Aspiration cytology of pediatric solitary papillary hyperplastic thyroid nodule

Solitary papillary hyperplastic thyroid nodules (SPHTNs) are frequently encountered in children and teenagers. Although the histologic features are well described, to the best of our knowledge, cytologic findings have not been reported.

To review the cytologic features of histologically proven SPHTNs and to identify the potential diagnostic pitfalls in cytologic diagnosis.

Fine-needle aspiration cytology of 3 histologically proven SPHTNs was reviewed.

Two girls and 1 boy (ages 11, 12, and 15 years) were affected. The cytologic diagnosis in all 3 cases was suspicious for papillary thyroid carcinoma (PTC). The spectrum of cytologic findings included broad flat sheets and 3-dimensional clusters with fire flares. There was mild to moderate nuclear pleomorphism and nuclear atypia. Short nonbranching papillae with transgressing vessels shown to represent hyperplastic papillae on histologic sections were identified in all cases. The background contained giant cells, histiocytes, and watery and inspissated colloid. Although nuclear grooves were identified in occasional cells, intranuclear inclusions were absent. A cell block section (1 case) and histologic sections of SPHTNs (2 cases) were immunohistochemically negative for cytokeratin 19.

Fine-needle aspiration of SPHTNs may be difficult to interpret accurately and can result in false-positive diagnosis of PTC. Although it shares several cytologic features with PTC, the presence of fire flares and short nonbranching papillae, as well as lack of intranuclear inclusions and watery and inspissated colloid in SPHTN appear to be useful features that are helpful in distinguishing SPHTN from PTC. Negative immunohistochemical staining for cytokeratin 19 is useful in excluding a diagnosis of PTC.