Endocrine Abstracts

Background: Osseous metaplasia (OM) of the thyroid parenchyma and intrathyroidal mature bone formation present rare findings in the pathological evaluation of resected thyroid specimens. Graves’ disease is the most common cause of hyperthyroidism and thyrotoxicosis, is mostly characterized by diffuse enlargement of the thyroid gland and occasionally features nodular lesions with a variable percentage of malignant transformation. Herein, we present the case of a female patient with Graves’ disease and concomitant diffuse calcifications of the left thyroid lobe with a cytological suspicion of malignancy that turned out histopathologically as benign lesions with osseous metaplasia.

Case report: A 44-year-old female patient presented for endocrinological evaluation due to newly detected hyperthyroidism. The patient reported weight loss of 10 Kg over the past 3 months with persistent heart palpitations, sweating and fatigue. The neck ultrasound revealed an enlarged thyroid gland and an echomorphological pattern typical of autoimmune thyroiditis with diffuse heteroechogenicity and inhomogeneity accompanied by elevated blood flow. The left thyroid lobe featured an area with diffuse micro- and macrocalcifications in the middle zone, as well as a nodular structure with peripheral microcalcifications in the caudal zone (EU-TIRADS V). The laboratory evaluation showed a hyperthyroid state with an active thyroid autoimmunity in terms of elevated anti-TPO autoantibodies, as well as TRAb-titers suggestive of Graves’ disease. The patient was started on thyrostatic medication with methimazole 15 mg daily combined with propranolol 10 mg thrice daily. Biochemical euthyroidism was restored in 16 weeks and the methimazole dose was progressively reduced to a maintenance dosage of 2,5 mg daily 9 months after diagnosis. A fine needle aspiration biopsy of the above calcified zones was performed which showed cytological findings suspicious for malignancy (Bethesda class V). An adjunctive ultrasound of the tracheal lymph nodes revealed no pathological findings. The patient underwent total thyroidectomy, and the histological examination revealed a benign adenomatous nodule with a maximum diameter of 1,1 cm with osseous metaplasia and ectopic bone tissue formation. The patient remained euthyroid under levothyroxine supplementation needing no extra therapeutical procedures postoperatively.

Conclusion: The above case presentation comprises the first official report of osseous metaplasia and ectopic bone formation of the thyroid parenchyma in terms of Graves’ disease in Greece. The clinical significance of thyroid ossification should be further investigated as the cases are scarce in the literature. Nevertheless, pathologists should be aware of this rare phenomenon when assessing thyroid specimens with calcified areas harboring a preoperative suspicion for malignancy, as this benign histopathological diagnosis excludes further curative measures for the thyroidectomized patient.