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 Table of Contents  
CASE REPORT
Year : 2017  |  Volume : 22  |  Issue : 1  |  Page : 34-37

Giant lumbosacral plexiform neurofibroma without associated neurocutaneous syndrome: An unusual presentation


Department of Radiodiagnosis, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India

Date of Web Publication14-Mar-2017

Correspondence Address:
Binit Sureka
Department of Radiodiagnosis, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi - 110 029
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jmgims.jmgims_41_15

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  Abstract 

Benign retroperitoneal and presacral neural sheath tumors of lumbosacral plexus in patients without Von-Recklinghausen's disease are quite rare with only few sporadic case reports. We report a case of giant unilateral plexiform neurofibroma of lumbosacral plexus extending into the thigh up to the level of knee joint in a patient without neurofibromatosis-1. Large unilateral retroperitoneal neurofibromas are rare while extension of the same up to the level of knee joint has not been reported yet. The purpose of the report is to highlight the characteristic imaging features in an unusual case of retroperitoneal neurofibroma extending up to the knee joint and thus avoiding unnecessary biopsy. Further imaging helps in defining presurgical extent of lesion, which in our case is essential as the lesion is seen extending along the entire course of the involved femoral nerve.

Keywords: Neurofibroma, plexiform, Schwann cell


How to cite this article:
Singh P, Sureka B, Mittal MK, Thukral BB. Giant lumbosacral plexiform neurofibroma without associated neurocutaneous syndrome: An unusual presentation. J Mahatma Gandhi Inst Med Sci 2017;22:34-7

How to cite this URL:
Singh P, Sureka B, Mittal MK, Thukral BB. Giant lumbosacral plexiform neurofibroma without associated neurocutaneous syndrome: An unusual presentation. J Mahatma Gandhi Inst Med Sci [serial online] 2017 [cited 2022 Dec 8];22:34-7. Available from: https://www.jmgims.co.in/text.asp?2017/22/1/34/202007


  Introduction Top


A neurofibroma is a benign nerve sheath tumor consisting of fibroblasts, schwann cells, and neural elements that expand and diffusely infiltrate the nerve and may occur as a solitary tumor or as a partial manifestation of Von-Recklinhhausen'sdisease. Neurofibromas have been subdivided into two broad categories: dermal and plexiform. Dermal neurofibromas are associated with a single peripheral nerve, while plexiform neurofibromas are associated with multiple nerve bundles forming interdigitating network of fingerlike fronds of tumor. We report a case of giant unilateral plexiform neurofibroma of lumbosacral plexus extending into the thigh upto the level of knee joint in a patient without NF-1.


  Case Report Top


A 32-year-old male presented with a history of gradually increasing dull pain in the right loin for 10 months and painless gradual increase in size of the right thigh since childhood in the surgical outpatient department of Safdarjung hospital. Abdominal palpation revealed a firm nontender mass in the right lumbar region with normal overlying skin. No family history of neurocutaneous syndrome was found. There was no evidence of any cutaneous stigmata of Von-Recklinghausen's disease.

Sonographic evaluation of the abdomen revealed multilobulated hypoechoic retroperitoneal mass lesion with linear echogenic areas interspersed within [Figure 1]. The lesion was seen displacing the right kidney anterolaterally with extension into the right hemipelvis and along the right femoral vessels into the right thigh reaching up to the right knee joint. No extension was seen across the midline.
Figure 1: Sagittal ultrasound image of abdomen shows multilobulated hypoechoic retroperitoneal masses (arrow)

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Computed tomography revealed a large well-defined retroperitoneal cylindrical-shaped multilobulated hypodense lesion in the right paravertebral region extending from the level of the renal hilum to the presacral and obturator extrapelvic space and along the course of femoral nerve beyond into the right thigh up to the level of the knee joint [Figure 2]. Multiple nonenhancing areas of cystic degeneration were seen within the lesion. Adjacent major vessels were seen displaced by the mass lesion [Figure 3].
Figure 2: (a) Coronal computed tomography scan image showing large well-defined retroperitoneal cylindrical-shaped multilobulated hypodense lesion (arrow) in the right paravertebral region extending from the level of the renal hilum to the presacral and obturator extrapelvic space of the pelvis and beyond into the right thigh through the obturator foramen (arrowhead). (b) Coronal computed tomography scan image showing the multilobulated hypodense mass lesion pushing the inferior vena cava and aorta medially (black arrow). Bladder is also indented by the mass (black arrowhead)

