Amyloidoma of the brachial plexus.

BACKGROUND: Amyloidomas of the peripheral nervous system are rare lesions. Most commonly, they involve the gasserian ganglion and the branches of the fifth cranial nerve. No association with systemic amyloidosis has been reported. CASE DESCRIPTION: We describe an amyloidoma of the lower trunk of the right brachial plexus. At the age of 34 years, this 71-year-old female had undergone radical right mastectomy for breast cancer with axillary lymph node dissection followed by radiotherapy. On admission, she presented with burning pain to the right hand and mild motor deficit to the ulnar-innervated intrinsic hand muscles. A palpable lesion was found in the supraclavicular region. On surgical inspection, the lesion appeared to originate from the lower trunk of the right brachial plexus. The middle and upper trunks were dislocated. Histologically, fibrous connective tissue embedded small nerve bundles featuring perineurial and endoneurial fibrosis as well as amyloid. Amyloid featured immunoreactivity for both lambda and kappa chains. DISCUSSION: Localized amyloidoma of brachial plexus has never been reported. Because of compressive rather than infiltrative growth of the present lesion, a conservative surgery was achieved. Our immunohistochemical findings indicated that peripheral nerve amyloidomas are not, by definition, monoclonal in nature.