Papillary thyroid carcinoma variants

Abstract

Papillary thyroid carcinomas are the most common thyroid cancers and constitute more than 70% of thyroid malignancies. The most common etiologic factor is radiation, but genetic susceptibility and other factors also contribute to the development of papillary thyroid carcinoma. The most common variants include conventional, follicular variant and tall cell variant. However, many other uncommon variants have been described including oncocytic, columnar cell, diffuse sclerosing and solid forms. Immunohistochemical staining with TTF-1 and thyroglobulin is very useful in confirming the diagnosis of papillary thyroid carcinoma especially in metastatic sites. Markers such as HBME-1 and CITED1 can assist in separating some difficult cases of follicular variants of papillary thyroid carcinomas from follicular adenomas. Molecular studies have shown that the BRAF V600E mutation is found mainly in papillary and anaplastic thyroid carcinomas. Other molecular markers such as HMGA2 and insulin-like growth factor II mRNA binding protein 3 have been used recently as molecular tests to separate papillary thyroid carcinoma and its variants from follicular adenomas and other benign thyroid nodules.

Figures

Fig. 1

Conventional papillary thyroid carcinoma and papillary thyroid carcinoma variants. a Conventional papillary thyroid carcinoma. The carcinoma has papillae with fibrovascular cores and enlarged nuclei with nuclear clearing. b Follicular variant of papillary thyroid carcinoma. The follicles are made up of cells with enlarged nuclei with cytologic features of papillary carcinoma. The colloid is darker and shows scalloping. c Tall cell variant of papillary thyroid carcinoma. The cells are 2–3 times as tall as they are wide and show cytologic features of papillary thyroid carcinoma. d Columnar cell variant of papillary thyroid carcinoma. The pseudostratified cells have enlarged nuclei which are overlapping

Fig. 2

Variants of papillary thyroid carcinoma. a Oncocytic variant with large cells showing abundant eosinophilic cytoplasm and nuclear features of papillary thyroid carcinoma. b Solid variant with sheets of tumor cells with abundant cytoplasm and nuclear features of papillary thyroid carcinoma including cytoplasmic invagination into nuclei. c Diffuse sclerosing variant showing abundant psammoma bodies, and squamoid changes in the tumor cells. A prominent lymphocytic infiltrate is present in the background. d Papillary thyroid carcinoma with prominent hobnail features. The tumor consists of hobnail cells with loss of polarity and high grade cytologic features including prominent nucleoli and increased mitotic activity