Plexiform neurofibroma without neurofibromatosis type 1: A case report

Plexiform neurofibromas are a less common type of tumor (occurring in 30% of cases) associated with neurofibromatosis type 1 (NF-1). These tumors develop from multiple nerves, often appearing as bulging, disfiguring masses that can involve surrounding connective tissue and skin. We describe an unusual case of a 38-year-old male who presented with a painless swelling in the left preneal region that had been present since early childhood. A physical examination did not reveal the presence of multiple neurofibromas or café-au-lait macules on the trunk and arms. Cytological examination of biopsy samples obtained through ultrasound-guided fine needle aspiration revealed a spindle cell neoplasm. Subsequent pelvic magnetic resonance imaging (MRI) confirmed the presence of a solid, enhancing mass in the left perianal region. Following the patient's request for surgical intervention, an excisional biopsy was performed, which ultimately revealed the diagnosis of plexiform neurofibroma. Plexiform neurofibromas are typically diagnosed based on clinical findings, particularly when accompanied by other characteristic features of neurofibromatosis type 1. Treatment often involves surgery to remove disfiguring masses and any cancerous tissue that may have developed. • Isolated plexiform neurofibroma occurring without any clinical features of NF-1 is extremely rare and may represent somatic mosaicism or a subclinical NF-1 variant. • Clinical, cytological, MRI, and histopathological correlation was essential for diagnosis in the absence of genetic testing, emphasizing the value of multimodal evaluation in resource-limited settings. • The patient presented with a long-standing perianal mass without café-au-lait macules, axillary freckling, Lisch nodules, or family history, underscoring the diagnostic challenge of differentiating isolated plexiform neurofibroma from NF-1. • Complete surgical excision resulted in good postoperative outcomes with no recurrence at 6-month follow-up, supporting surgery as the mainstay of management for symptomatic or enlarging lesions. • The case highlights the importance of long-term surveillance due to the small but possible risk of recurrence or malignant transformation, even in isolated plexiform neurofibromas.