Nuclear features of papillary thyroid carcinoma: Comparison of Core needle biopsy and thyroidectomy specimens

Core needle biopsy (CNB) has been used as an alternative or a complementary method for diagnosis of thyroid nodules. However, morphological analysis of the nuclear features of papillary thyroid carcinoma (PTC) cells obtained via CNB remains unclear. Hence, we examined the differences between the PTC nuclear features in CNB and thyroidectomy specimens.

Ten PTC patients, who underwent both CNB and thyroidectomy, were selected. Microscopic photographs of three representative areas of the PTC and adjacent parenchyma were taken. Ten cells per photograph were chosen, and 1200 cells were evaluated (300 PTC and 300 follicular cells in the CNB and thyroidectomy specimens, respectively). The area, circumference, major axis, and minor axis were measured using an image analyzer. Detailed nuclear features (size and shape, membrane irregularity, chromatin characteristics) were scored using a 3-point scale.

The mean nuclear area, circumference, major axis, and minor axis of PTC cells in the CNB specimen were 1.76, 1.34, 1.34, and 1.29 times larger than those of the follicular cells (p<0.001); similar results were seen in the thyroidectomy specimens (2.04, 1.41, 1.37, and 1.37: p<0.001). Comparative analysis revealed that these parameters were significantly smaller in the CNB specimens than those in the thyroidectomy specimens (p<0.001). Nuclear grades were also lower in the former owing to poor chromatin characteristics (clearing and margination) (p<0.01).

Considering that the PTC nuclei in CNB specimens are smaller with fewer irregularities and less clear than those in thyroidectomy specimens, we need to emphasize caution when using CNB specimens for diagnosis.