Chapter 1: Histopathology of gynaecological cancers
Uterine corpus tumours – Non-epithelial tumours
The majority of non-epithelial tumours affecting the uterine corpus are mesenchymal, including the very common leiomyoma, and rare uterine sarcomas (3% of uterine malignancies).
The most common uterine sarcoma is leiomyosarcoma (LMS), followed by endometrial stromal sarcoma (ESS), the latter divided into low and high-grade entities (LG-ESS, HG-ESS).
Leiomyomas are clonal, morphologically heterogeneous, and often harbour MED12 mutations, whereas leiomyomas with bizarre nuclei may be associated with fumarate hydratase (FH) deficiency (Figure 1.13).
Figure 1.13: Leiomyoma with FH deficiency
Abbreviations: FH, fumarate hydratase.
Credit: Courtesy of the authors
Uterine sarcomas: LMSs are clinically aggressive tumours, stain for muscle markers (desmin, actin, caldesmon), and may harbour mutations in TP53, ATRX and MED12.
LG-ESS express CD10 and hormone receptors, whereas HG-ESS are often negative for these markers and show overexpression of cyclin D1 or BCOR.
LG-ESS carry different fusion genes, most commonly JAZF1-SUZ12, whereas HG-ESS have YWHAE-NUTM2A/B fusion or fusions involving BCOR (Figure 1.14).
Figure 1.14: Gene fusions in ESS
Abbreviations: ESS, endometrial stromal sarcoma; HG-LSS, high-grade ESS; LG-ESS, low-grade ESS.
Credit: Micci F, et al. Cancer 2021;60:160-167
Gestational trophoblastic disease (GTD) includes tumour-like conditions, molar pregnancies (partial, complete or invasive mole) and gestational trophoblastic neoplasia (GTN) (Figure 1.15).
Figure 1.15: WHO 2020 classification of gestational trophoblastic disease (GTD)
Abbreviations: WHO, World Health Organization.
Credit: Kaur B. Best Pract Res Clin Obstet Gynaecol 2021;74:3-28
Complete mole carries a 15%–20% risk for persistent disease and a 2%–3% risk of developing choriocarcinoma, the most common and clinically aggressive GTN.
The diagnosis of molar pregnancy is based on p57 immunostaining and DNA content, the latter by genetic typing.
Revision Questions
- Which types of sarcomas are most common in the uterus?
- Which type of genetic change is characteristic of ESS?
- Which ancillary tests are used in the diagnosis of molar pregnancy?
