Rare non-epithelial ovarian neoplasms: Pathology, genetics and treatment.

Rare non-epithelial ovarian neoplasms have posed management challenges for many years. Their rarity means that most specialist practitioners will see one such case every several years, and most generalists may never see a case. The first step in management is to establish the correct diagnosis and this may necessitate specialist pathology review. Here, we review recent developments in the pathology, genetics and treatment of small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) and sex cord-stromal tumours. Pathologically, these tumours often display morphological overlap with other neoplasms; for example, SCCOHT overlaps with many other "small round blue cell" tumours. Specific immunohistochemical stains, while useful, may not always be definitive. The discovery of somatic mutations in FOXL2 (adult granulosa cell tumours) and germline and somatic mutations in DICER1 (Sertoli-Leydig cell tumours) and SMARCA4 (SCCOHT) has demonstrated the value of molecular investigation as an adjunct to traditional histopathological approaches. In addition, the presence of germline mutations in a significant proportion of some of these neoplasms points to the need for genetic counselling and testing, offering the prospect of prevention and early diagnosis. Treatment of these rare tumours, as a group, should be on the basis of sound oncological principles, given that level 1 evidence will almost always be lacking. The rationale for experimental therapies must be clearly established. In view of the complex issues involved in the management of these conditions, expert opinion in pathology, genetics and treatment may be essential to offer the patient and her family the best chance of a good outcome.