By testing suspicious thyroid nodules for the presence of galectin-3, a substantial number of unnecessary surgical procedures could be eliminated, according to an article released on May 19, 2008 in The Lancet Oncology.

Screening potentially cancerous thyroid nodules is presently an inexact science. In fact, approximately 85% of all nodules removed surgically are actually benign. The current preliminary method of screening lesions for malignancy involves morphological examination of the cells inside that have been extracted by fine-needle aspiration. However, based on this kind of cytology, it is very difficult to distinguish between cancerous and non-cancerous thyroid cells. According to the authors: “The high prevalence of thyroid nodules in the adult population (19-67% of randomly selected individuals) and the low prevalence of thyroid cancers, makes the diagnosis of thyroid cancer difficult.”

Galectin-3, which is a lectin molecule that binds specific sugars, is not normally found in the cytoplasm of healthy thyroid cells. If it is abnormally present, it can block cell death, leading to the development of cancer.

To investigate the use of galectin-3 measurement as a method of differentiating between benign and malignant cells and thus reduce the number of unnecessary procedures, Armando Bartolazzi from St Andrea Hospital, Rome, Italy, and colleagues performed a national study in 465 subjects who had thyroid nodules larger than 1cm in diameter for which malignancy could not be determined. Subjects were enrolled between Jun 1, 2003 and August 30, 2006, were mostly women, ranged in age from 21 to 76 years, and had an average age of 50.

The nodules were removed and analyzed with histological testing after removal to determine whether they were cancerous or not. These results were compared to the results of galectin-3 tests. In 71% (331/465) of the nodules, galectin-3 was not expressed. Of these galectin-3 negative nodules, 85% (280/331) of them were, as predicted, benign, but 9% (29/331) were cancerous and thus indicated potential false negatives. Of these, 28% (8/29) showed different galectin-3 expression when tested post-operatively, suggesting that the false result could have been caused by technical problems in the test. The authors say that this sort of error could be improved on with more specific technical training.

Finally, the sensitivity of this test was 78% (95% confidence interval: 74-82), and it had a specificity of 93% (90-95). The positive predictive value was 82% (79-86) and the negative predictive value was 91% (88-93).

In conclusion, the authors point out the promise this new testing method could have in combination with the currently used methods of diagnosing nodules. “The galectin-3 method proposed here does not replace conventional FNA-cytology, but represents a complementary diagnostic method for those follicular nodules that remain indeterminate. The correct approach for this preoperative characterisation of thyroid nodules always needs careful multidisciplinary assessment of each patient, according to published guidelines.”

Galectin-3-expression analysis in the surgical selection of follicular thyroid nodules with indeterminate fine-needle aspiration cytology: a prospective multicentre study
Armando Bartolazzi, Fabio Orlandi, Enrico Saggiorato, Marco Volante, Federico Arecco, Ruth Rossetto, Nicola Palestini, Ezio Ghigo, Mauro Papotti, Gianni Bussolati, Marco Paolo Martegani, Federico Pantellini, Angelo Carpi, Maria Rosaria Giovagnoli, Salvatore Monti, Vincenzo Toscano, Salvatore Sciacchitano, Gian Maria Pennelli, Caterina Mian, Maria Rosa Pelizzo, Massimo Rugge, Giancarlo Troncone, Lucio Palombini, Gennaro Chiappetta, Gerardo Botti, Aldo Vecchione, Rino Bellocco, for the Italian Thyroid Cancer Study Group (ITCSG)
Lancet Oncology, May 19, 2008
DOI:10.1016/S1470-2045(08)70132-3
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Written by Anna Sophia McKenney