Eur Radiol (2005) 15: 1773–1774 DOI 10.1007/s00330-005-2676-2 LETTER TO THE EDITOR Shih-Ping Cheng Jie-Jen Lee Johnson Lin Chien-Liang Liu Received: 8 December 2004 Accepted: 30 December 2004 Published online: 12 February 2005 # Springer-Verlag 2005 Eggshell calcification in follicular thyroid carcinoma Sir, A 63-year-old woman was admitted to our hospital with gradual weakness and numbness in her left leg. A diag- nosis of essential hypertension had been made 5 years previously. On physical examination, a hard non-tender nodule was present in the right lobe of the thyroid. The remainder of the gland was palpable but not enlarged. There were no enlarged cervical lymph nodes. Cra- nial CT showed a focal osteolytic lesion involving frontal bone with epidural extension. Chest radiograph was normal except for a faint rim-like calcification in the right lower neck (Fig. 1). On thyroid function testing, the serum thy- roid-stimulating hormone level (TSH) was 0.13 mIU/l (normal range 0.50– 5.15), the thyroxine (T4) level was 3.52 ng/dl (normal range 4.4–12.5), and the triiodothyronine (T3) level was 61.1 ng/dl (normal range 100–190). Tc- 99m pertechnetate thyroid scan dem- onstrated a cold area in the right lower thyroid corresponding to the clinically palpable nodule. Ultrasound-guided fine needle aspiration cytology revealed features of follicular neoplasm. Biopsy from the skull lesion proved to be metastatic follicular carcinoma. A total thyroidectomy was performed. On gross examination, the cut surface of the resected specimen revealed a distinct yellow nodule, 2 cm in greatest diameter, located in the inferior pole of the right thyroid gland. A rim of calci- fication in the periphery was apparent (Fig. 2). Microscopically, the tumor was composed of well differentiated folli- cles with extension through the decep- tive encapsulation. Scattered foci of calcification were identified in the fi- brous stroma but no psammoma bodies were seen. The patient is currently undergoing I-131 therapy. Calcification within the thyroid gland is not uncommon, and its presence has been reported in up to 21% of plain X-rays [1]. Three distinct patterns of intrathyroidal calcification have been described: eggshell calcification, dystro- phic calcification, and fine stippled psammomatous calcification [2]. The most common is coarse dense nodular calcification, probably secondary to degenerative changes. It may occur in both benign and malignant thyroid lesions. Psammomatous calcification is presumably due to the presence of psammoma bodies, which are usually suggestive of papillary carcinoma. Eggshell calcification is infrequently seen and this type of calcification may be misinterpreted as calcified lymph nodes. Although eggshell variety is thought to be benign in nature, one case with similar calcification in association with mixed papillary and follicular thyroid carcinoma has been reported [3]. In addition, Taki and colleagues [4] recently showed that 43% of patients with eggshell calcification on ultraso- nography were associated with papillary S.-P. Cheng . J.-J. Lee (*) . C.-L. Liu Department of Surgery, Mackay Memorial Hospital, 92, Sec 2, Chung-Shan North Road, Taipei, 10449, Taiwan e-mail: surg.mmh@gmail.com Tel.: +886-2-25433535 Fax: +886-2-27233897 J. Lin Department of Hematology and Oncology, Mackay Memorial Hospital, Taipei, Taiwan