Thyroid intrafollicular neoplasia (TIN) as a precursor of papillary microcarcinoma.

BACKGROUND

The aim of this study was to identify a spectrum of morphological changes from benign reactive follicles to suspected thyroid intrafollicular neoplasia (TIN) and papillary microcarcinoma observed in different pathological processes of the thyroid gland.

CASE SERIES: In a retrospective study on a total of 105 cases, occult or incidental thyroid papillary microcarcinoma was found in association with multinodular goiter (52%), chronic thyroiditis (19%), follicular adenoma (19%), parathyroid neoplasia (5%), and no evident thyroid pathology (5%).

RESULTS

Atypical follicles are described in various pathological conditions correlating with lymphoid inflammatory infiltration, stromal sclerosis, and hyperplastic or neoplastic follicular nodules. The histological pattern of papillary carcinoma is compared with morphological changes ranging from atrophic and/or reactive thyroid follicles, potential intrafollicular thyroid neoplasia (TIN) and papillary microcarcinoma.

CONCLUSIONS

The atypical features of follicular epithelial areas make up a wide spectrum that starts with the dispersion of nuclear chromatin. Low- and high-grade TIN may represent a cytological marker of dysplastic lesions and precursors of thyroid papillary carcinoma when it is still in an early intrafollicular or pre-invasive stage in various pathological processes of the thyroid.