A Rare Case of Perineurioma of the Posterior Interosseous Nerve: A Case Report.

The perineurioma (PN) is a benign neoplasm with perineural origin. It can be of two types, i.e., intraneural PN and extraneural PN. It is slow-growing in nature and frequently causes hypoesthesia and progressive motor weakness other than swelling. The size of the swelling ranges from small to large. The entity is difficult to distinguish from Schwannoma and other peripheral nerve sheath tumors clinically, pathologically, and radiographically (MRI). An early diagnosis is needed as the PN arises from a nerve and can be salvable if preoperative planning is well executed. Here, in this case, report, the nerve involved was the posterior interosseous nerve (main motor nerve of the finger/wrist extensors), which is a rare phenomenon of occurrence; however, early intervention and the benign nature of the tumor can be handled with a good prognosis, and recurrence is usually rare but could not be ignored as documented.