Expansion
Chromatin pattern, nucleoli and shape indicate activity and malignancy
Expansion
Normal variation
- Euchromatin: pale, dispersed, transcriptionally active
- Heterochromatin: dark, condensed, inactive. A small dense nucleus indicates a quiescent cell such as a lymphocyte
- Prominent nucleolus: active ribosome production, seen in plasma cells and in malignancy
- Barr body: the inactivated X chromosome, a peripheral chromatin clump in female cells
Features suggesting malignancy
- Increased nuclear to cytoplasmic ratio
- Pleomorphism: variation in size and shape
- Hyperchromasia: dark staining from increased DNA
- Irregular nuclear membrane, coarse clumped chromatin
- Prominent or multiple nucleoli
- Abnormal mitotic figures, and increased mitotic count
- Loss of polarity and architectural disorganisation
Characteristic nuclear appearances worth recognising: Reed-Sternberg owl eye nuclei in Hodgkin lymphoma; Orphan Annie nuclei with clearing and nuclear grooves in papillary thyroid carcinoma; salt and pepper chromatin in neuroendocrine tumours; and hypersegmented neutrophil nuclei in megaloblastic anaemia.