Tıp Araştırmaları Dergisi: 2011 :9 (1) :53 -55
T AD
ARAŞTIRMA
A huge thyroid nodule inconsistent with scintigraphic findings Ismail Dogan 1 , Irfan Nuhoglu2 , Bircan Sonmez1 , Aysegul Cansu3 , Kadriye Yıldız4 1
Department of Nuclear Medicine, KTU, Faculty of Medicine, Trabzon, Turkey 2 Department of Endocrinology, KTU, Faculty of Medicine, Trabzon, Turkey 3 Department of Radiology, KTU, Faculty of Medicine, Trabzon, Turkey 4 Department of Pathology, KTU, Faculty of Medicine, Trabzon, Turkey
Abstract Warm (normoactive) thyroid nodules are extremely rare compared to the cold or hot nodules. The management of these cases is similar to the cold nodules. They can grow and seldom enlarge involving up to the whole lobe. We present a case of nodular guatr located in the right lobe presenting discordant characteristics in thyroid scintigraphy with Tc99m pertechnetate and radioiodine. Key Words: Warm nodule, discordant nodule, Tc99m pertechnetate, radioiodine
Uyumsuz sintigrafik bulgular gösteren büyük tiroid nodülü
Özet Ilık (normoaktif) tiroid nodülleri, soğuk ve sıcak nodüllerle kıyaslandığında çok daha nadirdir. Bu nodüllerin takibi soğuk nodüllerinkine benzerdir.
Bunlar nadiren bir lobu kaplayacak boyutlara kadar büyüyebilirler. Tc99m perteknatat ve radyoiyotla yapılan tiroid bezi sintigrafilerinde uyumsuz karakter gösteren sağ lobda lokalize nodüler guatrlı bir vaka sunuyoruz. Anahtar Kelimeler: Ilık nodül, diskordan nodül, Tc99m perteknetat, radyoiyot
Introduction Tc99m pertechnetate is widely used in thyroid scintigraphic imaging. This agent is actively taken into the thyroid gland by active transport but its organification does not take place. Based on these basic properties, this protocol differs from the use of radioiodine (I-131 and I-123) which has a rarer use for thyroid scintigraphy. The use of Tc99m pertechnetate and radioiodine generally provide similar results. But in some cases, though rarely, their results can be different (1-5). Majority of the nodules showing normoactivity on Tc99m pertechnetate scintigraphy, cannot organify iodine (3-5). Therefore it needs to be differentiated from malignancy (5).
Correspondence:
Case
Dr. Ismail Dogan. Karadeniz Technical University Medical Faculty, Department of Nuclear Medicine 61080 Trabzon / TURKEY. Phone: (+90) 462 377 57 34. Fax: (+90) 462 377 57 42. e-mail:
[email protected]
A 60 years old male patient was admitted with a swelling on his neck for the last couple of years. The physical examination of the neck revealed a palpable solitary nodule in the right lobe of thyroid gland. On the laboratory examination, thyroid function tests documented euthyroid; free T3:3.59 ng/dl, (normal 1.8-4.6),
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free T4:1.0 ng/dl (normal 0.9-1.7) and thyroidstimulating hormone (TSH):3.04 μIU/mL (normal 0.27-4.2).
containing cystic degenerative changes and macrocalcification ( Fig. 1). Color- flow doppler sonography indicated marked peripheral and minimal internal vascularity (not shown). 5mCi Tc99m pertechnetate scintigraphy revealed a normoactive nodule involving the whole lobe. (Fig. 2). Imaging 24 h after oral administration of 50 uCi I-131, the nodule placed in the right lobe had characteristics of cold nodule (Fig. 3). Uptake in the remainder of the thyroid gland was normal. Total right lobectomy were carried out. Histopathologic examination revealed nodular colloidal goiter (Figure 4). The postoperative course was uneventful.
Figure 1. Ultrasound image shows a large predominantly solid mass containing both cystic and solid areas.
Figure 3. Imaging 24 h after oral administration of 50 uCi I-131, the right lobe placed nodule was in nature of cold nodule characteristics.
Figure 2. Tc99m pertechnetate scintigraphy were performed 30 min after injection of radioactivity. It was revealed a normoactive nodule involving the whole lobe. Uptake in the remainder of the thyroid gland was normal.
On sonogram, right thyroid lobe was 60 x 40 x 30 mm and left thyroid lobe was 32 x 14 x 12 mm in diameter. There was a well- defined predominantly solid nodule (46 x 43 x 27 mm) on the right lobe which had a mixed pattern
Figure 4. The large follicular structures were filled with colloid and lined by a chronic inflammatory infiltrate with large eosinophilic thyroid cells (Hematoxylen-Eosin x100).
55 Dogan ve ark.
Discussion The pertechnetate ion becomes trapped only in the follicular cells and, unlike iodine, does not become organified or incorporated into thyroid hormone. This may account for discordant Tc99m pertechnetate and I-131 imaging. Despite this rare discrepancy, Tc99m is the commonly used isotope for functional evaluation in the routine practice due to low cost and easy availability in Europe (1) . Conflicting results between Tc99m pertechnetate accumulation and radioiodine incorporation in thyroid gland nodules, regarding functional status of the nodule occuring in about one in thirty patients have been reported (1, 2). In most of these cases the nodules were not warm (normoactive) but hot (hyperactive) character and usually do not occupy the whole lobe in the Tc99m pertechnetate scintigraphy. However, by using the radioiodine, most of the discordant nodules observed as cold nodules. Detection of hyperactivity by radioiodine among these discordant nodules is very rare (3-5). The majority of the discordant nodules that can accumulate Tc99m pertechnetate but not radioiodine are thought to have organification defects. The active transport and organification capacities of the cells at the periphery of the nodules are normal. The failure of organification results from the loss of function in the medially located cells (2). Non-palpable normoactive (or warm) thyroid gland nodules, cannot be detected scintigraphically because of their small size or localization. As seen in our case, this type of nodules can rarely enlarge to occupy the whole lobe but remain as normoactive. These nodules can be associated with the carcinoma, adenomatous guatr or follicular adenomas (2, 5). Warm nodules constitute about 10% to 15% of all
nodules with less than 10% of reported malignancy (1). Especially, if they do not supress the TSH, the warm nodules are likely to be discordant and therefore carries a probabilty of malignancy (4, 5). Management of these nodules should be the same as those of cold nodules (1, 5). In conclusion, the scintigraphic imaging done by using Tc99m may not reflect the true character of the nodules. Therefore, even the nodules were classified as warm or hot, in case of clinical suspicion or in the presence of circulating thyrotropin (TSH) within the normal range, further investigations are recommended.
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