Sclerosing stromal tumour: a clinicopathological study of 100 cases of a distinctive benign ovarian stromal tumour typically occurring in the young

Aims Since the sclerosing stromal tumour (SST) of the ovary was first described in 1973, few studies have expanded upon its histological features or overlap with other tumours. We thus investigate these aspects based on our experience with 100 cases. Methods and results The patients, 14 of whom were pregnant, ranged from 12 to 63 years (median = 26 years). Ten patients had hormonal manifestations (seven oestrogenic, three androgenic). Bilateral ovarian involvement was present in two cases. Size ranged from 1 to 23 cm (mean = 8.4 cm). Most tumours were solid and white with focal yellow areas; oedema with cystic degeneration (seen in 25 cases) resulted in eight being predominantly cystic. On microscopic examination, alternating cellular and paucicellular areas (pseudolobulation) were prominent in 94 cases but seen to a limited degree in the remaining neoplasms. Admixed spindled and luteinized cells were present in all tumours, but 13 demonstrated mainly spindled cells and 19 demonstrated mainly lutein cells; 14 of the latter were from pregnant patients. The stroma was typically oedematous or collagenous, but in 14 cases was prominently hyalinised and, in four, myxoid. Prominent vascularity was present in most cases. The mitotic rate ranged from 0 to 8/10 high-power fields (HPF), but most demonstrated <1/10 HPF. Conclusions The differential diagnosis of SST is broad, including fibromas, thecomas, solitary fibrous tumours, pregnancy luteomas, myxomas, other ovarian sex cord-stromal tumours with sclerosis and, rarely, Krukenberg tumours. Strict adherence to the requirement of pseudolobulation, prominent (usually ectatic) vessels, and lutein cells and fibroblasts admixed in a jumbled manner, will distinguish the neoplasm from others in the differential.