Endocrine Abstracts (2006) 11 P890

Immunohistochemical staining for thyroid peroxidase (TPO) of tru-cut biopsies from scintigraphically cold thyroid nodules

UY Yousaf, LC Christensen, AKR Rasmussen, FJ Jensen, EH Hilmer, CM Mollerup, JK Kirkegaard, IL Lausen & UFR Feldt-Rasmussen

Rigshospitalet, Department of Endocrinology, 2131, Copenhagen, Denmark.

Background: Scintigrafically cold nodules are hypofunctioning areas in the thyroid gland. These nodules are common and as the risk of malignancy is low, surgery is only necessary in very few cases. Fine Needle Aspiration Cytology (FNAC) is the standard method for detecting malignant tumours. However, FNAC is a difficult diagnostic procedure which often gives insufficient working material.

Materials and methods: A prospective study was designed to calculate the diagnostic sensitivity and specificity of tru-cut based diagnosis and TPO immunostaining for patients with a post-operative diagnosis. All patients with a scintigrafically, solitary cold thyroid nodule or a dominant cold nodule in a multinodular thyroid gland where included. The study was conducted during a 5-year period. All patients underwent a tru-cut biopsy. The patients were subsequently allocated to either thyroidectomy or follow-up. The tru-cut based diagnosis was evaluated by comparison with the post-operative diagnosis. The diagnostic sensitivity and the diagnostic specificity were calculated.

Results: A total of 427 patients with a cold thyroid nodule where included. The TPO staining of tru-cut biopsy was compared with tru-cut based diagnosis for all patients. 141 patients underwent thyroidectomy and 286 patients were followed-up during the 5-year study period. For the 141 operated patients the diagnostic concordance between tru-cut based dignosis and post-operative diagnosis was 100% for Papillary- (17), Follicular- (1), Medullary- (1) and Undifferentiated- (3) Carcinomas. Only Adenomas and Minimally Invasive Follicular Carcinomas were not reliably diagnosed as either benign or malignant by tru-cut biopsy. The diagnostic sensitivity and specificity were 89% and 99%, respectively.

Conclusions: Histology of the nodule from tru-cut biopsy was easily determined. TPO-staining of tru-cut bioptic material had a diagnostic sensitivity of 89%, what made the difference was the Minimal Invasive Follicular Carcinomas (3). The diagnostic specificity was 99%, the only inconsistency was for Adenoma (1).

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