Resident Program - Case of the Month

Clinical History

A 72-year-old female had history of a thyroid mass discovered by her PCP on routine exam. Thyroid ultrasound performed at outside hospital showed bilateral thyroid nodules: a right lobe heterogeneous predominantly hypoechoic solid 3.2 x 2.3 x 2.0 cm nodule (considered suspicious), and a left lobe upper pole 2.5 x 1.9 x 1.6 cm nodule (considered mildly suspicious). Then outside follow-up ultrasound-guided FNA on the right demonstrated papillary thyroid carcinoma (slides not reviewed by UC Davis Pathology), and on the left demonstrated no evidence of malignancy. Then she presented to UC Davis Health for total thyroidectomy.

Gross and Microscopic Description

Grossly, the right thyroid lobe has a pink-tan, well-circumscribed, focally calcified 2.8 x 2.2 x 1.5 cm nodule, which extensively abuts the thyroid capsule. Microscopically, the nodule has a thin capsule and predominantly trabecular architecture with focal follicle formation, and prominent hyalinized stroma containing amyloid-like amorphous material (highlighted by bright PAS staining, Figure 5). Cytologically, the tumor cells are polygonal to tall with abundant eosinophilic cytoplasm, irregular nuclear contours, numerous nuclear grooves and intranuclear cytoplasmic pseudoinclusions, and scattered refractile cytoplasmic granular inclusions. No transcapsular or lymphovascular invasion is identified, and the tumor is completely confined to the thyroid gland.

The following immunohistochemistry (IHC) stains were performed:

Figure 1 - H&E		Figure 2 - H&E
Figure 3 - H&E		Figure 4 - H&E
Figure 5 - PAS		Figure 6 - H&E
Figure 7 - H&E		Figure 8 - TTF 1 (IHC)

The above features are compatible with which of the following?

Choose one answer and submit.