Testing potentially cancerous thyroid nodules for the presence of galectin-3 could substantially decrease the number of unnecessary surgical procedures, say authors of a paper published early Online in The Lancet Oncology.
Testing thyroid nodules for cancer is an inexact science—about 85% of nodules removed by surgery turn out to be benign. The standard method of assessing whether or not a lesion is malignant is to examine cells extracted by fine-needle aspiration. However, distinguishing between cancerous and non-cancerous thyroid cells on a morphological basis alone can be difficult. "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”, say the authors. Galectin-3 is a lectin molecule that is not normally present in the cytoplasm of thyroid cells; when it is abnormally present, the protein can block cell death, triggering the development of cancer.
Armando Bartolazzi from St Andrea Hospital, Rome, Italy, and colleagues undertook a national study to assess whether testing for galectin-3 could differentiate between benign and malignant cells and therefore prevent unnecessary surgical procedures. They tested galectin-3 expression in 465 people scheduled for surgery to remove thyroid nodules that could not be determined by cytology as benign or malignant. Patients were enrolled in the study between June 1, 2003, and August 30, 2006; most were women (76%) and the mean age was 50 years (range 21 to 76 years). Individuals with thyroid nodules smaller than 1 cm in diameter were not enrolled.
After the nodules were removed, the final histological results that determined whether or not they had been cancerous were compared with the findings from galectin-3 testing.
Galectin-3 was not expressed in 331 (71%) of 465 nodules. 280 (85%) of these galactin-3-negative nodules turned out to be benign, but 29 (9%) were cancerous (the remaining 6% were borderline cases). Of these 29 false-negatives, 8 had a different galectin-3 expression in post-operative testing, suggesting that there might have been some technical problems in the testing (which the authors say could be improved upon with specific technical training).
The sensitivity of the test was 78% (95% CI 74–82) and specificity was 93% (90–95). The positive predictive value was 82% (789–86) and negative predictive value 91% (88–93).
The authors conclude: "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".
Dr Armando Bartolazzi, Department of Pathology, St Andrea Hospital, Via di Grottarossa 1035, 00189 Rome, Italy. Armando.Bartolazzi@ki.se T): +39-063 377 5321
http://www.eurekalert.org/jrnls/lance/pdfs/TLOthyroidfinal.pdf
Journal
The Lancet Oncology