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Figure 3: Sagittal computed tomography image in bone window showing intraspinal canal extension of the lesion with foraminal widening and scalloping of posterior vertebral bodies at levels L1–L3

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To further characterize the extent, nature, and origin of the lesion, magnetic resonance imaging (MRI) was done. MRI revealed a large well-defined retroperitoneal heterogeneous T1-weighted (T1W) hypointense and T2-weighted (T2W) hyperintense multilobulated lesion in the right paravertebral region with similar extent seen on previous imaging [Figure 4]. In addition, MRI revealed the typical target-like appearance on T2W and spectral adiabatic inversion recovery images as central low-signal intensity nerve fascicles and peripheral high-signal intensity of collagenous matrix [Figure 5]a. T1W images showed mass as hypointense to adjacent muscles with variable contrast enhancement on postgadolinium sequences. The lesion represented the confluent multiple enlarged branches of the lumbo-sacral plexus. The fascicular pattern of nerve roots was intact with areas of cystic degeneration. Multiple thickened hypodense nerve roots were seen traversing through the right L1–L2 to S1–S2 neural foramina with resultant widening of neural foramina and causing smooth posterior scalloping of L1–L3 vertebral bodies [Figure 5]b.
Figure 4: Coronal T1-weighted (a) and sagittal T1-weighted images (b) showing the large retroperitoneal multilobulated mass lesion in the right paravertebral location (curved white arrow) extending from the level of the right kidney to the hemipelvis (line white arrow) and further into the right thigh (solid arrow). The extension of lesion is seen into the spinal canal at level L3 with widening of neural foramen and scalloping of the posterior aspect of vertebral body (solid white arrow, c)

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Figure 5: Axial T2-weighted images showing the mass lesion extension into the spinal canal at level L3 with scalloping of the posterior aspect of vertebral body (solid black arrow, a). Typical target-like appearance (centrally dark and peripherally bright) is seen within the lobules (line arrows a and b)

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Based on the imaging features, a diagnosis of giant plexiform neurofibroma was made. Biopsy was done from the lesion which revealed moderate cellularity with fusiform and elongated cells with many dark-stained nuclei embedded in collagenous matrix consistent with neurofibroma [Figure 6].
Figure 6: The tumor is characterized by tortuous proliferation of all components of peripheral nerves including axons, Schwann cells, fibroblasts, and perineural cells. This H and E stained photomicrograph (a) shows the typical appearance of a plexiform neurofibroma with multiple tortuous enlargements of neural elements. (b) Interlacing bundles of spindle cells with hyperchromatic wavy nuclei embedded in collagen matrix (H and E, ×100)

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  Discussion Top


A neurofibroma is a benign nerve sheath tumor consisting of fibroblasts, Schwann cells, and neural elements that expand and diffusely infiltrate the nerve. Neurofibromas have been subdivided into two broad categories: dermal and plexiform. Dermal neurofibromas are associated with a single peripheral nerve, while plexiform neurofibromas are associated with multiple nerve bundles forming interdigitating network of finger-like fronds of tumor.[1]

Neurofibromas are common tumors of peripheral nerves and can be found sporadically as solitary tumors unrelated to any apparent syndrome or as part of Recklinghausen's disease (neurofibromatosis type 1 [NF-1]).[2] There are at least eight subtypes of NF (NF-1–NF-8). Among these, Von-Recklinghausen's disease (NF-1), NF with bilateral acoustic schwannomas (NF-2), and segmental NF have been given more importance both clinically and radiologically. Both types of neurofibromas show an identical histological pattern consisting of Schwann cells, fibroblasts, and perineural-like cells. The affected nerve rootlets display an irregular enlargement, from which the term “plexiform” was originally derived. It is important to stress that plexiform does not imply involvement of a nerve plexus but implies a network-like growth of neurofibroma involving multiple fascicles of a nerve or multiple branches of a large nerve. When the tumor becomes larger, the following occurs: degenerative involution, hemorrhage and cystic degeneration due to vascular thrombosis, and subsequent necrosis.[2],[3]

