Scintigraphic and ultrasonographic appearance in different tumor stages ofthyroid carcinoma

Rationale and objectives. Scintigraphy is routinely used in evaluating thyr oid nodules. Functioning nodules are reported to have a low probability of being malignant. Therefore cancer should appear hypofunctioning or "cold" o n scintiscan. The aim of the study was to compare the scinitgraphic pattern in different tumor stages of thyroid carcinoma. In addition, sonographic r esults are evaluated. In 151 patients with thyroid carcinoma Tc-99m-pertechnetate scans were eval uated retrospectively by a visual inspection scoring method (A = no signifi cant uptake to D = nodular uptake superior to normal thyroid tissue). Plana r images were taken using a small field thyroid gamma camera. There were 52 patients with pT1 carcinoma (2 x follicular and 50 x papillar y). The mean tumor size was 0.56 +/- 0.26 cm. The scintigraphic results wer e A and B in 5.7 % (n = 6), C in 73 % (n = 38), D in 15.6 % (n = 8). Out of 40 patients with pT2 carcinoma, 34 had a papillary, 6 a follicular h istology. Mean tumor size was 1.66 +/- 0.49 cm. The scintiscan was A in 12. 5 % (n = 5), B in 32.5 % (n = 13), C in 42.5 % (n = 17) and D in 12.5 % (n = 5), There were 11 patients with pT3 carcinoma (4 x papillary, 7 x follicular). The mean tumor size was 3.96 +/- 0.88 cm in diameter. Scintiscan was A in 7 2.7 % (n = 8), C in 27.3 % (n = 3). Among 48 patients with pT4 carcinoma (2 x follicular, 1 x nondifferentiated , 45 x papillary), scan was A in 41.6 % (n = 20), B in 14.5 % (n = 7), C in 33.3 % (n = 16) and D in 10.4 % (n = 5). Mean tumor size was 2.16 +/- 1.45 cm (7 carcinomas II cm, 23 x 1-2 cm, the remaining >2 cm). Tumor size plays an important role in routinely used planar scintigraphy, N odules greater than 2 cm in diameter tend to appear cold but microcarcinoma s (less than or equal to 1 cm) are often indifferent on scan. Therefore, pl anar Tc-99m-pertechnetate scintigraphy is of little value in evaluating sma ll thyroid nodules. In order to diagnose small thyroid nodules, ultrasonogr aphy and ultrasonographically guided FNAB should be recommended as the init ial diagnostic steps in clinical routine.