Rectal malignant peripheral nerve sheath tumor with extremely high Ki-67 index (80%) and concomitant meningioma...

Malignant peripheral nerve sheath tumor (MPNST) is an extremely rare and highly aggressive sarcoma with a generally poor prognosis. We report a case of a 68-year-old female with a 10-year history of meningioma resection (sporadic MPNST, no NF1 family history or clinical manifestations) who presented with anal pain without typical rectal cancer symptoms. Pelvic MRI showed a lesion in the lower rectum, presenting a "target sign" on T2WI and high signal on DWI. Postoperative pathological and immunohistochemical findings confirmed MPNST (S-100 (+), SOX-10 (+), H3K27me3 (partial loss), Ki-67 (80%)). The patient underwent laparoscopic abdominoperineal resection (APR) following the total mesorectal excision (TME) principle, achieving R0 resection. The patient recovered uneventfully without perioperative complications, and long-term surveillance was recommended. This case highlights the diagnostic challenges of sporadic rectal MPNST with non-specific symptoms and extremely high proliferative activity, and provides evidence for the feasibility of laparoscopic APR in low rectal MPNST. It also underscores the need for individualized adjuvant therapy and long-term surveillance in high-risk cases.