Purpose: Parathyroid carcinoma is a rare pathology, representing approximately 0.5% to 5% of all parathyroid tumours. In very minute cases, it may develop within an intrathyroidal parathyroid gland, a rare developmental anomaly. Differentiating between a thyroid nodule and an intrathyroidal parathyroid lesion using preoperative imaging and cytology can be particularly challenging as thyroid follicular cells share similar cytomorphological features with parathyroid. Methods: We present the case of male patient in his 80s with a history of cutaneous melanoma and severe fatty liver disease who underwent evaluation for a suspicious hepatic lesion. Ultrasound guided FNA and ultimately right hemithyroidectomy uncovered an atypical intrathyroidal parathyroid neoplasm. Result: Given that the PET-avid nature of the nodule and indeterminate cytology, the patient underwent a right hemithyroidectomy and parathyroidectomy with central neck dissection. The decision was based on the indeterminate cytology, FDG-avid nature of the nodule, and patient preference following MDT review. Histopathology revealed thyroid nodule consistent with an atypical intrathyroidal parathyroid neoplasm, arising within the parathyroid gland, with some features raising concern for atypia but without definitive evidence of carcinoma. Conclusion: This case underscores the diagnostic value and complexity of incidental findings on PET-CT in cancer surveillance. It also demonstrates the rare occurrence of an atypical intrathyroidal parathyroid neoplasm, discovered through the workup of a presumed thyroid lesion. A multidisciplinary approach remains crucial in evaluating indeterminate nodules, especially in patients with a background of previous skin cancer and severe liver problems.