Inflammatory pseudotumor of nerve mimicking a benign peripheral nerve sheath tumor—a rare presentation of an uncommon entity

Abstract Background Inflammatory pseudotumor (IPT) in peripheral nerve is a rare presentation of a relatively uncommon entity, characterized by polymorphous inflammatory infiltrates and fibrosis within the lesion, and is rarely diagnosed on imaging alone. Case presentation A twenty-two-year-old male complains of insidious onset and gradually progressive swelling along the medial side of the right ankle for the last 10 years associated with dull aching pain. Ultrasonography (USG) revealed a large, heterogeneous echotexture hypoechoic fusiform lesion with mild internal and peripheral vascularity in close relation with the lateral plantar nerve. Magnetic resonance imaging (MRI) revealed a target appearance lesion closely abutting and displacing the inferior most part of the tibial nerve and lateral plantar nerves. Associated extensive subcutaneous tissue edema and panniculitis formation was also seen. USG-guided percutaneous biopsy under local anesthesia and proximal nerve block revealed IPT of neural origin with S-100 positivity. Conclusions Multidisciplinary clinico-patho-radiological collaboration plays a crucial role in the management of rare and complex lesions such as IPT of nerve, preventing misdiagnosis and improving patient outcome.