Contributed by Rebecca Leeman-Neill, MD, PhD, Somak Roy, MD, and Yuri Nikiforov, MD, PhD
The patient is a 63 year old woman with elevated calcium who, on work-up for hyperparathyroidism, was found to have a single nodule within the superior pole of the left lobe of her thyroid, measuring 0.5 cm, as well as three hypoechoic nodules of the right lobe, measuring up to 2.0 cm. The patient underwent surgical parathyroid exploration and total thyroidectomy after fine needle aspiration of the dominant right lobe nodule demonstrated a "follicular neoplasm or lesion." However, the remainder of this case will focus on a smaller right lobe nodule that was not biopsied.
Grossly, a 0.5 x 0.5 x 0.5 cm right superior pole nodule was found to be well-circumscribed, thinly encapsulated, solid, tan and soft (Figure 1, Gross appearance of thyroid nodule ).
Histologic sections demonstrated a well-circumscribed, encapsulated lesion with cells showing enlarged nuclei, with an open chromatin pattern, prominent nucleoli, some with nuclear grooves and some nuclear overlap (Figures 2, H&E, low power and 3, H&E, high power). Immunohistochemical staining demonstrated positivity for HBME-1 (Figures 4, HBME-1, low power and 5, HBME-1, high power).