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Case Study 88 Leonidas Arvanitis, MD. Question 1:. A 27-year-old female complains of progressive muscle weakness of her right arm An EMG performed was suggestive of a “right ulnar blockage An MRI of the right arm showed an enlarged radial nerve A surgical excision was performed
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Question 1: • A 27-year-old female complains of progressive muscle weakness of her right arm • An EMG performed was suggestive of a “right ulnar blockage • An MRI of the right arm showed an enlarged radial nerve • A surgical excision was performed • Describe the histologic findings on the H&E stained section
Answer 1: • Abnormal segment of peripheral nerve with diffuse onion-bulb-like change • The cells appear bland, elongated and arranged in parallel bundles • No atypia or mitotic figures are identified
Question 2: • What other stains would be useful to make an accurate diagnosis of this lesion?
Answer 2: • S100 • EMA • Neurofilament • Click here to vie S100, EMA and NF stains
Question 3: • Describe the findings seen on the immunohistochemical stains
Answer 3: • S100 • Stains the axons in the center of the onion bulbs • EMA • The cells show diffuse membranous staining • Neurofilament • Staining is limited to enwrapped nerve fibers
Question 4: • Based on the histologic features and immunohistochemical profile, what is the most likely diagnosis?
Answer 4: • Perineurioma
Question 5: • How many subtypes of perineurioma exist?
Answer 5: • Intraneural perineurioma • Soft tissue perineurioma • Which includes the sclerosing type variant that typically presents as a solitary nodule on the hand
Question 6: • What WHO grade does intraneural perineurioma correspond to?
Answer 6: • WHO grade 1 • Click here to view a low proliferation index with a Ki67 immunostain