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Soft Tissue Tumors Part 3 - Muscle, Vascular, Nerve, Other
Neurofibroma - plexiform
Author: Nat Pernick, M.D, PathologyOutlines.com, Inc.
Revised: 2 June 2010, last major update - October 2009
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.
Definition
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● Benign peripheral nerve sheath tumor that surrounds multiple nerve fascicles
● Has irregularly thickened, distorted, tortuous structure
● Plexiform: complex; in the form of a plexus or network
Sites
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● Orbit, face, neck, back, inguinal
Clinical
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● Almost always develops during childhood
● Large tumors are attached to major nerve trunks in neck or extremities
● 5% transform to MPNST, a higher rate than classic neurofibromas
● Part of diagnostic criteria for neurofibromatosis type 1 (NF1) (Mod Pathol 1998;11:612), although occasionally isolated plexiform neurofibromas occur without definitive evidence of NF1 (Laryngoscope 2004;114:1410)
● 27% of childhood neurofibroma patients had plexiform neurofibromas in one study (J Pediatr (Rio J) 2007;83:571)
Case reports
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● Tumor of uterine cervix (Arch Pathol Lab Med 2005;129:783)
Treatment
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● Excision for symptomatic relief; often cannot completely excise the tumor
Clinical images
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Neck tumor Arm Hand Leg Leg
Mother with small neurofibromas on wrist and on legs present since her childhood
Cafe au lait spot on child's back and hand
Gross description
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● Associated with grossly enlarged and tortuous nerves
● Deep tumors are often large
● Often resembles “bag of worms”
● Highly vascularized and locally invasive
Gross images
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Other images: brachial plexus
Micro description
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● Nodular or diffuse
● Diffuse cases are also known as elephantiasis neurofibromatosa; characterized by an overgrowth of epidermal and subcutaneous tissue (Dermatol Online J 2009;15:7)
● Hypocellular with a myxoid background; contains Schwann cells, fibroblasts and mast cells
● Occasional nuclear palisading
● Rarely is pigmented due to melanocytes (J Am Acad Dermatol 2007;56:862)
● No biphasic pattern of schwannoma
Micro images
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Plexiform features
Uterine cervix Bladder tumor #1 #2
Contributed by Dr. R.F. Chinoy, Prince Aly Khan Hospital, India
Tongue lesion
Positive stains
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● S100 in scattered cells (unlike strong staining in schwannoma)
● Perineurial cells are EMA+ in plexiform but not in ordinary neurofibromas
Electron microscopy images
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Schwann cell processes enveloping collagen fibrils
Differential Diagnosis
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● Plexiform schwannoma (Am J Surg Pathol 1983;7:691)
End of Soft Tissue Tumors Part 3 - Muscle, Vascular, Nerve, Other > Neurofibroma > Plexiform
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