Plexiform schwannoma.

We present a case of plexiform schwannoma, a rare benign peripheral nerve sheath tumour characterized by a multinodular and plexiform growth pattern, that had slowly grown for 40 years on the trunk of a 64-year-old woman. Preoperative biopsy findings, such as a high cellularity and the extent of nuclear atypia of the tumour, led us to suspect a malignant peripheral nerve sheath tumour; but ultimately a benign plexiform schwannoma was diagnosed based on an immunohistochemical review of the excised tumour using various markers including S-100 and Ki67 (MIB1).