Isolated nodular thymic amyloidosis associated with diplopia.

An 85-year-old man presented with diplopia and anterior mediastinal tumor that had enlarged during the preceding 4-year period. Computed tomographic chest imaging showed an irregularly shaped mass comprising two nodules (diameter, 4 cm) with calcification. Suspecting thymoma, we performed video-assisted thoracoscopic thymectomy. The resected specimen showed deposition of homogeneous eosinophilic and hyalinized material around the vessel wall in thymic tissue, and it stained positively for anti-λ antibody, indicating localized AL amyloidosis. There was no other organ dysfunction or symptoms and no evidence of systemic amyloidosis. Diplopia resolved immediately after thymectomy; however, the connection of diplopia with amyloidoma and thymic tissue remains uncertain.