Final answer:
The tumor associated with myasthenia gravis is Thymoma.
Step-by-step explanation:
The tumor associated with myasthenia gravis is Thymoma. Myasthenia gravis is an autoimmune disease characterized by muscle weakness and fatigue. Autoantibodies against acetylcholine receptors in the synaptic cleft of neuromuscular junctions lead to myasthenia gravis, and Thymoma is often found in patients with this condition.