Transperineal excision of malignant peripheral nerve sheath tumors of the ischiorectal fossa: Case report of a rare tumor in a frequently forgotten anatomical region

•Malignant peripheral nerve sheath tumors are very rare: this is the first description of localization in ischiorectal fossa.•The histological diagnosis of malignant peripheral nerve sheath tumors can be a surprise.•Malignant peripheral nerve sheath tumor of the ischiorectal fossa can be successfully excised with transperineal approach.•Radiotherapy should be a completion of the therapy, even if the literature lacks studies in this sense.