Solid/Trabecular Variant of Papillary Thyroid Carcinoma

Abstract

A 68-year-old Japanese woman visited our hospital with a complaint of neck mass increasing in size for the last 10 months. Thyroid function tests were within normal limits, and all the thyroglobulin antibodies were negative. Ultrasonographic examination found a mass measuring 19 × 14 × 10 mm occupying the left mid-lobe of the thyroid. Color Doppler ultrasound revealed a hypervascular flow. Ultrasonographically, the mass was interpreted as a malignant lesion. Fine needle aspiration biopsy was performed to determine the cytological diagnosis. Cytologically, papillary thyroid carcinoma (PTC) was highly suspected, but the possibility of poorly differentiated thyroid carcinoma was also postulated. Histological examination of the mass revealed proliferation of tumor cells forming solid nests occupying approximately more than 90% of the entire tumor, whereas the remainder consists of the papillary architecture. No necrosis or hemorrhage was present. The solid nest consists of tumor cells preserving features of PTC including pseudo-inclusions. Severe nuclear atypia or mitotic figures were rarely identified. Based on these findings, the diagnosis of solid/trabecular variant of papillary thyroid carcinoma was rendered.