Microscopically, the plexiform neurofibroma shows a chaotic array of wavy Schwann cell bundles dispersed in an extracellular matrix of mucopolysaccharide and collagen as neuronal axons pass into the neoplasm, they become widely separated by neoplastic Schwann cells and matrix. This feature distinguishes plexiform neurofibromas from schwannomas, which displace rather than assimilate the parent nerve.[4] This histological structure of the plexiform neurofibroma is particularly relevant when percutaneous or surgical biopsy is being considered. Because functioning neural axons are intimately intertwined within the tumor, sensorimotor nerve deficits can result as a complication of the biopsy. Grossly, the nerve enlarged by a plexiform neurofibroma resembles a rope, braided from the individual distended fascicles.[4]

The imaging characteristics of nerve sheath tumors depend on the relative amounts of fibrous and myxoid materials. This microscopic architecture could account for the centrally T2W dark (nerve fibers) and peripherally T2 bright (myxoid) appearances of the typical target-like appearance. Not all the plexiform neurofibromas have the typical target-like appearance. This sign can also be seen on ultrasound and is described as “sonographic target sign.” The absence of the target-like appearance should not speak against a lesion being a neurofibroma, particularly if the lesion has a superficial location. Another sign suggestive of neurofibroma is the “split-fat sign.” Neurofibroma in an intermuscular location is usually surrounded by a rim of fat which gives a split-fat sign seen on T1W images on MRI.[5],[6]

Giant nerve sheath tumor is a rare tumor originating from the nerve sheath. It differs from the conventional nerve sheath tumor only by the size these tumors can reach. The margins of the tumor are well defined, but apparent infiltration of adjacent muscles can be present which is not indicative of malignancy. These tumors may have an infiltrative, aggressive appearance radiologically and yet be histologically benign.[6]

In addition, it is important to consider NF as a differential diagnostic possibility when encountering an infiltrative and branching high-signal intensity lesion. These lesions may closely resemble a lymphatic or venous malformation or less commonly a traumatic or inflammatory lesion. Veno-lymphatic malformation can be differentiated on the basis of gradual enhancement, presence of phleboliths, lack of target sign, and widened neural foramina. Traumatic lesions such as retroperitoneal hematomas will only show peripheral enhancement with the absence of target sign. Inflammatory lesions usually have indistinct margins with variable enhancement.

The only current treatment of plexiform neurofibromas is surgery, but surgical resection is usually difficult because lesions are large and infiltrative. Recurrence is, therefore, common. In our case, the patient refused to undergo any surgical intervention.


  Conclusion Top


It is thus important to know the characteristic imaging features of giant plexiform neurofibroma. Biopsy may be avoided when the imaging features are classical.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Bass JC, Korobkin M, Francis IR, Ellis JH, Cohan RH. Retroperitoneal plexiform neurofibromas: CT findings. AJR Am J Roentgenol 1994;163:617-20.  Back to cited text no. 1
    
2.
Rieckmann K, Moreno IR, Rustenbeck HH, Hummel G, Verheggen R. Giant plexiform neurofibroma: An intraspinal dumbbell tumour with a huge retroperitoneal portion. Arch Neurocien 2006;11:18-21.  Back to cited text no. 2
    
3.
Fortman BJ, Kuszyk BS, Urban BA, Fishman EK. Neurofibromatosis type 1: A diagnostic mimicker at CT. Radiographics 2001;21:601-12.  Back to cited text no. 3
    
4.
Papageorgiou S, Litt JZ, Pomeranz JR. Multiple granular cell myoblastomas in children. Arch Dermatol 1967;96:168–171.  Back to cited text no. 4
    
5.
Bano G, Mir F, Beharry N, Wilson P, Hodgson S, Schey S. A novel medical treatment of Cushing's due to ectopic ACTH in a patient with neurofibromatosis type 1. Int J Endocrinol Metab 2013;11:52-6.  Back to cited text no. 5
    
6.
Ozcan HN, Karcaaltincaba M, Oguz B, Haliloglu M. Radiological manifestations of abdominopelvic nerve tumours seen in neurofibromatosis type 1. Clin Radiol 2014;69:431-5.  Back to cited text no. 6
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]


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