Abstract
Fine-needle aspiration (FNA) is not necessary in adults with nodules ≤ 1 cm without
apparent extrathyroidal extension (ETE) or lymph node (LN) involvement on ultrasonography
(US). In the absence of FNA and serum calcitonin (Ctn) measurement, medullary thyroid
microcarcinomas (microMTC) are not diagnosed. The aim of this prospective study was
to evaluate Ctn levels in adults with a low clinical risk of MTC and nodules ≤ 1 cm
without ETE or LN involvement on US. A total of 506 consecutively seen adults who
had nodules with two or more suspicious features were included. Patients with elevated
basal Ctn underwent a calcium stimulation test and FNA. Basal Ctn was normal in 490
patients (96.8%). In the 16 patients with elevated basal Ctn, FNA revealed MTC in
only one patient and MTC was not suspected in the 15 patients with elevated basal
Ctn. Three patients with stimulated Ctn<100 pg/ml and benign cytology were not submitted
to surgery. MTC was excluded by histology in three patients with stimulated Ctn<100 pg/ml
and indeterminate or suspicious cytology and in eight patients with stimulated Ctn>100 pg/ml.
One patient with stimulated Ctn>100 pg/ml had MTC. Ctn was undetectable 6 months after
surgery in two patients with MTC. Although uncommon, even subjects without a suspicious
history and with nodules ≤ 1 cm without ETE or LN involvement on US, but with suspicious
findings, can have microMTC. The measurement of Ctn permits the diagnosis of these
cases.
Key words
thyroid nodule - microcarcinoma - medullary thyroid carcinoma - serum calcitonin -
fine-needle aspiration
