RESUMO
BACKGROUND: Reactive lymphoid follicular hyperplasia is a benign proliferation of lymphoid follicles, which can develop wherever lymphoid tissue is present. We present the unique case of an RLFH that involved the radial nerve and presented as a peripheral nerve tumor. CASE DESCRIPTION: A 62-year-old woman came to our attention because of the evidence of a mass in her right arm, associated with numbness in the lateral aspect of her right arm and forearm. Magnetic resonance findings revealed a contrast-enhancing, spindle-shaped tumor, suggestive of a schwannoma or neurofibroma, along the course of the radial nerve. The intraoperative appearance was that of an infiltrating tissue around a lateral branch of the nerve, which could be resected en bloc. Pathologic examination documented hyperplastic lymphoid tissue surrounding the nerve, and immunostaining confirmed the diagnosis of benign reactive follicular hyperplasia. Systemic infections and autoimmune disorders were excluded by screening examinations. The patient remains free of recurrence 24 months postoperatively. CONCLUSION: To our knowledge this is the first description of RLFH affecting a peripheral nerve and mimicking a neoplasm. This rare and benign condition should be considered in the differential diagnosis of peripheral nerve tumors.