Plexiform Schwannoma of the Middle Finger: A Rare Benign Mesenchymal Tumor Presenting as a Chronic Digital Swelling

Plexiform schwannoma (PS) is a rare, benign peripheral nerve sheath tumor characterized by a multinodular growth pattern. While common in superficial locations, such as the dermis and subcutis, its manifestation in the fingers is uncommon and can pose diagnostic challenges. We report the case of a 38-year-old female with a 10-year history of a slow-growing, mildly painful swelling over the proximal phalanx of the right middle finger. Clinical examination suggested a benign soft tissue tumor. The lesion was surgically excised under local anesthesia. Histopathology revealed a predominantly dermal-based tumor, which was unencapsulated and composed of spindle cells with hypocellular and hypercellular areas, consistent with a benign nerve sheath tumor. Immunohistochemistry showed diffuse, strong S-100 positivity, confirming the diagnosis of PS. The postoperative course was uneventful, with no recurrence at the one-year follow-up. This case highlights the importance of including PS in the differential diagnosis of soft tissue tumors of the hand to prevent misdiagnosis and ensure optimal surgical outcomes.