Table 1.

Histopathological features frequently encountered in MMRd/MSI endometrial carcinoma.

Histopathological Features of MMRd/MSI Endometrial Carcinoma
Lower uterine segment (LUS) origin
Endometrioid differentiation
Severe nuclear atypia with undifferentiated component
High mitotic index
High tumor-infiltrating lymphocytes (TILs) and/or peri-tumoral lymphocytes (≥40 TIL/10HPFs, with more CD8+, CD45RO+ and PD1+ T cells at the invasive tumoral margin)
High morphological heterogeneity
Substantial lympho-vascular space invasion (LVSI)
Deeper myometrial invasion
Synchronous ovarian cancer (clear cell or endometrioid variants)