Epithelioid Malignant Peripheral Nerve Sheath Tumor (Epithelioid-MPNST) Presenting as Bleeding Rectal Polyp: A Case Report with Systematic Literature Review.

BACKGROUND Malignant peripheral nerve sheath tumor (MPNST) with pure epithelioid histology MPNST (epithelioid-MPNST) is a distinctly rare variant of MPNST described by World Health Organization. Occurrence of MPNST in the tubular gut is extremely rare with nearly 20 cases reported in the last 40 years. CASE REPORT In this case report, we described 2 such cases of epithelioid-MPNST occurring in a 65-year male and 47-year-old female, who both presented with bleeding rectal polyps. We also report on our comprehensive systematic literature review. CONCLUSIONS To the best of our knowledge, these are possibly the first two cases of pure epithelioid-MPNST at an unusual site. This needs to be differentiated from lesions more commonly encountered at the related anatomical site, such as malignant melanoma, poorly differentiated carcinoma, lymphoma, or even a gastrointestinal stromal tumor, by appropriate panel of antibodies.