NEUROMUSCULAR CHORISTOMA (HAMARTOMA) WITH SMOOTH AND STRIATED-MUSCLE COMPONENT - CASE-REPORT WITH IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL ANALYSIS

Benign peripheral nerve tumors with a mesenchymal component are rare a nd are represented principally by the neuromuscular choristoma. We des cribe an 11-month-old male infant who presented with a mass arising fr om the left brachial plexus. The lesion was bound firmly to the involv ed nerves and consisted histologically and ultrastructurally of bundle s of well-differentiated smooth muscle cells intermingled with striate d muscle fibers and unmyelinated nerve fibers. In the 13 previously pu blished cases of neuromuscular choristoma, no smooth muscle component was observed. This unique peripheral nerve choristoma with not only st riated but also smooth muscle closely resembled neuromuscular choristo ma and was considered a variant of it.