Case: 50 year old female with an asymptomatic neck (thyroid) mass.

MORE IMAGES + DESCRIPTION:

Well circumscribed nodule

Large, polygonal/elongated cells; eosinophilic finely granular cytoplasm

Round nuclei with vesicular chromatin, frequent nuclear grooves, inclusions, and membrane irregularities

DIAGNOSIS? Click Here: Go into "case info" of this WSI

TAKE-AWAYS OF THIS DIAGNOSIS

MORPHOLOGY

Well - circumscribed

● Solid, well-circumscribed nodule

● Wide trabeculae and nests separated into bundles by stroma

● Large, polygonal/elongated cells; eosinophilic finely granular cytoplasm; occasional perinuclear yellow bodies

● Round nuclei with vesicular chromatin, frequent nuclear grooves, inclusions, and membrane irregularities (can be mistaken for PTC on FNA)

● Cells may be enveloped by hyalinized PAS-d (+) basement membrane material

● Absence of capsular, vascular, and parenchymal invasion

Intranuclear inclusions

OTHER HIGH YIELD POINTS

● Rare, follicular derived neoplasm

● Encapsulated and solid and less than 2.5 cm grossly

● IHC: (+) TTF-1, thyroglobulin; (-) calcitonin; unique membranes staining with MIB1 (Ki67 clone)

● Excellent prognosis. There is a rare malignant counterpart (hyalinizing trabecular carcinoma).

HYALINIZING TRABECULAR TUMOR SLIDE - CLICK HERE