Plexiform neurofibroma is a subcutaneous or dermal tumor of the peripheral nerve sheath surrounding one or more nerve fascicles. It can occur in isolation or in patients with neurofibromatosis type 1. This tumor is usually benign although a small minority can undergo a malignant transformation. Diagnosis relies on ultrasound, computed tomography, magnetic resonance imaging, and histopathological evaluation.
The name plexiform neurofibroma (PN) is derived from its appearance in the form of a network or a plexus surrounding branches of a peripheral nerve. It is typically a benign tumor and is composed of Schwann cells, perineurial components, fibroblasts, and hematopoietic cells surrounded by collagenous or myxoid stroma . Although it can occur anywhere on the body, the head and neck region are the commonest sites .
Clinically, patients present with an irregular, tortuous subcutaneous or dermal mass resembling a "bag of worms" . Other symptoms and signs depend on the mass effect of this swelling and it is essential to exclude extrinsic compression on neighboring structures or bone abnormalities. Tissue damage can lead to pain and sensorimotor deficits even in benign PN .
Although a plexiform neurofibroma is not pathognomonic of neurofibromatosis type 1 (NF -1), it is suggestive of the condition as it is found in up to 30% patients with NF-1. So the physician should look for features of NF-1 in patients with a plexiform neurofibroma.
Jaw & Teeth
It causes a massive macroglossia that is progressive with advance of years and disturbs the patient's speech, occlusion, and tongue movements. [ncbi.nlm.nih.gov]
Derekoy et al reported a case of plexiform neurofibroma of the submandibular gland in a 20-year-old man with signs of Von Recklinghausen disease. 3 The patient also had macroglossia (regional gigantism). [ajnr.org]
- Subcutaneous Mass
In conclusion, considering neurofibroma (NF) as differential diagnosis for subcutaneous masses in head and neck area is critical for early diagnosis and treatment procedure. [ncbi.nlm.nih.gov]
Clinically, it presents as a subcutaneous mass which feels like a "bag of worms". Most of the time, it is a superficial cutaneous/subcutaneous lesion, but it can occur almost anywhere in the body. Symptoms may be related to local mass effect. [radiopaedia.org]
Multiple subcutaneous masses are seen in the right pelvic region. No abnormal bones or internal organs are observed. [journal.ac]
- Skin Discoloration
It is characterized by the overgrowth of nervous tissue and skin discoloration. [ncbi.nlm.nih.gov]
Hematoxylin- and eosin-stained sections showed unremarkable epidermis with slight hyperkeratosis. [ncbi.nlm.nih.gov]
Face, Head & Neck
- Neck Mass
Biopsy of the left neck mass confirmed for plexiform neurofibroma. A careful search of the literature revealed no previous report of such an extensive neurofibroma in a premature neonate. [ncbi.nlm.nih.gov]
Patient 3 is a 7-year-old girl who presented to our otolaryngology clinic at age 7 months with a large left-sided neck mass and café au lait spots on her right neck ( Figure 3 A). She later developed an optic glioma. [jamanetwork.com]
- Peripheral Neuropathy
Adverse reactions included transient somnolence in four, evanescent rash in two, and reversible mild peripheral neuropathy in two patients. Four patients showed less than 25% reduction in the tumor size. [n.neurology.org]
Peripheral neuropathy. 3 rd ed. Philadelphia: WB Saunders; 1993. p. 1623-39. [ Links ] 3. Nambi GI, Gupta AK, Kumaran S. Plexiform neurofibroma of the finger. J Plast Reconstr Aesthet Surg. 2008;61(11):1402-3. [ Links ] 4. Seddon HJ. [scielo.br]
- Motor Disturbances
Herein, a case is reported in a 56-year-old man who also had muscle atrophy, severe motor disturbance, and mild sensory disturbance of the left leg due to childhood poliomyelitis. [ncbi.nlm.nih.gov]
Beside history and physical examination, the workup of PN depends on radiological studies and histopathological evaluation. Ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) are helpful in the diagnosis.
Ultrasonographic appearance is a target shaped mass with a hyperechoic center and resembling a cyst. However, the mass demonstrates a continuous peripheral nerve and this finding is confirmatory of a nerve sheath tumor . Ultrasound cannot differentiate between a benign and malignant lesion.
MRI is the gold standard study as it is able to delineate the extent of the tumor as well as its origin from the nerve sheath . Plexiform neurofibroma appears as a lesion in the form of a target with hyperintense T2 and a hypointense central signal . MRI also helps to exclude sarcoma, schwannoma, lymphatic and venous malformations. In the case of a malignant transformation, the MRI will reveal an edematous zone around the lesion with cysts within the tumor while a tumor diameter exceeds five centimeters .
Positron emission tomography (PET) scan and CT scan can be performed if a biopsy is planned  .
- Marocchio LS, Oliveira DT, Pereira MC, et al. Sporadic and multiple neurofibromas in the head and neck region: a retrospective study of 33 years. Clin Oral Investig 2007;2013:165–169
- Ji Y, Xu B, Wang X, et al. Surgical treatment of giant plexiform neurofibroma associated with pectus excavatum. J Cardiothoracic Surg 2011;2013:119
- Murphey MD, Smith WS, Smith SE, Kransdorf MJ, Temple HT. From the archives of the AFIP: imaging of musculoskeletal neurogenic tumors: radiologic-pathologic correlation. Radiographics. 1999;19:5:1253–1280.
- Korf BR. Malignancy in neurofibromatosis type 1. Oncologist. 2000;5:6:477–485.
- Reynolds DL, Jacobson JA, Inampudi P, et al. Sonographic characteristics of peripheral nerve sheath tumors. American Journal of Roentgenology. 2004;182:3:741–744
- Fuchs B, Spinner RJ, Rock MG. Malignant peripheral nerve sheath tumors: an update. Journal of Surgical Orthopaedic Advances. 2005;14:4:168–174.
- Lin J, Martel W. Cross-sectional imaging of peripheral nerve sheath tumors: characteristic signs on CT, MR imaging, and sonography. American Journal of Roentgenology. 2001;176:1:75–82
- Wasa J, Nishida Y, Tsukushi S, et al. MRI features in the differentiation of malignant peripheral nerve sheath tumors and neurofibromas. American Journal of Roentgenology. 2010;194:6:1568–1574.
- Ferner RE, Golding JF, Smith M, et al. [18F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) as a diagnostic tool for neurofibromatosis 1 (NF1) associated malignant peripheral nerve sheath tumours (MPNSTs): a long-term clinical study. Annals of Oncology. 2008;19:2:390–394.
- Bredella MA, Torriani M, Hornicek F, et al. Value of PET in the assessment of patients with neurofibromatosis type I. American Journal of Roentgenology. 2007;189:4:928–935.