PNET/Ewing's sarcoma of the rectum: a case report and review of the literature.

A 34-year-old female presented with anorectal pain and rectal bleeding due to an extensive rectal tumour. A trephine loop ileostomy was fashioned and biopsies were initially reported to show a poorly differentiated cloacogenic carcinoma. CT revealed numerous liver metastases. A histological review and immunohistochemical studies subsequently favoured a primitive neuroectodermal tumour (PNET). Stem-cell supported chemoradiotherapy resulted in complete resolution of her primary tumour and liver metastases. Serial CT scanning and endoscopy revealed no recurrence after 7 years of follow-up, when she presented with a malignant anal fissure. Imaging and subsequently abdominoperineal resection revealed no evidence of metastases from either the anal cancer or the PNET tumour. Histopathology showed a T1N0R0 basaloid squamous carcinoma originating from grade III squamous intraepithelial neoplasia with no obvious wart viral infection.