R. NICKBRYANMDPATRICIA A.HUDGINSMD
Primary tumors of the peripheral nervous system are either neuronal or nerve sheath in origin. Neuronal tumors usually arise from the adrenal medulla or sympathetic ganglia. Most nerve sheath tumors are schwannomas (neurilemomas) or neurofibromas.
Schwannomas are benign nerve sheath tumors that arise from the Schwann cells of the nerve sheath. Twenty-five percent to 48% of schwannomas occur in the head and neck region.1 The most common site in the neck is the parapharyngeal space. These tumors are usually solitary, slow growing, firm, encapsulated, and smooth surfaced. They commonly arise from sensory nerves. Neurofibromas are generally encapsulated and are softer in consistency than schwannomas. They represent a combined proliferation of all elements of a peripheral nerve, ie, axons, Schwann cells, fibroblasts, and perineural cells, although Schwann cells are the principal component. Most Schwann cells have markedly elongated nuclei and pointed ends and are immunoreactive to S100 protein. Schwannomas, unlike neurofibromas, often show Verocay bodies, pallisading of nuclei, and hyaline thickening of vessel walls. The terms Antoni type A neurilemoma (compact spindle cell pattern with nuclear pallisading) and Antoni type B neurilemoma (looser arrangement with pleomorphic spindle cells and foam cells) are used to describe varying growth patterns in schwannomas.
Radiology Quiz Case 2: Diagnosis. Arch Otolaryngol Head Neck Surg. 2005;131(11):1028. doi:10.1001/archotol.131.11.1028
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