Paper II
Question
Morphological features of papillary carcinoma thyroid
Answer
Papillary carcinoma is the most common type of thyroid carcinoma, with an excellent overall prognosis.
Gross features
- May be well-circumscribed or infiltrative; can be solitary or multifocal; grey-white, firm, may show areas of calcification/fibrosis
Microscopic (nuclear) features (the diagnostic hallmarks — diagnosis is based on nuclear features, not architecture)
- Optically clear/empty nuclei (“Orphan Annie eye” nuclei) — due to margination of chromatin
- Nuclear grooves — longitudinal folds in the nuclear membrane
- Intranuclear cytoplasmic pseudoinclusions — invaginations of cytoplasm into the nucleus
- Overlapping nuclei
Architectural features
- Papillary architecture (finger-like projections with a fibrovascular core) — though a follicular variant also exists, retaining the diagnostic nuclear features without true papillae
- Psammoma bodies — concentrically laminated, calcified structures, often found within the papillary cores (highly characteristic, though not universally present)
Behaviour
- Tends to spread via lymphatics to regional (cervical) lymph nodes rather than haematogenously
- Excellent prognosis overall, particularly in younger patients