Soft Tissue Pathology
Reactive Lesions of the
Traumatic neuromas develop from a nonneoplastic proliferation of the severed, partially transected, or injured nerve as a result of trauma (lacerating or penetrating) or surgery (specially limb amputation).
Clinical presentation: Presents as a firm nodule that may be tender or painful.
Site: The most common location for traumatic neuromas is the lower extremity after amputation, followed by the head and neck (frequently in the oral cavity, because more than 50% of these lesions are related to tooth extraction). Other sites include the radial nerve and brachial plexus.
Traumatic neuromas have been divided into two major categories:
(i) Spindle neuromas are internal, focal, fusiform swellings secondary to chronic friction or irritation to a nondisrupted, injured but intact nerve trunk.
(ii) Lateral or terminal neuromas are the result of severe trauma with disruption or total transection of a nerve.
Gross: These lesions are circumscribed white gray nodules located in continuity with the with proximal end of the injured or transected nerve.
Traumatic neuromas arise 1–12 months after transection or injury, and vary in size with no malignant potential.
Microscopic features: Traumatic neuromas are nonneoplastic , nonencapsulated, poorly circumscribed lesions and is characterized by disorderly outgrowth of all normal components of a nerve fascicle.
The components include tangled masses of axons, Schwann cells, endoneurial cells, and perineurial cells in a dense collagenous matrix with surrounding fibroblasts.
The participation of all elements of the nerve fascicles distinguishes this lesion from the neurofibroma.
Differential diagnosis :
Palisaded encapsulated neuroma (PEN): Immunostaining with EMA reveals that in traumatic neuroma the individual fascicles are usually surrounded by perineurial cells, whereas in PEN the perineurial cells are observed mainly in the capsular areas and only rarely within the fascicles. Traumatic neuroma contains considerably larger amounts of collagen (types I and III), acidic mucin, and myelin products.
Morton's Neuroma (Morton's Metatarsalgia)
Digital Pacinian Neuroma
Rare lesion characterized by small extremely painful nodule on the fingers of middle-aged adults.
These lesions usually occur following trauma.
No recurrence is observed after surgical excision.
Microscopic features: These are uncapsulated lesions composed of abnormal aggregates of morphologically mature Pacinian corpuscles and intervening small nerves set in a fibrous backround. The corpuscles have a normal structure but are increased in size and number. S100 protein is positive for reactive schwann cells.
Differential diagnosis: Visit : Perineurioma - Intraneural perineurioma - The tumour is histologically composed by densely packed,small uniform pseudo-onion bulbs of EMA-positive perineurial cells surrounding central axon of schwann cells (S100 protein positive). In Digital Pacinian Neuroma, EMA is negative.
Nerve Sheath Ganglion
Rarely ganglions occur within nerve sheaths (intraneural location).
Cause: This lesion represents a degenerative process rather than a neoplasm.
Site: These lesions involve the large nerves about the knee (popliteal, peroneal,or tibial) at the level of fibular head.
Clinical presentation: Patients present with a palpable mass or neurologic symptoms resulting from nerve compression.
Microscopic features: These lesions show myxoid change surrounded by a fibrous lining and often occur in the connective tissue between the nerve sheath and the nerve, which often results in displacement of the adjacent nerve.
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