approaches.

Interpretation:

The coexistence of these lesions complicates preoperative diagnosis and underscores the importance of thorough histological evaluation in thyroid surgeries, impacting surgical strategies.

Limitations:

• Only a single case report, limiting generalizability and necessitating further studies to validate findings.
• Potential for misdiagnosis in similar clinical presentations, highlighting the need for increased awareness among clinicians.

Conclusion:

This case highlights critical diagnostic considerations in endocrine pathology, emphasizing the need for careful evaluation of thyroid nodules in patients with hyperparathyroidism to avoid misdiagnosis.