Serial transverse sections through right and left lobes and sagittal sections through isthmus (orientation as marked)
- the gland is enlarged
- the normal tan, fleshy appearance of thyroid parenchyma (residual parenchyma seen in the left lobe) is now seen as pale and homogeneous (R>L)
- sonographically-noted isthmic lesion is identified
- no other suspicious macroscopic lesions
- low power: extensive replacement of thyroid parenchyma by diffuse reactive lymphoid infiltrate including activated follicles with germinal centres. There is a zone of residual identifiable parenchyma in the top right corner.
- high power: sheets of uniform, small, regular lymphocytes surrounding scattered residual follicles (bottom right).
- there is gross distortion and replacement of normal thyroid microscopic architecture
- the engulfed follicular epithelium often shows associated cytological changes including nuclear activation and cytoplasmic oncocytic/Hurtle cell change
The isthmus cystic lesion was benign on histological examination