Recently characterized molecular events in uncommon gynaecological neoplasms and their clinical importance

The introduction of new sequencing technologies has resulted in the discovery of commonly mutated genes in uncommon cancers, including non‐epithelial ovarian neoplasms and other rare gynaecological tumours, such as cervical embryonal rhabdomyosarcoma. In some of these neoplasms, mutations in certain genes are both frequent and specific enough for the genomic mutations and sometimes their associated protein loss or overexpression to be used as an aid to diagnosis. In this review, we contrast previous gene identification methods with newer ones, and discuss how the new sequencing technologies (collectively referred to as ‘next‐generation sequencing’) have permitted the identification of specific molecular events that characterize several rare gynaecological neoplasms. We highlight the value of using sequencing to complement traditional pathological methods when diagnosing certain tumours, and provide practical advice to pathologists dealing with these neoplasms. We focus on adult granulosa cell tumours (somatic monoallelic mutations in FOXL 2 ), Sertoli–Leydig cell tumours, gynaecological embryonal rhabdomyosarcomas (germline and somatic mutations in DICER 1 ), and small‐cell carcinoma of the ovary, hypercalcaemic type (biallelic mutations in SMARCA 4 ). The new genetic findings provided by next‐generation sequencing in these uncommon neoplasms have brought these disorders back into focus, and point the way towards new diagnostic, preventive and therapeutic avenues.