anaplasia
Pronunciation: an-uh-PLAY-zhuh
A histological feature of tumour cells showing marked nuclear enlargement, hyperchromasia, and atypical mitotic figures, used specifically in Wilms tumour grading to define unfavourable histology.
Full Definition
In pediatric pathology, anaplasia specifically refers to a defined histological criterion in Wilms tumour: nuclei at least three times the diameter of adjacent cells, with hyperchromasia and multipolar mitotic figures. It is classified as focal (confined to a discrete region without nuclear atypia elsewhere) or diffuse (present in multiple sections or extrarenal sites), with diffuse anaplasia carrying the worst prognosis. Editors must be careful not to use 'anaplasia' as a general synonym for 'poorly differentiated', particularly in contexts outside Wilms tumour, as the term carries specific diagnostic thresholds. In reports concerning other pediatric tumours, the preferred term may be 'undifferentiated' or 'high-grade'.
Usage
Usage note: Always specify 'focal' or 'diffuse' anaplasia in Wilms tumour reports; the unmodified term alone is insufficient for staging purposes.
In Context
- "Focal anaplasia was identified in a single intrarenal site, supporting classification as favourable-histology Wilms tumour under current COG criteria." — Surgical pathology report
- "The author used 'anaplastic' and 'undifferentiated' interchangeably; the copy-editor flagged this as imprecise in the context of Wilms tumour grading." — Journal manuscript edit