Ewing’s sarcoma / PNET of rectovaginal septum

Aim Peripheral primitive neuroectodermal tumour (PNET) in the female genital tract is uncommon. Awareness of the occurrence of PNET in the genital tract and distinguishing it from other tumours is important as this tumour is potentially more aggressive and requires different treatment. The following case describes the pathological findings of this rare tumour. Methods A case of PNET in the rectovaginal septum is presented. Results A 40-year-old female presented with acute urinary retention due to a mass in the pouch of Douglas, contiguous with the rectovaginal septum. Histological examination revealed the nature as small round cell tumour (SRCT). Tumour was positive for CD99 while negative for keratin, neuroendocrine, melanocyte and muscle differentiation markers. Diagnosis of PNET was confirmed by genomic studies. Discussion Although rare, PNET can present in the vaginal septum and therefore it is important to consider PNET as a differential diagnosis for all small round cell tumours. A combined histological, immunohistochemical and molecular genetic approach is essential for a reliable diagnostic characterisation of SRCT.