Granular cell myoblastoma arising from the thoracic sympathetic nerve chain.

Granular cell myoblastoma has been of interest both to the clinician and the pathologist for many years. This uncommon tumor presents the usual diagnostic problem of a mass, but the actual diagnosis of granular cell myoblastoma is rarely made prior to biospy. The origin of the tumor from either myoblastic or neural tissue remains controversial. Light and electron microscopic studies of a granular cell myoblastoma uniquely located in the posterior mediastinum and associated with the sympathetic chain support the neural origin of this tumor.