Abstract
A 49-year-old Japanese male with Lhermitte-Duclos disease subsequently developed a very rare association with Cowden''s disease. Partial tumor removal established the diagnosis of Lhermitte-Duclos disease. Follow-up examinations discovered the presence of Cowden''s disease. Long-term follow-up of patients with Lhermitte-Duclos disease is essential to identify signs of Cowden''s disease, which carries the risk of developing malignancy.